I worked at Audionics of Oregon as a summer job back in 1978. My duty was final assembly and packaging of their components, including their most successful power amplifier during their brief tenure on top of the solid state, high-end audio world, the CC-2. I would lock-tight a few nuts that clamp the power supply caps in place, hook up a few wires here and there, apply a silicone heat transfer compound to the heat sinks, screw on the lid (which also formed part of the heat sink), and the front panel (yes… also part of the heat sink) as well as the handles then box the whole thing up with a manual for shipping. Of course, one of the perks of working there was great employee pricing, so I got to own a couple of these beauties in my home audio system. And this 70 watts-per-channel “giant slayer” has never ceased to amaze me ever since.
I ran all sorts of different speakers with them, using them to show off the capabilities of speakers I had at the time in my home audio business. They ultimately found a home driving my “keeper” loudspeakers, the now legendary Magneplanar Tympani 1Ds (It’s all about reducing mass for the transducers). While the very difficult low-impedance load of the Tympani’s certainly made my CC-2s sweat, they always handled the task with aplomb, granted in the small listening room afforded by a teenager (Why do speakers need to be matched to room acoustics?…). One of the many, many things I learned while at my apprentice of sorts at AofO was how important the oft-overlooked amplification specification of “slew rate” (What is “Slew Rate” and why does it matter?…) was in order to properly drive most speaker designs without the decidedly unmusical effect of intermodulation distortion. AofO was the first US manufacturer to take a serious look at this and sacrifice their THD specs whilst many of their competitors ignored how their amplifiers actually sounded in order to participate in the “THD Wars” (The THD Wars – why lower distortion often doesn’t equal better sound quality.).
In my quest for audio nirvana in my Maui system, I was on the hunt for a CC-2 to drive my beloved Kef 104/2s (The Venerable Kef 104/2), which had already blown two vintage power amps in spite of their essentially benevolent character, albeit a bit on the low impedance side at 4 ohms (nominal). So I picked up an Audionics of Oregon CC-2 in Vancouver and disassembled it (because I know how they are built) into pieces that would fit into my carry-on bag for the flight. Yes, strange looks at security, but they let me through.
I honestly don’t think I’ve ever pushed an amplifier as hard as I have my now 40 year old CC-2 driving my Kef’s on Maui. I bought a spare for parts (cause you’re never gonna find the original Motorola power transistors on eBay) and with two CC-2s I had to try bridging them into mono, one per speaker. But that gave them fits as they don’t like the 4 ohm load when bridged in mono so I just choose the better of the two, left it in stereo, and have the other in storage just in case.
The CC-2 runs hot. And remember, the entire chassis is the heat sink for the power transistors so it can get so hot that you can barely even touch it. Yes… we’re talking frying pan hot, you could cook your eggs any way you wish on top of it. But this amp likes it hot. It actually sounds better that way. If it’s not breaking a sweat, it’s not happy. Not bad for an un-modified 40 year old, eh? I knew this about this amp from days past, but was still cautious at first. Then I was like, “it’s got this” and next thing you know I’m blowing fuses right and left (literally). Then… I remembered, the fuses are under-rated for what this little trooper of an amplifier is capable of and replaced them with higher rated ones (Blown fuse amplifier woes.)
If this amplifier was a person, it would be Clint Eastwood at his best, “Go ahead punk, make my day”. And in it’s “golden years” still Clint Eastwood but in Gran Torino style (an old, grey-haired guy who you underestimate at your own risk). All I know is there is no other power amplifier I’d rather have driving my Kef’s. All day, every day. The CC-2 and Kefs just dance so well together (Why do power amps need to be matched to speakers?…), which makes sense since Kef drivers were utilized in the speakers released by Audionics of Oregon at the time the CC-2 started production.
The CC-2 is also a perfect match for the 15 ohm Rogers LS3/5As (What is it about the Roger’s LS3/5A?…) I built in Canada, which also use Kef drivers (Kef T-27 tweeters and Kef B110 midranges). How do I know this?… Because I owned a pair of LS3/5As and listened to my CC-2 driving them back in the late 1970s – a legendary audiophile magic combination that most certainly wasn’t replicated with at least $10k worth of Bryson amps driving modern planars in a listening room at a dealer recently.
Who remembers how the THD (Total Harmonic Distortion) wars of days past nearly killed sound quality in power amplification circuits?… This was a far more insidious and localized demise than the certain-death sentence imparted by 16-Bit CDs. But it was an infections, tone-sucking demise none-the-less. So how can lower distortion be a bad thing? That requires a closer look at two things – what is being measured and how it’s reduction is being accomplished.
Harmonic frequencies (also referred to as “harmonics”) of a periodic voltage or current are components in the amplified signal that are at integer multiples of the frequency of the original signal. Harmonic distortion in audio circuits is the deviation of the amplified signal due to the presence of these harmonics.
In a perfect world (or in engineering terms a “perfectly linear amplification” world), a voltage or current that is purely sinusoidal has no harmonic distortion because it consists of a single frequency whereas a voltage or current that is periodic but not purely sinusoidal will have higher frequency components which result in harmonic distortion. In general, the less a signal resembles a sine wave, the stronger the harmonic components will be and the more harmonic distortion it will have. So a purely sinusoidal signal has no harmonic distortion while a square wave will have lots. Musical signals are never pure sine waves or pure square waves so… per usual, “the truth lies somewhere in the middle” of these two extremes.
Now let’s look at the harmonic distortion of these two waves.
So all the subsequent peaks at the harmonic frequencies of the square wave (blue) are distortions of the original signal and a bad thing. The total harmonic distortion (THD) is the additive effect of all these peaks so getting rid of them in audio amplification circuits must be a good thing… right?
The answer is yes, to a point. Part of the trouble with this method of measurement of THD is that it doesn’t account for how the human brain perceives it and account for the fact that the order of the distortion (which multiple of the fundamental frequency it represents) has a far more audible effect than its absolute magnitude. When three or more fundamental tones of distortion are present (in the illustration of a square wave above there are 10), the distortions represented by the higher orders are far more audible and undesirable, mainly due to intermodulation distortion (more on that later). This was first discussed by Norman Crowhurst and D.E.L. Shorter of the BBC back in the mid 1950s. They even advised a weighted measurement where the higher order harmonics accounted for more of the THD value, though this was never adopted.
Back in the days of tube amplifiers, THD was a very real measurement of sound quality and had a correspondingly high value by todays standards, often around 1% (the iconic Dynaco/Dynakit ST-70 tube amplifier was rated at <1% for example) . But with the advent of solid state electronics , it became far easier to introduce large amounts of negative feedback (60 dB or more) in order to drastically reduce THD, and many manufacturers did exactly that. Comparisons became more infinitesimal and the “THD wars” to drive it lower resulted in values below 0.1%, then below 0.01%, then even below 0.001% using op-amps (Op Amps are holding back my digital quest). In order to understand how this can be a bad thing, let’s take a look at how a simple negative feedback loop works.
According to Wikipedia, “A negative-feedback amplifier is an electronic amplifier that subtracts a fraction of its output from its input, so that negative feedback opposes the original signal.” In other words, it compares the output signal to the desired input signal and subtracts out any extraneous information (i.e. distortion). Sounds good… right? In a perfectly linear world, it would be. But real life isn’t perfectly linear and power amplifiers are no exception.
Negative feedback principles have been around for a long, long time and moderate amounts were implemented to good effect in tube amplifiers to some degree. But the over-application of NFB in audio amplifiers only became standard practice because transformerless transistor amplification circuits enabled its easy use. In the tube amplifier era it was the output transformer which, due to its complex transfer function, limited the amount of NFB in power amplifiers to around 20 dB.
So introducing strong negative feedback into inherently non-linear transistor audio amplification circuits has two significant flaws – far lower gain (often overcome by cascaded amplification) and the complications of transient intermodulation (TIM) distortion, especially in slow (low slew rate) circuits. Simply put, if a burst of a fixed frequency is input into a transistor amplifier with strong negative feedback, additional (unwanted) frequencies will be found on the output due to TIM distortion.
To obtain ultra-low THD specifications, manufactures of power amplifiers thereby killed the audio quality of their products. This explains why a low-fi Audio/Video Receiver (AVR) full of integrated circuits (ICs – Nude photos of analog gear usually tell a big part of the story) has a far lower THD specification than the best-regarded triode (i.e. tube) amplifier, even though any listener would invariably hear the better sound quality of the latter. In a sense, overuse of NFB in transistor power amplifiers was the beginning of the end of high end audio, followed by limiting the source material itself to 16 Bit PCM digital, then compressing this already inadequate signal to MP3 files as the final blow to music’s destruction (The “Dark Ages” of High End Audio).
This brief discussion is intended to point out how some traditional measurement results (such as THD) can result in unwise decisions for amplifier design. Unfortunately the THD wars of days past steered the designer, the reviewer, the dealer, and the consumer away from good sound. Nelson Pass, one of the very best amplifier designers of all time, has very strong beliefs with respect to how an amplifier should be designed, chief among these being that it is far more important to limit higher order harmonic distortion than it is to seek artificially low overall distortion levels. He also debunks the watt per channel (WPC) wars, but that’s another topic (Why it’s not about watts per channel).
