Reading this thread, thinking about all my various Yamaha power amps over the years and I suddenly thought, has Yamaha ever made monoblock amps?
Kenwood made them, Marantz made them, Accuphase made them, most US high end companies made monoblocks- why didn't Yamaha?
Or did they- I can't think of a model... Did they actually ever provide a bridging switch on any consumer grade amps? It's always a testament to the engineering of an amp if it has a bridging option as the amp is driving into half the impedance of the load.
Personally, my opinion of all Yamaha power amps from the M80 onwards are "fresh air amps". Massively large ventilated light cases, lots of space inside to look great on the sales floor, piss weak transformers, huge dynamic power- poor long term real power, lots of PSU rail switching (M85/MX1000 etc), big red meters and overall dry, lifeless sound.
I sold a heap of them (MX-xxx, CX-xxx) and have several languishing in my storeroom, but they never excited me. Great for parties, but not for serious listening.
That is an odd comment. Every now and then it seems that we are enamored by the glowing presence and nuggets of "wisdom" brought forth by one who has
"sold tons of X", and I admit that I'm often left wondering it this is some rudimentary justification to serve in building credibility where none otherwise exists. You see, anyone can say something bad about anything, and having never provided any reasoning behind their comments, those who come and read such are left to take it as truth. So, I am going to take a moment and give my experience, with honest qualifiers.
Your comment on the sound is relative to what media, source, preamp, speakers and room treatment was associated in the system. Any critical argument would make a mention of this before passing a baseless judgment. I have learned that every component in the audio chain is of utmost importance, and while none may be a weak link, so to speak, if it doesn't quite fit the balance and overall conjecture of the system, it can lead to negative impressions. Or, perhaps you simply did not like the sound. Some people like a fluffy transient response and the predominance of lower ordered harmonics - I know that I often do not. In this way, the MX-1000 have have a bit too much for your tastes by not offering enough tubby "musical" distortion. Fine and I suppose valid, but if one does not like the sound, they should explain why, rather than just how.
The comment on the transformers is a particular point of interest, as it seems to me that the MX-1000 had two very large transformers with copper faraday rings. It is often omitted from a discussion such as this, by E-cores, as used there, have a higher energy density than equivalent toroid. This does not imply that they are better overall, but were proper for the task. As Bob Carver and Nelson Pass noted, long term power is of little important in music programme, since the dynamic peaks are short term. Electro-pop crap will not be discussed because it doesn't constitute the demographic of audiophile repertoire. The 350W x2 Carver amp I once had, used a single transformer like something that we would see in a wall wart, and the Yamaha clearly shows better attention to design in my opinion with two large transformers - not that anyone should base their buying decisions on appearances or specifications. Audiophiles today are far to programmed into choosing gear based on brand, transformer size, chassis thickness, the prevalence of 20lbs aluminum face plates along with a host of things that they misinterpret. They should be using their ears, first and foremost. That brings us to the sound.
Your comments beg the question of if you have ever really used an MX-1000, or if there is something else at play here. I am quite familiar with its sound and several others in this thread, and your referral to it as dry and lifeless comes across as the
complete opposite of the sound that it offered here. For the sake of full disclosure, I once believed that the amplifier had rolled down bass and recessed highs, only to come and find it was the preamplifier that I was running at the time. I later moved on to a Mark Levinson/John Curl design, and the sound and extension was superb, not only in my opinion. The sound was detailed, full, quite expansive for a sub-$2000 1990's power amp, and was enjoyable. It was among my favorites for the reason that it sounded great in the system that I was using it in. It was sensible and the money was clearly put where it mattered the most- much like anyone who builds electronics for a living would know. Could it be bettered - of course - but at what cost, and where you willing to spend more?
I can only vouch for what worked for me, but in my opinion, Yamaha is an unmitigated risk for some. The name is not associated with high-end on audio forums, so has no resale value in the vastness of the brand-fashion conscience public eye, and there is the chance of being treated lumped into the low-end crowd of yesteryear regardless of well it performed. It doesn't seem to matter; the amps can be of competitive design, as they were, but as soon as the name Yamaha is stamped on the faceplate the owners are treated like a second-rate citizen for not running one of the more fashionable audiophiles names. The problem is, that public opinion today around what high-end is has less
and less each decade to do with sound or quality. I was always told that the Japanese made junk and nothing they made could drive less than 8 ohms, and I believed it at the time. The brand was never really on the radar, and the local megabuck crowd were pretty vague on anything other than American and (execrable) British made gear. It is a shame, because only after I learned that Yamaha made some higher end gear, would I come to also find it was among the most sensible built and best sounding amplifiers that I would use. There it is; I am no longer welcome among the high-end crowd. Not that I care...
Well that stands to reason, as HCA was real class A. Not that it would matter, they perform admirably.
The Titanium series MX-2000, and MX-10000 used advanced approaches for variable level fulltime Class A to maximum power. Bedini also did variable bias but it was rather simpler and more of a slow descending bias circuit. These yamahas are not push-pull like Pass' newer amps and Mark Levinson's gear, as upon closer inspection to the schematics we realize Yamaha's approach was with a mirror, two separate class A amps on each channel that could not become class AB.
Each amp employs two rows of Class A amps who's output was inverted to each other but with equal phase bias. One signal would then be inverted on one side, summed to the opposite, and the bias and distortions were current dumped and cancelled, not unlike balanced interconnects.
The input signal was referenced by the error correction amp, and used to further eliminate transient and harmonic distortion that may remain on its output.
The MX2000 and MX10000 will maintain a flat response into any load due to this servo, and was voltage biased in contrast to the current bias topology of other amps and this bias was modulated with the audio signal. I'm not sure about the MX1000, I know its Class A but to full power or not, I can't say having never owned one, but at its price what more could be expected? Word is, they sound super.
Think of the audio signal as acting Class A, but the class A being an active servo bias that itself was almost a transconductance (like tubes) Class C amplifier in character and followed the music, and an error correction amp to correct characteristics with temperature and load impedance variances.
And, that was one of the big considerations. Temperature coefficients would change the any class A amps specs wildly if the temp changed, again in the yamaha's its all servo controlled to correct this.
Intriguing technology hardly seen and easily mistaken as push-pull.
All of it had to be faster than the audio signal, which we know was fast and the amps stated bandwidth was 200kHz, but much higher. In the end the HCA allowed a small amp (well, they're actually pretty large) to provide bounties of power per channel into 1 Ohm without compounding constant bias as it reduced the duty cycle.
So what is it? Its two single ended quad class a amps on each side, with nulled distortion and music controlled bias. Nothing short of brilliant.
Great post, Mr. Jon Valin