CLASS A AMPLIFIERS

I have a question whether or not the amp I own differs from those statements made above. Can someone tell me whether my belief that my amp runs Class A all of the time is correct or not. I have had one or the other of these units for years and always thought such was the case.

I own a vintage (1979) Yamaha MX1000U amp and had the MX10000U prior to that. Yamaha states that their Hyperbolic Conversion Amplification Circuit (HCAC) "eliminates the only serious drawback of previous Class A operation amplifiers. These had to switch to non-linear Class AB operation above a certain load current, causing a slight deterioration in the otherwise excellent sound quality. The HCAC does away with this problem, allowing the Yamaha MX1000U to deliver superior performance constantly, without switching or cut-off, over its entire power range.

Advanced Power Supply Circuitry (APS) power supply is also incorporated in the amp. The problem with conventional power sources was their tendency to produce pronounced voltage ripples during medium to large amplitude music signals, particularly under low impedance loads, together with voltage fluctuations in the power transistors. APS solves this problem by providing an active power source that ensures stable voltage in the final transistor stage under all operating conditions, thus greatly improving power supply to the amplifier."

Minimum RMS Output Power Per Channel:
0.003% THD, 8ohms - 260w
0.007% THD, 6ohms - 295w
0.02% THD - 330w

Dynamic Power Per Channel (IHF):
8ohms -- 450w
6ohms -- 560w
4ohms -- 740w
2ohms -- 960w
1ohm -- 1000w

Dynamic Headroom:
8ohms -- 2.38dB
6ohms -- 2.78dB
4ohms -- 3.51dB

Power Band Width: 0.03% THD 130w, 8ohms -- 10Hz-60kHz

THD Main In to Sp Out, 130w/8ohm = 0.003%

Intermodulation Distortion (rated output/8ohms): 0.003%

Signal to Noise Ratio (IHF-A-Network)
Main In 9 shorted) -- 126dB
Main In (5.1 k terminated) -- 122dB

Residual Noise (IHF-A-Network): 21uV

Thanks

Wow, I wonder if Ken Stevens would upgrade my CAT amps with that APS technology! Oh yes, the 1970s and their super huge spec sheets. Those were the days when all amps measured very differently but still sounded the same. And now today everything still measures very differently but sounds wildly different. Hmmm, what happened? Man oh man I miss Julian Hirsch.

Aldavis

The attached website (http://sound.westhost.com/class-a.htm) has a pretty good explaination of class A amplification form a lay persons perspective. I believe the Gryphon is designed as a push-pull topology (unsure) versus the Pass which is a single ended topology and depending on ones definition of pure class A the Gryphon may or may not fit the bill. But again I am not an expert on the subject.

Unsound I believe krell is a class a/b design

Chuck

Chuck, all early Krell's were Class A. Some newer ones (IMHO the only real Krells) are as well, but, use their proprietery sliding bias scheme. I still think these sliding bias amps can make good on their Class A claim. The very early Krells used fans, the later ones used massive heat sinks and the newer ones sliding bias, (still pretty hefty heat sinks as well).

Unsound

I went to krells web site and he states class A topology. It would be interesting to know if it is push-pull, single ended or what specific design they are.

Chuck