Back in the 1980s, at the height of the THD wars, Nelson Pass developed a clever way to create a highly linear solid state power amplifier with his “Stasis” circuit topology and thereby was able to eliminate the use of negative feedback entirely while maintaining a THD spec of just 0.1%. Much higher than competitor’s offerings at the time but still inaudible and he thankfully stood fast against the overuse of negative feedback just to participate in the battle. Stasis was subsequently licensed by Nakamichi and implemented in their venerable PA-7, one of the best power amplifiers to come from the era (The Nakamichi PA-7 power amplifier). Audionics of Oregon is credited with producing the first US built low negative feedback, low TIM distortion solid state power amplifier with it’s CC-2 (The Audionics of Oregon CC-2. More distortion, more better.), which had a THD rating of 0.18% (0.35% when bridged into mono) and utilized only 23 dB negative feedback (very low by the standards of the time). This amplifier was based on the research of Matti Otala of The Netherlands, who pioneered the concept in 1973 and produced a prototype with a high slew rate of 100 V/microsecond, only 20 dB of negative feedback, low TIM distortion value of only 0.15%, and not surprisingly high THD of 0.2% (more info here).
“The bottom line is the ear is not a microphone, the brain is not a tape recorder, and measurements are limited in describing subjective quality. I like to have low distortion and so on, but these things take a back seat to what I experience when I listen. There are plenty of products which have great specs – I will not be offended if you buy those.” – Nelson Pass
Interestingly, the THD Wars have finally come full circle and many manufacturers of high end audio amplifiers (Audio Research, for example) are now advertising their products as having “no negative feedback” and their THD specifications are correspondingly much higher than their low-fi competitors. This is why it’s important to audition the audio gear you are considering, since the specifications are only an attempt to measure sound quality and… in the case of THD specifications that are driven artificially low with the overuse of negative feedback, a very poor one at that.
Even newcomers to the world of high end audio usually realize that when purchasing speakers, they need to find the right power amplifier to drive them. But when listeners shop for power amplifiers their main criteria is typically “watts per channel” and “total harmonic distortion” (THD – The THD wars. Why lower distortion often doesn’t equal better sound quality) and when they shop for speakers they often look at their power handling ability and/or what their rating is in “Ohms”. If speakers are rated for X watts/channel and they buy a power amplifier that is rated to produce X watts/channel than everything must be good in the world, right?… As usual, the specifications that are thrown around the most don’t tell the whole story.
Loudspeakers with a low “Ohm” rating are known to be difficult to drive, but how does this explain why the Rodger’s LS3/5As (What is it about the Roger’s LS3/5A?…) which are rated at 15 ohms and are very small “bookshelf” speakers will make a power amplifier sweat far more than a pair of 4 ohm large, floor standing Kef 104/2s (The Venerable Kef 104/2)? The answer is it doesn’t, there is far more to the story. In this case the 104/2s are a relatively efficient loudspeaker in spite of their large size and the LS3/5As are notoriously inefficient in spite of their small size.
Some speaker manufacturer’s have decided the power amplifier/speaker matching for you by including power amplifiers in their designs. Meridian is well know for this, for example. While this is a good approach in theory, it often falls short in execution and it limits the listener to their particular choice in speaker drivers. As far as I know, there are no self-powered planar loudspeaker designs for example, perhaps because the high-current power amplifiers required to drive them are so massive and usually tip the scales at well over 50 pounds each.
While planar speaker designs require massive power amplifiers, large but efficient speakers such as the Kef 104/2 can be driven nicely by a 70 watt-per-channel, 40 year old, small and relatively light Audionics of Oregon CC-2 (The Audionics of Oregon CC-2. More distortion, more better.) with aplomb. Why?… In part due to the high slew rate of this little beauty but also a synergy of sorts. Where specifications fail, listening tests come into play (listening tests vs. test measurements). Being far more subjective, it is the only way to be certain you have a good match for your listening room and music tastes. As such, demo your chosen power amplifier at home when ever possible. Failing that, try to audition it powering exactly the same speakers you own in a listening room that matches those in your home as closely as possible.
More techy details can be found at: http://www.sengpielaudio.com/calculator-AmplifierLoudspeakerAndOhm.htm
So, after having the Acoustic Resarch SP-9 (I may be a purist, but…) in my system for about a week, then the Threshold FET Nine (Threshold FET 9 Preamplifier) for about a week, I finally did an A/B comparison into my Maggie MG-12s – which are frigging PERFECT for my room (w/o tweeter attenuation) driven by the Nak PA-7. The front end was reference quality vinyl and both preamps got proper warm-up times.. The Acoustic Resarch SP-9 beat the FET Nine hands down (for my speaker/room combo anyway). Subtle, but very significant differences. Still need to do the A/B of the line stages with an SACD source, but the phono stage of that Acoustic Research is pure magic.
So Stax has been making headphones, or earspeakers as they prefer to call them, since 1960. That’s right… 55 years and counting as I write this. They have been the de-facto standard ever since, and most still consider them to be the best you will find if you need to throw some “cans” on your head. Interestingly, their technology has changed very little since their inception, which is why I’ve also included them in the “vintage” category, even though I purchased a pair that were manufactured in 2014.
They are still manufactured exclusively in Japan and if you want a pair you need to purchase from a dealer who imports them or import them yourself. I purchased the 4170 system, which ships complete with a tube headphone amplifier and the SR-407 headphones. But with Stax, nothing is as it seems and the headphones are actually mini electrostatic speaker panels (hence the terminology of “ear speaker”) and the headphone amplifier is not just an amplifier but also provides the high voltage these electrostatic panels need in order to produce music.
These ear speakers offer what is arguably the finest transient response, imaging (more on that later) and detailed frequency response available in a pair of “headphones”. Interestingly but not surprising, they also lack emphasis in the bass department, just as similar planar loudspeakers also lack it.
Unfortunately these Stax didn’t change my mind. No matter how you slice it there is absolutely no “sound stage” with headphones. They simply can’t project a stereo image in front of the listener wearing them so all the “imaging” happens between your ears and it feels and sounds like that. Not to mention that they are never gonna vibrate your listening chair.
Filling a room with music is a double-edged sword, in that room acoustics can very dramatically enhance or detract from the listening experience. But when properly set up nothing beats it. I can only speculate that those who prefer headphones likely have nearly impossible rooms to work with (which almost none are if loudspeakers are selected for the room – Why do speakers need to be matched to room acoustics?…) or their systems aren’t set up to take advantage of the room acoustics.
Another detracting factor of listening to music on headphones is the far greater potential for hearing damage, especially with an electrostatic version such as the Stax. It’s far easier to exceed the threshold to try to get better quality out of them. I noticed my ears ringing after a short session of listening to them at what I considered moderate listening levels by loudspeaker standards and haven’t worn them since. Try as I may, since it would be far more convenient with headphones, I’d rather just wait for opportune times to sit down in front of my loudspeakers.
I just committed one of the greatest sins ever in the world of audio amplification. I replaced both the 3 amp fuses in the output phases of my 35 year old Audionics of Oregon CC-2 power amplifier with fuses rated for 4 amps. Either channel would blow a fuse randomly, not constantly on just one side as one would suspect of faulty circuitry. The saying “you gotta know the rules before you can break them” comes to mind, and I’ll let you know if I eat these words later on.
So why would I so such a thing, you may ask? Well, I know these amplifiers very well. I worked at Audionics of Oregon assembling them, so not in an electrical engineering capacity by any stretch but I still got to know a great deal in this small manufacturing operation just by hanging out with the engineers at lunch and chatting with the service technicians on breaks. The venerable CC-2 is a fine, reliable power amplifier. It’s achilles heel has always been its relative intolerance for driving low impedance loads, it simply wasn’t designed with such design precepts in mind. It’s a high slew rate amp, and that makes in the perfect match for my Kef 104/2 box speakers (The venerable Kef 104/2). But, my Kef’s run at the moderately low nominal load impedance of 4 ohms, which is less than optimal for my CC-2 power amps.
But… I used to drive a pair of far lower impedance and far more demanding Magneplanar Tympani IDs with CC-2s. I even bridged them into mono on occasion, which taxes the power amplifier’s low impedance capabilities even further. But I found far greater benefit from the luxury of owning two CC-2s was to drive my Maggies passively bi-amped (Why bi-amping isn’t always what you may think). Did I blow fuses?… Yep, plenty. The CC-2 is known for having a very conservative fuse rating. Why?… AofO had a terrible failure rate on their previous generation PZ-3 power amplifiers. So much so that they were losing money due to the warranty returns. So I think the conservative fuse rating of the CC-2 was a sort of “knee-jerk” reaction to their history with the PZ-3.
I honestly can’t remember if I put higher rated fuses in the output phases of my CC-2s back when I first owned them in the 70s, but I’d be very surprised if I didn’t. If a fuse blows immediately when you power up your amplifier, you have a serious problem. If, however, your are happily enjoying your music at your usual listening levels w/o clipping and your amplifier heats up and eventually blows a fuse, you aren’t looking at an immediately catastrophic fault, but a far more insidious one.
I know from experience that it’s normal for my CC-2s get crazy hot (almost like a Class A amp) and they love it that way. All day, every day. My theory is that the fuses amperage rating varies with heat and as the fuses heat up their amperage rating goes down and they eventually blow. That’s my story and I’m sticking to it 😉 And, I’ve got a spare CC-2 should I blow a transistor or two, which aren’t so easily replaced as fuses are. That’s why I bought a couple CC-2s – because parts would be neigh on impossible to find and I know I’ll never find a better (sound quality wise) modern day replacement to drive my Kef’s, at least without a price tag well into 5 digits.
I’ve blown my share of power amps in my day. And I recently blew two sup-par vintage amps driving my Kef’s before I picked up the CC-2s. Back in the 80s I owned a Harmon Kardon Citation series power amp (which was built like a tank) driving a pair of Dalquist DQ-10s and came out of the shower to discover the cross-over network was in flames. I confess, I do like to crank it and yes I was guilty of cranking the music in the living room to listen to while in the shower.
It was far too late for my beloved DQ-10s (I would own a pair of those again in a heartbeat if I had the room for them), and the Citation was also toast. I wasn’t really in the mood for any DIY tinkering at the time, so I called the insurance company and they covered the smoke damages to thehouse (new paint and carpet), packed up the amp and speakers, hauled them away, and told me to replace them with pretty much anything comparable I wanted. I later got a check in the mail refunding my deductible, which told me they had successfully subrogated and had been paid back from either Harmon Kardon or Dalquist due to a manufacturing defect causing the fire, which surprised me.
While I don’t crank music in the living room to listen to in the shower anymore, I do love to crank it when I’m in the listening chair, especially classic rock. I know when my amp is breaking a sweat and when it’s not. I’ve pushed my CC-2s to the point where they are too hot to even place my hand on them, but I know they are OK. When they blow fuses randomly at moderate listening levels I also know they aren’t at fault, (under rated) the fuse is.
The Audio Research LS-3 Preamplifier (shown above) not only lacks tone controls of any kind, but it also incorporates a “direct” switch that bypasses the balance and selector switches as well, leaving only the volume control active. Audio Research has been in the high end audio game since 1970 and has been at the very top of the amplification food chain for nearly 45 years. They go to great lengths to fully preserve the integrity of analog signal paths, even in the necessary RIAA phono stage (see I may be a purist, but…). As far as I know, they haven’t provided tone controls on their preamplifiers since the SP-3, released in 1972. Why?.. Tone controls are, by definition, a degradation of an analog audio signal path.
In fact, any circuitry that is “incidental” to the task of amplification is a degradation of the signal path, and very little is essential. This doesn’t mean that what’s there isn’t important, but what’s not there is just as important. A volume control is necessary, as is a selector switch of some kind, phono stage circuitry for vinyl, and in most cases a balance control – both of my listening rooms require an increase of about 2 or 3 decibels in the right channel for proper sound staging, and source components are rarely perfectly balanced between left and right channels.
My Denon 103 phono cartridge (The formidable Denon 103 vs. 103R low output moving coil phono cartridges – is there really a difference?…) shipped with the left and right output voltages individually measured, and I discovered the lucky coincidence (even before I checked the hand-measured specifications) that the right channel output is just enough higher than the left to perfectly balance out my room acoustics (right channel output = 0.42 mV, left channel output = 0.39 mV). But that was just that, a lucky coincidence and it could have easily gone the opposite way, making a balance control absolutely essential (or swapping out the left and right channels and thereby reversing the sound stage).
Nearly all Japanese providers of high end audio components in the late 1970s and early 1980s took an opposite approach – the more tone controls and signal manipulations the better since you could use them to create a “flat” frequency response at your listening position in the room. Of course very few listeners used these controls to this end, but rather boosted bass and treble to compensate for inadequacies in either their sources, amplification components, or loudspeakers. Most Japanese components of that era even had a “loudness” control that performed the boosts (corresponding degradation of the signal path) at the flip of a switch. One look at this Sansui integrated amplifier made from 1970 to 1973 tells the story (Doing a little research on vintage Sansui for a customer…).
And who else remembers the elaborate “graphic equalizers” that became popular shortly thereafter?… Lots of lights and sliding controls to insure “proper” degradation of your signal path.
And, perhaps even more offensive to audiophiles, the original DBX 3BX signal processing unit that propurted to somehow, magically, create a delay in your 2 channel system (no 5.1 surround sound here) that simulates the acoustics of a concert hall… seriously?!
I was never a fan, and opted out but was definitely in the minority at the time. Don’t get me wrong, some of these units have a place in pro-audio for live performances in venues with acoustics that vary drastically from location to location, but that’s not how these units were being marketed when first released in the early 1980s (the DBX 3BX came out in 1982). They were “engineered” and sold to the home audio consumer market, and even some high end audiophile retailers began to adopt them.
Not to mention trashing your analog signal path, I also view the corresponding lights very distracting to the listening experience. I even go so far as to apply black tape over any unnecessary lights on my components (which is all of them – even clipping lights on power amplifiers assuming one can hear when their amp is clipping). Some manufactures recognize this and allow the option to extingish such lights (thank you Marantz DSD DAC), and some would rather make sure their logo or other bright (and sometimes even flashing) lights are prominent. Not to bash anyone here, but anyone who’s owned Emotiva gear is fully aware of the “Emotiva Blues” – their crazy bright blue lights, some incorporating their logo and not all of which can be extinguished. Ok, so I’m bashing. I could bash Emotiva all day on many counts, but I suppose they are filling a modern-day niche in the mid-fi market.
Difficult room acoustics can be handled in many other ways, certainly without modification of the analog signal path and most of the time without even resorting to expensive room treatment accessories (see How to upgrade your existing system without spending a nickel and A free upgrade for your planar speakers). I admit I’m a purist and listening to music is a personal endeavor and as such some may prefer drastic alterations to their signal path and accompanying flashing lights. If that’s the case I would respectfully suggest, however, not over-spending on source components, amplifiers, or loudspeakers since the extra cash for very high end audiophile gear is spent to fastidiously accomplish exactly the opposite.
This legendary solid state preamplifier is the mate for the Nak PA-7 power amp (The Nakamichi PA-7 power amplifier). It is also designed by Nelson Pass and follows the same precepts as his Threshold (and later Pass Labs) preamps and power amps, which is simple, short circuit topology with nothing but the highest quality fully discrete components in the entirety of the signal path. It lacks anything non-essential to that end, including tone controls of any kind (Why I prefer analog preamplifiers that lack tone controls). Nakamichi later released the CA-5AII, replete with tone controls, which makes the original CA-5A widely recognized as “the one to get”, even though the CA-5AII has a defeat switch it still adds additional, sound sucking and sound altering tone control circuitry.
One look at a “nude” photo of the CA-5A tells the whole story. Three beefy copper power rails running down the middle of it’s “dual mono” circuit board (which is important to reduce crosstalk between left and right channels, which compromises the stereo imaging), very short wire runs, very few circuit board traces, and nothing but top quality parts, including all ALPS for the controls (ALPS analog volume controls and rotary switches), and you can really feel the quality when you use them. Nelson Pass went on to separate the power supply into a separate chassis, which is the design in his Threshold FET 9 preamp.
The photo above shows the cartridge loading options I look for, including provisions for moving coil cartridges such as the Denon 103R (The formidable Denon 103 vs. 103R low output moving coil phono cartridges – is there really a difference?…). In fact, cartridge loading is the only slightly complex circuitry in this entire preamp, but is essential to top notch phono playback. Audio Research went so far as to eliminate the cartridge loading circuitry entirely in their SP9 Mk II preamplifier (I may be a purist, but…). Instead they, ship the resistors and capacitors necessary to change it with the preamp itself. While I agree with this approach in theory, in practice it’s a real pain in the ass to have to remove and replace (by soldering and desoldering) resistors and capacitors just to optimize your phono section for your chosen cartridge.
If you look at the schematic in the photo above you can immediately see how simple the circuitry in the Nak CA-5A is. The blocks labeled on the schematic diagram are even labeled on the PCB (Printed Circuit Board) itself. The Nakamichi CA-5A clearly subscribes to the “less is more” approach.
I’ve lusted after this power amplifier ever since it came out in 1988. It just looked so damn sexy. It originally retailed for $1,595 which isn’t a lot by today’s standards but certainly was back then, especially for a recent college grad trying to get ahead in San Francisco. So I never owned it and instead settled on the lessor Nelson Pass design in the form of the Adcom GFA-555II to power my Martin Logan Sequel IIs at the time. Well, I ultimately ended up with two GFA-555s powering those Sequel IIs and still wasn’t satisfied, but that’s another story (It’s all about reducing mass for the transducers).
So fast forward 26 years and I’m on the hunt for an appropriate power amplifier for my chosen Maggie MG-12s. This baby had been on Kijiji (Canada’s Craig’s List) for a few weeks for exactly half the original retail price, not bad 26 years later but still a friggin bargain for anyone comparing it to present new offerings. But it was in Edmonton, a 3.5 hour drive from Canmore. I ultimately decided to make the trip to have a look at the PA-7 as well as a couple other vintage high end audio components, which I also purchased (An Edmonton audio-venture (names changed to protect the guilty)).
So what first caught my attention about the PA-7 was it’s gorgeous build quality and industrial design, a fine example of industrial art (thank you Nakamichi).
I can remember like it was yesterday the first time I set eyes on this baby. It’s mesmerizing and belongs in a museum of industrial design. Let’s face it, brute strength power amps aren’t usually a thing of beauty, but this one is truly “beauty and the beast”. Everyone already knows that Nakamichi made it’s name on the very best quality home audio cassette decks in the late 1970s. So they had cash to burn, and wanted to become a major player in the high end audio market, which was dominated by US designers and manufacturers. So what do they do?… They recruit Nelson Pass (of Threshold) as a “hired gun” and combine his designs and circuit topology with their deep pockets and efficient production techniques. The result?… What is essentially a Threshold power amplifier but way better looking and less than half the price.
They were supposed to just license his STASIS technology, which combines the benefits of Class A amplification without the drawbacks (runs stupid hot = very low reliability) into a hybrid Class A/Class AB power amplifier with optical bias. Well, they didn’t just license STASIS. Rather, the first generation of the PA-7 is a direct copy of the equivalent Threshold amp. A lawsuit ensues, then Nakamichi releases the PA-7II with an altered design providing 25 more WPC (watts per channel) and a higher price tag. But everyone knew then and knows now that the original PA-7 was, “the one to get”. As a side note I also sourced a Nakamichi CA-5A pre amp of the same era which was also designed by Nelson Pass and executed by Nakamichi for my Maui system (The Nakamichi CA-5A preamplifier).
I found an interesting review on the now legendary PA-7 in Tone Publications, an online magazine I’d never heard of but certainly agree with the author’s findings. It’s interesting, since he ended up pairing the PA-7 with an Audio Research SP 9 Mark II preamp and a pair of Magnepan loudspeakers, just as I did. It all makes perfect sense in retrospect. I found myself there by time spent in the listening chair, not reading reviews, much as I suspect he did…
I love it when I see this kind of thing… So I’m doing a little research on the new Marantz DSD DAC (bought it… review here) and I see that it’s got a remote control, which makes me suspicious.
We all know that remote controls can spell disaster to high quality analog signal paths, so before I pull the trigger on this beauty, I’ve gotta know how it’s pulling off remote control of the volume, which is by definition directly in the signal path.
Many “audiophile quality” components pass this duty off onto an integrated circuit (IC) and I immediately call foul if that’s the case, so the internet search begins… Of course, no one else on the forums is looking at this. You can find out everything about this DAC from here to Sunday and a great deal about a lot of things that make absolutely no difference to sound quality. But try to find out this essential ingredient and it’s neigh on impossible.
So, I start looking at nude pics of the circuitry, which usually tells the story (Nude photos of analog gear usually tell a big part of the story). There’s nothing from any of the usual suspects on the USA forums, but I hit pay dirt on the Japanese ones (the general population of Japan just seems to care more… that’s why they came out with SHM SACDs (SHM SACDs – do they really sound better?). And, loh and behold, there it is in all it’s glory, an ALPS motorized POT (shown in the upper left of the photo), exciting!
Exciting you say? A 50+ year old technology (ALPS has been manufacturing volume controls and rotary switch since 1948) in a brand new, state of the art, DAC?… Absolutely! The folks at Marantz had the guts to concede that the technology of an era past far exceeds (in sound quality anyway), that of the present IC crap that fills all AVRs and even some “audiophile grade” components today. It’s the same APLS potentiometer (POT) used on on my Nakamichi CA-5A preamplifier from the early 1980s (The Nakamichi CA-5A preamplifier), just with a motor on it to facilitate remote volume control (yes… when you push the button on the remote it actually turns the volume control with a motor, which is awesome 🙂
After listening to my music server for several months now, there are things I love about it and things I’m not so in love with. I love the dead silent background during quiet music passages. I love the convenience though never seem to mind getting up to put a record on. I love the portability and the ability to travel with over 25,000 high definition digital tracks in a carry-on bag (two 3 TB hard drives). I’ve found plenty of high definition (DSD or 24 bit PCM) digital recordings that sound better than their re-released vinyl equivalent, since they were originally recorded and mixed digitally anyway.
What I’m not so in love with is what I can only describe as an “edginess” of even some of the finest “gold standard” DSD digital recordings (most PCMs lack some dynamic range and sound a bit “flat”, but that’s just the format). It’s mostly subtle, but still… there. I’m almost certain this is due to the op amps used in the output stage of my DAC. The DAC uses the best chip set currently available, dual mono circuitry, but cuts corners with op amps in the output stage.
When did it become acceptable for high end audio gear to use integrated amplification circuits?!… The answer is, of course, never. We’ve seen IC’s (integrated circuits) in audio electronics since the early 1980s, and if you pop the lid on any modern day AVR (Audio Video Receiver) it’s mostly ICs. This is an obvious trade-off of a typical AVR, you get lots of features, controls, remote control functions, and low cost in a single chassis and sacrifice sound quality for it. Fair enough.
But, when vendors are claiming to provide some of the best sounding components on the planet that cost well into 5 digits and I see ICs in there, I’m calling “foul”. I don’t care what their literature claims, I never heard a component full of ICs that I wouldn’t trade in a heart-beat for one that is fully discreet components. In fact, that has been the hallmark of my personal acquisitions. My Audio Research SP-9 MkII does however have two ICs, big kinda clunky looking ones (this was the early 1980s, after all), but they control ancillary functions and therefore are not anywhere near the fully analog signal path.
Integrated circuits that are particularly contrary to audio quality are op-amps. Integrated circuits that aren’t in the signal path may be OK, but amplifiers are by definition directly in the signal path. When I did some A/B comparison between my Marantz SACD player and my music sever running my Teac DAC playing DSD files I noticed the Marantz sounded better (DSD Music Server project), which was contrary to what I expected due to possible noise from the transport (i.e spinning disc) in the Marantz (What to look for in digital playback from disc).
Output stages are not complicated, nor expensive to manufacture with discreet components. To throw the whole circuit into an op-amp and “call it good” is simply unacceptable for high end audio, period. Marantz and Mark Levinson have tackled this deliema with discreet circuitry modules that have a similar footprint on the PCB (printed circuit board) as an IC, and sometimes even fit into the same pin configurations. Marantz calls this “HDAM” and claims to have invented it, but this isn’t anything new. All the output stages prior to the advent of the IC chip did the same.
Aftermarket vendors offer discrete component upgrades for some components (such as Oppo disc players) that plug right into the op-amp IC’s pin holes. Desolder and remove the IC, insert discrete circuitry upgrade. But why are we having to do this, when paying thousands of dollars for components?! There is definitely something wrong with this picture when seeing op-amp ICs in pricey audiophile quality gear. Enter the Marantz HD-DAC1, an under $1K DSD DAC offering top notch DAC chips and discrete output circuitry in the form of their HDAM. It just came out and is top of my list to give a listen, fingers crossed…
There is a really interesting and growing phenomena in high end audio these days, that of the “retro-cool”. Everyone knows vinyl is making a huge comeback, but whats interesting is that it’s recently also making a main stream comeback. Hoarded vinyl collections are no longer the exclusive domain of dedicated audiophiles. Extensive vinyl collections are showing up everywhere, from college dorm rooms (again) to trendy cafés in chic neighborhoods.
And what is the impetus for vinyl’s rebirth? Based on the systems I’ve seen at such venues, it’s not for sound quality. Many of vinyl’s biggest recent fans aren’t old enough to have loaded a CD into a tray and push play, let alone drop a needle in years past when that was the main way to play music. So it can’t be nostalgia since that implies having done it before and remembering it fondly.
That leaves the inescapable conclusion that it must be the “retro cool” factor. Like so many fashion trends that are being revived, so is vinyl. It’s amazing to me, that people are listening to music on vinyl records for the first time, in spite of (or possibly because of) the fact that they have never before listened to music in such fashion. It’s like the “cool, watch this, it plays music” vinyl revolution is some sort of mysterious new invention.
I’ve also noticed vinyl product placements in modern movies and television, and not necessarily in the context of the era portrayed. A scene from House of Cards comes to mind, when a modern day woman drops a needle onto a record to listen to music on an otherwise ordinary home audio system, then the camera zooms into the spinning record, or the many vinyl product placements in the Netflix TV show “Suits”, not to mention that the main character has filled an entire wall of his commodious office with records and has a high end (but not too high end as to come across as esoteric) turntable there to play them.
I had to scratch my head a bit over the vinyl product placements since the motive isn’t as blatant as when you see an obvious logo placement of a Dell, Apple, or HP computer, which is clearly paid for as a form of advertising (http://nypost.com/2015/03/02/house-of-cards-littered-with-product-placements/). Then it dawned on me. If the music industry (which arguably got hammered by the MP3 revolution) gets the next generation to adopt vinyl they will be able to sell the same music all over again in yet another “new” (old) format. So there it is, the profit motive. As usual, the music business follows the money.
But, there is a far less insidious trend in the industry in regard to the gear itself. At first glance the Yamaha integrated amplifier (Integrated amps or separates?) in the photo pictured above would lead one to believe it’s vintage (The vintage “crap shoot” ). Nope, just the styling is adopted from their amplifiers of the 70s. Nearly everything else about this amplifier is modern, and mostly in bad ways (integrated circuits and digital manipulations, Op Amps are holding back my digital quest). It makes sense to be sure, just as the auto industry is going for the “retro cool” look for so many of their latest offerings. They tried to sell us futuristic cars with side panels over the wheels (to make them look like they could fly?…) and other styling cues that impaired functionality. Form follows function and the most esthetic designs are always those that are true to their purpose.
So while I’m happy to see those idiotic flashing lights and elaborate displays on audio gear finally disappear, I can’t help but think the whole retro styling thing is a farce. What’s sad is that what’s inside isn’t what was inside from the era it depicts, when sound quality still mattered and a good stereo system was still central to home entertainment.
This is a really interesting article (to me anyway) about polarity. Back in the 70s we used to “opps” (reverse) only one channel of our phono signal polarity at the cartridge then reverse it back at the same channel at the speaker terminal. It therefore put once channel 180 degrees out of phase with the other through the entire, fully analog signal path until it got to the speakers. It was purported to speed up the amplification circuits. May have been smoke and mirrors or not, don’t remember, just remember doing it…
Personally, I prefer separates (preamplifier and power amplifier) to integrated amplifiers for several reasons. First and foremost, the power supply requirements are so very different, opposite really, for pre amps and power amps.
It makes perfect sense when you think about it. Preamplifiers are all about passing along delicate signals, not powering loudspeakers. Phono stages, and especially moving coil phono stages, are handling extremely low and delicate signals. My Denon 103R has an output voltage of just .32/.31 mV! (see illustration below – this is a scan of the hand plotted frequency response that came with the cartridge, thank you Denon!). If you’re intrigued by this, check out (The formidable Denon 103 vs. 103R low output moving coil phono cartridges – is there really a difference?…).
Such low signal levels can be easily and drastically effected by the strong EMI (electromagnetic induction) of even the very best power transformer. Imagine the 20 or 30 pound transformer found is some of the best Class A power amplifiers in the same chassis as this delicate signal… bad idea. Especially with the large, high current amplifiers necessary to drive the difficult impedance loads of planar loudspeakers.
Many of the high end preamplifiers go as far as to separate the power supply into a separate chassis with a long cord so you can place it as far away as possible from the signal circuits. Nelson Pass was one of the first to implement this methodology with his Threshold preamps from the 1980s. He even went even further by putting the phono sages in a separate chassis with yet another separate chassis for its power supply. Overkill?… In most instances, yes.
But it very dramatically illustrates the point of why having the pre and power amplification stages share the same power supply and transformer is such a huge compromise. That’s why you simply don’t see it happen in high end audio gear.
Ok… so this is a bit of an exaggeration, but in many instances it’s entirely true. If you want a purely analog signal path then there are limited ways to control the volume.
Once the analog audio signal is converted to digital, you have the ability to modify the volume all you want, as well as endless other digital manipulations. But converting a high quality analog source to digital for any reason is a bad idea. Converting it to digital just to change the volume without getting out of the listening chair is an extraordinary bad idea. I prefer analog preamplifiers that lack tone controls entirely to avoid any degradation of the analog signal path, but that’s another topic (Why I prefer analog preamplifiers that lack tone controls).
If you have a remote control in your hand, consider how it’s changing the volume. If the remote control is for a typical AVR (Audio Video Receiver), it’s most certainly converting signals to PCM digital to do so. If the signal is already PCM digital, no big deal you’ve already sacrificed analog quality. But if its the analog output of a DSD signal (such as from a high quality SACD player) or a high quality phono stage then beware, your signal will get PCMed just to have remote control of your volume.
Think about this for a moment… Say you have an amazing DSD recording from an exemplary source SACD. Then say you have a fantastic SACD player with the best DACs that fastidiously covert your high quality DSD stream to the very best quality analog signal possible (because you avoided an HDMI cable, right? –Just say “no” to HDMI). Then this signal gets ADCed (analog to digital converted) and what’s worse, that ADC puts it into PCM digital, and then DACed again from PCM digital to analog just for a volume remote control?!
While on the topic of DSD, it’s also important to note that if you are bit streaming native DSD from a music server you still won’t have a digital volume control. If you change the volume slider on your computer music server and the volume changes, it’s been PCMed 🙁
So, first and foremost, it’s essential to keep the volume control of analog signals in the analog domain. Let’s consider the two primary means to do this: potentiometers and attenuators. Potentiometers get a bad rap since they are used in cheap audio gear. Of course not all potentiometers are cheap and of inferior quality. In fact some of the best preamps made use high quality potentiometers, such as the ALPs found in the Nakamichi CA-5A (The Nakamichi CA-5A preamplifier). But when you notice a cheap, scratchy, analog volume control, it’s a potentiometer alright.
The alternative is a stepped attenuator, such as that show in the photo above. These use resistor ladders in order to precisely attenuate the volume in distinct increments. Most audiophiles consider these to be superior since they offer more discrete circuitry.
Both of these controls, however, lack a simple means to remotely control volume. For a potentiometer to have a remote control, it needs to be motorized, and that’s exactly what many high end audio manufacturers did as remote controls became more and more ubiquitous and expected. If done properly, this is a very effective solution to the dilemma of actually having to get off the couch to change the volume.
But attenuators lend themselves to digital manipulation, whereby a separate digital circuit is used to choose which resistors in the ladder go into the signal path and therefore attenuate the volume accordingly. It’s important to note however that in spite of having digital circuitry inside the preamplifier in order to intercept the signals from the remote control, there is no digital circuitry used in the audio signal path. It remains purely analog.
I’m sure you can see how both these solutions, especially the latter of digitally controlled stepped attenuators, gets pricey in a hurry. Therefore unless your preamplifier is accordingly expensive, it’s probably not using them. There are many, many purported high end preamps that are PCMing your analog signal just for volume control. Avoid them. Either save the $$$ and get out of your chair (my preference) or splurge on one that isn’t defeating high end audio in favour of convenience and price.
22Aug2016 – There is a recent development in audiophile volume control: Light Dependent Resistors. While it’s satisfying to see high end audio components pay closer attention to how volume control is accomplished, the cost is a bit disconcerting. I first noticed this technology implemented in the $65,000 Constellation Audio’s Reference Series Altair II / Line Stage, and for that price you don’t even get a phono stage. That said, you can’t beat the complete optical isolation this solution offers and the technology is already trickling down to more affordable preamplifiers, such as Tortuga offerings: http://www.tortugaaudio.com/saying-yes-to-light-dependent-resistors/
Setting the phono cartridge loading and gain on the Audio Research SP-9 MkII is a bit extreme, even for me.
The two beige resistors and the two silver/red capacitors shown in the photo above set the cartridge loading and need to be removed and different ones soldered into their place to change it. If you look up how to read resistor values you will see from the colour bands that these resistors are 47 kilohms.
And how do you modify the gain?…
See the extra lumpy solder bridging from “A” on the main circuit board to the other trace?… Desolder that. Luckily it comes shipped for high gain which is what I want for the Denon 103R LOMC (low output moving coil) phono cartridge anyway.
Acoustic Research explains this as resulting in better sound quality, which is certainly true in theory (less circuitry in the form of switches = better sound). But I’ll take the convenience of having some switches on the front over any very marginal gains in sound quality since what ultimately happens is that it’s such a PITA to change cartridge loading that very few do it and run their phono stage incorrectly instead (which would in theory be a far greater sonic penalty).
Having said that, Ive been running the ARC SP-9 MkII as it ships from the factory with 47k cartridge loading and unmodified gain with good success, even when I dropped in the Denon 103R. The SP-9 MkII is probably one of the few preamps that doesn’t say “MC” on it and yet has enough gain for the 103R.
The Threshold FET 9 in the photo above is a piece of cake by comparison, although the previous owner had never opened it up. It has dip switches for impedance and capacitance loading and jumpers for gain. Of course, you still need to know how you want to load your cartridge, but at least it’s easy to accomplish once you do.
“The focus then shifted to slew rate and TIM—low amounts of feedback and high-speed circuitry—the idea being that high-speed signals would somehow confuse an amplifier. People began building fast amplifiers and, lo and behold, quite a few of those fast amplifiers sounded significantly better. The interesting thing was that in order to achieve that higher speed, they had to make the circuits simpler. I don’t think it was actually a cause-and-effect relationship. I think that for the most part the higher-speed circuits sounded better because it took simpler circuits to get high speed with stability.”
Slew rate was the “unsung hero” of amplifier specifications up until that time. It is essentially a measure of how fast an amplifier responds to high frequency voltage shifts. In the illustration above, it is the delta T (time elapsed) that corresponds with the delta V (change in voltage), and is typically measured in volts per microsecond, or V/uSec. If you look at the sine waves in the illustration below, it becomes clear why slew rate is so important when it comes to frequency response.
As the frequency increases, the amplifier needs to be faster (i.e. higher slew rate) to produce the same voltage level. Many amplifiers of the late 1970s and early 1980s became bogged down by capitulating to the THD wars of the time and adding excessive negative feedback circuitry to that end. What resulted was a sluggish amplifier with great THD specs. In other words it looked great on paper but fell flat on it’s face when you sat in the listening chair, especially with traditional “box speakers” such as Kef’s made at the time. Not surprisingly, Robert Sickler listened to many of his prototypes on speakers made with Kef drivers, since Audionics of Oregon was using these drivers in their speaker designs. That’s why I consider my CC-2 amplifiers driving my Kef 104/2 speakers (The venerable Kef 104/2) a marriage made in heaven.
Nelson Pass has offered a great deal to the world of high end audio amplification, and one of the things I like best about him is he encourages DIY projects of his designs. This tells me he cares about the music deeply, above profit motives. Here in one of his prolific and open discussions he goes into cascode amplifier design (https://www.passdiy.com/project/amplifiers/cascode-amplifier-design).
He subsequently went on to introduce STASIS, which uses optical bias current and MOSFETs, innovations that are present in his Threshold Amps and the Nakamichi PA7, which is firmly based upon Nelson Pass engineering precepts (The Nakamichi PA-7 power amplifier).
Step up transformers (SUTs) and pre-preamps for low output moving coil (LOMC) phono cartridges can easily exceed $1k, but that’s part of the beauty of some vintage gear of a certain era when moving coil (MC) phono cartridges were popular, manufacturer’s almost threw in the MC phono stage for free. There are many variants from the late 1970s and early 1980s, including offerings from some of the major Japanese players of the day such as Yamaha, Nakamichi, Sansui and Sony. The Nakamichi CA-5A (The Nakamichi CA-5A preamplifier) is unique in that it incorporates a USA designed phono stage (schematic shown above), but is manufactured by Nakamichi. Which translates to a Nelson Pass MC phono stage nearly thrown in for free, which is exactly why I acquired it.
I had a friend interested in this integrated amplifier, the Sansui AU-9500 and I passed it off as yet another mediocre amplifier of the era. But my knee-jerk reaction to it was kind of bugging me so I did a little more research on this baby and even examined the circuit topology from the schematics (Circuit topology, why less is more).
Upon further investigation, this looks to be one of the best integrated amps the era offered and quite possibly the best integrated amp Sansui ever produced, hence the strong following. This amplifier was released when the owner and founder of Sansui (Khosaku Kikuchi) was on a quest to offer the best solid state amps in the world and this was his “no holds barred” TOTL (top of the line) flagship integrated model. In that respect it is a brilliant piece of audio history, probably why my friend was so drawn to it.
This amplifier was released from 1972 to 1973 only, and Khosaku Kikuchi subsequently retired in 1974. Although circuit design may have progressed in later Sansui integrated amps, it remains highly doubtful that sonic qualities improved, especially if such circuit designs implemented high negative feedback loops in the “THD wars” of the time (The THD wars. Why lower distortion often doesn’t equal better sound quality). In fact, the rather high THD of .1% on this model actually bodes well for its musicality and sonic potential. I doubt they subsequently made an integrated amp with better build and/or sound quality. And Khosaku Kikuchi’s goal to make solid state sound like tubes was certainly an admirable one, though that wasn’t really realized until the MOSFET amps of the early 80s came out, with the exception of the high slew rate/low TIM Audionics of Oregon CC-2 driving certain speakers (The Audionics of Oregon CC-2. More distortion, more better.).
The Japanese and US approach has traditionally been polar opposite in regard to the “less is more” or “more is more” approach, and Sansui obviously believes that by adding more tone controls you can achieve better sound quality. Hence the elaborate tone controls on the AU-9500, while US designers were going the opposite direction. Of course which is better is purely subjective, as are all things high-end audio. I am of the later camp and prefer not to have any tone controls at all, even just the usual “bass” and “treble” (Why I prefer analog preamplifiers that lack tone controls), which is the main reason I choose the Nak CA-5A (The Nakamichi CA-5A preamplifier) over the Nak CA-5A II. I’ve always found graphic equalizers, that became so popular in the late 70s, to be flashy tone suckers. But once again that’s just one guy’s subjective opinion.
It’s worthy to note that Japanese owned and operated Nakamichi contracted an American (Nelson Pass) as a hired gun for their circuit designs when they endeavoured to provide the world with the best amplifiers of the era in the early to mid 1980s, following their huge success in the cassette tape business. His circuit designs have always been extraordinarily simple, so that’s an indisputable indicator of where the chips ultimately fell, as are nearly all the modern high-end audio components that followed. I consider the Nakamichi amplifiers designed by Nelson Pass to be the best of both worlds from that era – fantastic circuit topology combined with Japanese build quality and stunning industrial design (The Nakamichi PA-7 power amplifier).
So the main concern I would have in regard to the Sansui AU-9500 would not be in regard to sound quality or its ability to drive just about any speakers desired, but rather due to its age combined with its complexity combined with the difficulty of finding places to get it competently serviced and it’s weight to ship. I would consider it a roll of the dice and while it may run another 40 years, I seriously doubt it.
As a side note the AU-9500’s direct coupled design is a rather bold move, indicative of their emphasis on utmost sound quality at that time. What it means is that without DC servo protection to shut things down in the event of a DC power fault feeding the speakers, it will destroy them in very short order. It probably has a DC servo protection circuit somewhere, but I couldn’t locate it on the schematics. The direct coupled design omits DC filter capacitors on the output stage due to their potential to adversely effect sound quality, which I find ironic given the proliferation of what I consider to be unnecessary circuitry in the circuit design to begin with.
I initially had concerns about the early 70s AU-9500 possibly being behind the design curve that came in the late 70s. But as previously noted, the high THD figure, coupled with the fact that they even mentioned TIM distortion in their specs, tells me that they were “on it” (in a good way) and trying hard to avoid that “first-generation transistor sound”, which makes sense as it was one of their stated objectives, to have a “tube-like” sound. I found this interesting since I thought Robert Sickler at Audionics of Oregon was one of the first amplifier designers to look at how negative feedback adversely effects sound quality and strove for high slew rate (What is “Slew Rate” and why does it matter?…)/low TIM distortion amplifier designs. The entire industry followed his lead, but maybe he was just one of the first American amplifier designers to look at it. Robert Sickler was also onto MOSFETs way before their time, but Nelson Pass later picked up that ball and ran with it to great effect.
Long story short, vintage electronics can often be a crap shoot, especially if you leave in a remote area, far away from service facilities (like Maui, for example). But mid-fi modern electronics, with their inferior build (and sound) quality are guaranteed to be crappy – they were designed and built in our “disposable age”.
That leaves a couple options. Pay exorbitant prices for quality modern gear, which will easily run well into five digits for each component, or try your luck with some extraordinarily high quality vintage gear from the “golden age”. Don’t get me wrong, vintage gear isn’t for everyone. I’ve done tweeter surgery (Trust your ears), retro-fitted cabinets to accept spec’d tweeters since the originals are no longer available, blown two power amps beyond repair, and fussed around with isolation platforms for turntables since their original vintage ones are grossly inadequate (Denon DP-790W turntable review).
But for those reasonably handy with a soldering iron and willing to do some DIY modifications and/or repairs, vintage gear can be a veritable gold mine. And, not all vintage gear requires tinkering, I’ve acquired three preamplifiers from the early 1980s (Nakamichi CA-5, Threshold FET Nine, and Audio Research SP9 MkII) and one power amp from the late 1970s (Audionics of Oregon CC-2) that are all performing just fine without any repairs or modifications what-so-ever.
Beware of over priced vintage gear however. Marantz had a classic styling that is fetching prices that simply aren’t commensurate with their sound quality compared to other vintage gear of the same era. Don’t get me wrong, I love Marantz gear and I also love their styling from the late 1970s, but you will be paying extra for that signature Marantz look and feel (see photo above). If that’s important to you than by all means go for it. A 1966 Jaguar XKE would totally suck on a race track by modern-day standards but is worth over $140k now since it is so collectable.
While a vintage Marantz receiver isn’t going to “totally suck”, it’s possible to find higher end components from the era at less cost. And separate components will nearly always out-perform integrated (Integrated amps or separates?). I used to sell these Marantz units back in the 70s when they were new and they were the bread and butter of my audio resale business (I was 16 years old at the time and worked at Audionics of Oregon after school and summers).
They have outstanding phono stages, great build quality, and descent power plants, were reliable and all wrapped up in very nice packaging with attractive real wood cabinets. That’s why they have become collectable and some sell for nearly 10 times the prices they did back then, as does a lot of the gear of that era. And… like so many collectable things, there is nostalgia associated with them and their distinctive styling.
So… I had an interesting day in Edmonton on the quest for high end audio gear. For some reason Edmonton is a major Canadian hub for it. Too bad it isn’t Calgary since that is a 1 hour drive and Edmonton is a 3.5 hour drive 🙁
Anyway, it’s really interesting to meet the people (all male of course) who are into this. They all differ on their motivations and aspirations. Every single piece of gear I’ve purchased here in Alberta (5 now) starts with meeting the wife in the nice cozy living room, then heading to the dungeon for “the goods”. The wife always offers me coffee, beer (if it’s past 6 pm) then disappears. It’s like this secret club or covert society. Fascinating. All good people, happy in their pursuit for what ever reason they are into it. So here’s an account of the day going down that rabbit hole:
Stop number one – Threshold FET Nine preamp, circa late 80s, MSRP then: $2,595 USD
So I pull up to this newly built, large house replete with thee- car garage in the boonies outside of Edmonton, on acreage, terrible architecture – big, two story turret faces you from outside as you enter and once inside, the room therein is clearly never used cause it’s the antithesis of “cozy”, designed to impress rather than express (the interests of the occupants). Classic example of what not to do from the book “The not so big house”, but I digress.
I’m greeted by the wife, who offers me coffee and I ask for water, then downstairs we go. But this in no dungeon, this i a very well laid out home theatre complete with huge screen projector – the kind of thing you see in HT magazines. He’s got a built-in cabinet on the left with a glass front that is filled from the floor to the ceiling with medium grade HT gear. On a bench placed in front of the sofa, which is in the sweet spot, sits an old Macintosh SS (solid sate) amp, circa early 70s, and the FET Nine hooked up to a low end CD player. The original box is off to the side, with hand written model and S/N on it, a good sign 🙂 He’s got some very nice Tannoy speakers, well positioned in the room (for a change) to listen to everything on.
So I start putting it through it’s paces, checking for crosstalk, hum, etc. This thing is perfect! I can already tell the phono stage has never been used cause there is absolutely no wear on the RCA jacks. This is going well… (unlike the Denon stuff I looked at in Calgary a week ago, but that’s another story). When checking for hum in the phono stage I’m hearing hum… but identify it as not coming from the speakers. He’s like, “oh, that’s probably the bar fridge” and I’m thinking to myself, seriously?! But… he’s obviously gotten away from high end audio, and is only into HT now, that’s why he’s selling it, which is a good thing, for me 🙂
So we listen to a CD for a very short while. I’m not evaluating since I already know of what this preamp is capable of, I’m just checking for obvious faults. Nothing so far 🙂 So I head out to grab my turntable out of the FJ. The turntable has an average at best phono cartridge in it. I assumed it was a throw-away but this is the first time I heard it and it sounded way better than I guessed. He knew I was interested in the FET Nine in part (a very big part) because of it’s phono stage so he knew I was bringing my turntable. I put on a MFLS OM (Mobile Fidelity Sound Labs Original Master) of George Benson Breezin (one of my reference’s). The opening sounds a little flat, but it always does, I know to expect that, then the steel guitar and vocals kick in and I bask in the goodness. I look over at the seller and his jaw has dropped, gazing like a deer in the headlights in disbelief. Then he looks over at me and stammers, “it’s like they are in the room with us…” It wasn’t turned up very loudly, didn’t need to be – that’s part of the beauty of high end gear. I head straight to the volume control (no remote here of course – Why audiophiles don’t get to have a remote control), turn it down and exclaim, “I’ll take it.” I can see by the look on his face that he doesn’t want to sell it anymore. He’s owned it for 25+ years and I honestly think this is the first time he’s heard what it’s capable of. It’s certainly the first time this famous Nelson Pass phono stage has had a signal passed through it. Amazing really.
I had brought a couple more MFSL OMs with me, but no need to break them out, I already know this thing is magic. And I’m thinking time isn’t on my side anymore and he’s likely to change his mind. Then, his wife walks down the stairs to check on us and offer refills of our drinks. Thank god for the WAF (wife approval factor). The seller says, “that’s amazing”, to which I reply, “yeah… but it’s a slippery slope and next thing you know you’ll be collecting records”. I look over at his wife Laura and she has a look of horror on her face and when he glances at her I know it’s a done deal and this piece of audio history is mine.
Before we box it I ask to pop the lid and look inside. I’m like, “there must be a cartridge loading dip switch in there or something”. I hadn’t researched this, but figured there must be. I also wanted to check for bulging capacitors, overheated resistors, crumbling diodes, etc. This thing is 25+ years old, after all. He had obviously never done this and it seemed sacrilege to him to do so. I dig around in the box and find, in the original little plastic bag, the 1.5mm allen key provided to remove the eight tiny screws and very carefully remove the top cover. I’ve been into high end audio for over 35 years and honestly have never seen prettier circuit topology or populated circuit board. All hand made of course. But obviously done so with complete pride and audio craftsmanship. Both the mother and daughter board are gold plated, all the capacitors, resistors, and other components are of the upmost quality, and the entire package looks like a gem box. Exemplary design, exemplary execution. No wonder this thing is collectable. We pack it up together and off I go.
Stop number two – Nakamichi PA-7, circa 1988, MSRP then: $1,600 USD
I can remember like it was yesterday the first time I set eyes on this power amp. It’s mesmerizing and belongs in a museum of industrial design. Let’s face it, brute strength power amps aren’t usually a thing of beauty, but this one is truly “beauty and the beast”. Everyone already knows that Nakamichi made it’s name on the very best quality home audio cassette decks in the late 1970s. They had cash to burn, and wanted to become a major player in the high end audio market, which was dominated by US designers and manufacturers. So what do they do?… They recruit Nelson Pass (of Threshold) as a “hired gun” and combine his designs and circuit topology with their deep pockets and efficient production techniques. The result?… What is essentially a Threshold power amplifier but way more sexy looking and less than 1/2 the price. They were supposed to just license his STASIS technology, which combines the benefits of Class A amplification without the drawbacks (runs stupid hot = very low reliability) into a hybrid Class A/Class AB amplifier with optical bias. Well, they don’t just license STASIS. Rather, the first generation of the PA-7 is a direct copy of the equivalent Threshold amp. A lawsuit ensues, then Nak releases the PA-7II with an altered design, 25 more WPC (watts per channel), and a higher price tag. But everyone knew then and knows now that the original PA-7 was, “the one to get”. As a side note I also sourced a Nak CA-5A pre amp of the same era and also designed by NP and executed by Nakamichi for my Maui system.
So… Enough history. Now it’s time to describe the seller. This time it’s a Polish guy who has a hobby building his own speakers. Not exactly an audiophile, but he’s a cabinet maker and a craftsman. He lives in a tiny one-story house and I’m greeted by him and his (hot) Polish wife, then downstairs we go. This time it’s truly a dungeon, no windows, star wars memorabilia, the “man cave” big time. There’s speaker drivers everywhere. No listening chair, a huge rack of gear that must stand 6.5 feet tall with a turntable on top that I can’t even reach and he’s almost a foot shorter then me – obviously there for show and not used (only a half dozen records on his shelves), all flanked by two pairs of huge home-made speakers. The set which are his pride-and-joy sport two sets of 15” woofers, huge horns for mid-range, and dome tweeters for high frequencies. I look over his design, all phase aligned and actually well executed, and offer (genuine) praise. He’s selling the Nak PA-7 cause he can’t tell the difference from his Carver, to which I offer no comment.
So once again I’m not here to evaluate this amp, but rather check for faults. I’ve already spoken with the previous owner and got it’s history and it’s all good. Kris (present seller) has thankfully only owned it for a couple months. Thankfully because I have the feeling if he owned it much longer something untoward would happen… to the amp, his house, or his marriage. He asks, “what kind of music do you want to hear?” and I reply, “how about some soft jazz”. He looks puzzled, as if he’s thinking to himself “what the hell are you looking at the PA-7 for then?!”, but just shrugs and goes over to play something from his “music server”, which I put in quotes since it’s a laptop playing FLAC files that originated from Redbook CD quality at best (44.1k/16bit). I listen for a while, everything seems to be working OK and his speakers sound pretty good and I suspect would sound really good with a descent front end. The only other things to do to test this power amp are to drive it to clipping and look inside, then I’m ready to buy it. I figure I’m never gonna drive it to clipping with my Magnepan MG-12s, as I would likely shred the quasi ribbons if I did so long before this amp cried “uncle” (side note – I’ve subsequently discovered this isn’t the case and I easily drive this amp to clipping with my MG-12s), so I ask him if he’s ever seen it clip. “Oh sure, he replies, you mean those little red lights?” I nod and he says, “Well, we gotta listen to something different for that.”
He puts on Dire Straits, Brother’s in Arms (the SACD version of which happens to be one of my references – lucky coincidence), then cranks the volume and looks over proudly at me as his speakers deliver seismic bass response and actually hold their own to everything the legendary PA-7 can throw at it. I’m starting to get uneasy as the room resonates and things start to vibrate off tables and shelves all around. I think of his wife, trying to watch olympic figure skating upstairs with her fingers crossed that I buy it. But… it’s still not clipping. He sees that and yells at me to wait for it, then notches it up a bit and the red lights flash away as the next bass line kicks in. I give him the thumbs up and he turns it down so we can converse once more. I said, “holy shit” and complimented him on his speakers once again. He was beaming and says, “yeah, I have to replace the light bulbs every few weeks since it rattles the filaments loose”. I said I’ll take it but want to pop the lid first, and he says, “sure, just give me a hand getting it out of the rack.” At nearly 70 pounds, this is a two person job. I ask him if he’s every had the top off and he says, “no” and I think to myself that’s probably a good thing. There a sticker on top that says “Lethal shock hazard. Do not open!”
The two of us box it up, original manual and original double box 🙂 He says, “I’m a cabinet maker, trust me it’s easier and better for your back if one person carries it. I’ll take it to the front door if you take it to your car from there.” I thought I’d got the better part of the deal since I didn’t have to carry it up the stairs until I got on the icy sidewalk outside.
Stop number three – Acoustic Research SP-9 MkII, circa 1987, MSRP then: $4,000 CAD
Third stop is at a high end store who is the second largest Audio Research dealer in North America, according to the salesman at least. I get inside and with seven listening rooms full of their gear, I’m not surprised.
He’s got the ARC SP-9 MkII sitting on the test bench, warming up nicely. This thing is visibly perfect, not a scratch and almost no wear on the RCA jacks. He pops the hood and shows me the inside. He’s particularly proud of the new tube he’s installed in the phono stage, which is an upgrade from the original and he shows me a link to it on ebay for $150. Now that the transaction’s done he proceeds to give me a tour of the store.
First we go to the uber-high-end room since I had asked about phono hum and how much was normal since it’s been so long I’d honestly forgotten. He points at a stack of large steel boxes on the floor with massive power cords into them, “See that? $20K worth of power conditioning, that’s how you get rid of hum.” Then he switches to the phono stage on the rack of the TOTL (top of the line) Audio Research gear feeding a floor standing Mark Levison amp located squarely between two large but not overly imposing cone speakers with (by peeking behind their cabinets) what I determined to be acoustic suspension design – almost zero hum as he inches the volume up to 104 DB. “I spent 4 hours setting these babies up” he beams as he turns the volume down, switches sources, and motions me to the capacious leather lounge chair located in the sweet spot and pulls up in an identical one next to it but just off centre. I’m thinking to myself, “this is gonna be a treat!” I don’t even know what he’s gonna put on and am especially pleased when I recognize Patrick O’Hearn chiming in at mid volume levels.
It sounds great, but then as I put my critical ear on I’m thinking to myself, “I expected more than this”. Then I hear some mid frequencies come in a bit hot and harsh and am already start to experience listening fatigue instead of closing my eyes and immersing myself in the music. I’m like, “Am I losing it?… Do I not know what high end audio sounds like anymore?…” Then I glance over at the rack and the huge ARC transport’s display says “CD” on it. He gets up (he’s been doing this for 30 years and knows how to read a listener’s reaction), turns it down and says, “You know, I never liked these Mark Levison amps”. The amp costs $30K and is not the problem. I know it, he knows it, but we both remain reticent. I don’t want to say anything and be insulting. He has to sell this stuff so he can’t say anything, but the tour moves on in short order. The only other source in the uber-high-end room is a floor standing turntable that sits about 4 feet high. It’s obviously not set up so I don’t even ask. No SACD player… strange.
I spent two more hours touring the remainder of the rooms, full of high end goodness, mostly turntables, and Mangepans everywhere. I told him of my experience testing various Maggies in a similar sized to mine (small) listening room in Calgary and he agreed that he didn’t care for the 3.7Rs. “Accurate to a fault”, I described them as, to which he replied, “exactly”. He shows me the HT room and points at a 5 channel amp and says, “watch this” as the lights flicker as he turns it on. “It runs off two dedicated 15A circuits. We’re wired for this and it still does that”. He shows me modern turntable designs and we go on about phono cartridge loading in preamps, and why the ARC SP-9 MkII he just sold me has fixed gain. I said that I’d remain unconvinced until I listen to it. I could have spent all day there, but it really is too bad the only thing we sat down and listened to was a CD player.
He liked that I knew about gear from the 70s and 80s and mentioned a pair of old Kef bookshelf speakers they had kicking around about a week ago. “They didn’t have T-27 tweeters did they?,” I inquired, failing miserably at not appearing excited. “They sure did. Are you thinking of building a pair of LS3/5As?”. He was on to me right away. “Yep, but they’ve gotta be SP-1032 version of the T-27s and Rodgers only accepted about 20% of the drivers from Kef as being within spec” I countered. That was true but I was primarily trying to drive the price down at this point as I knew he now knew he’d get top dollar from me for them. “We might consider parting them out” he said to which I replied, “do your research and get back to me with a price”. I already knew they are worth $200+ USD and figured why throw that price at him until he knows if he even wants to remove the tweeters from the speakers. That might seem like a lot for a pair of 40 year old used tweets, but worth every nickel if he’d sell them. I spoke of my Kef 104/2 restoration project over on Maui and of replacing the ferro fluid in the T33 tweeters on them. He knew exactly what I was doing and why, and called me “brave to tear those tweeters apart to rebuild them”. I told him I didn’t have them working again yet and was practicing on a pair taken from salvage 104/2s that were given to me by someone who was just so happy that someone actually knew what they are he didn’t care about the money. And, the WAF was present again in that instance, she wanted them out of the house (or even the garage).
Driving home back to Canmore:
And so, home I drove with my precious cargo of vintage audio gear. I was even careful over the bumps, like I had an FJ full of eggs in the back. And now the real fun starts. Where, finally after starting down this high end audio path once again around four months ago, I hopefully begin to reap the rewards of my efforts, and sit down and listen to music again. Something I will do almost daily once I’m able. And, what a journey full of interesting characters it’s been so far, even before I play (really play) my first record!
The first thing I do when narrowing down what high end audio gear warrants an “audition” is look at “nude pics”. By nude I mean with the case off so all the internal circuitry can be seen. High end analog audio gear is by it’s very nature, comprised of very few but very high end discreet components. Low end audio gear is typically just the opposite, with overcrowded circuit boards crammed full of tone-sucking, cheap integrated circuits (ICs), undersized transformers, and other cost saving measures.
Of course, “you get what you pay for” is a saying that comes to mind, but with modern high end audio gear it can be a confusing mix. Although there is (thankfully) a trend back to the “simpler is better” design precepts of vintage gear from the “golden age”, some companies still can’t resist adding a little “flash” and a lot of convenience by adding remote controls, which are perilous additions to any purely analog signal path (Why audiophiles don’t get to have a remote control…). So an easy way to shop for audio gear when it’s impractical or even impossible to give it a proper listen is to look at nude pics. Such was the case when I was looking to upgrade my DAC and stumbled upon the Marantz DSD DAC, which I couldn’t be happier with.
Even with digital sources, such as a high-def music server, you will want to maintain the integrity of the analog signal path once the best DAC chosen for the job has made the conversion from digital to analog, and nude pics can go a long way in telling the story prior to listening tests. One look inside the vintage and collectable Threshold FET-9 pictured above illustrates this point perfectly. Nothing but the best components very carefully and comfortable laid out in order to implement the circuit topology of the original design objectives. Threshold even went so far as to put the power supply in a separate chassis in order to further isolate the potential interference from the power transformer.
I was experience untenable hum in a behemoth of a vintage power amplifier and discovered what I had going on was a very dramatic ground loop.
I figured it out when I hooked up cheap speakers to the amp, turned it on again, and noticed extra hum and noise when I touched the SACD player, which was a part of the ground loop of course through the interconnects from the amp to pre-amp to SACD player.
That would also explain the blast of hum when the chassis touches anything (or anything touches it). Yes… it is that bad.
I ascertained it was a ground loop by “floating” the ground on the power amp with a 3 prong to 2 prong converter, but w/o screwing the ground screw to the outlet plate. Pretty primitive diagnostic tools, but hey… it worked!
As an aside, I’m definitely not gonna use the power amp with the adapter on the power cord, even though it does eliminate the hum by eliminating the ground loop. I just threw it on there for one power up to see if that was it and even used a plastic sharpie to push the power switch just in case the chassis was “hot”. Musicians have been killed by this very practice, but of course with multiple huge amps with floating grounds for live music. But I still don’t want to ever know what those caps are capable of, probably 20 to 30 amps at least I’m guessing.
Now that I know where to look, I’m guessing the power cord is old and restive, creating a voltage imbalance between the multiple grounds. V=IR and all 😉