CLASS A AMPLIFIERS

highly biased Class A operation

This is probably Mr Pass' way of saying the device is operating in "deep class A". Just the PS is well over the expected 4x the energy output rating fro class A.

I think I read somewhere that this is acharacteristic of pure class A amps in general and that it also applies to tube amps. If I remember correctly, and I am getting old, I believe CJ told me that it was a characteristic of my premier 11a, but I am not sure. The topic came up with CJ when I was asking them questions concerning tube amps and driving thiel speakers. I maybe speaking to much to generalities and not enough to specific circuit topologies.

Chuck

Czbbcl , that is not a characteristic of class A amps although this may be a limitation of Pass designs. As stated above Gryphon class A amps double output from 150W @ 8ohms all the way to 2400W @ 1/2 ohm (5000W peak). In the real world your home electrical circuit will be the limiting factor with well built true class A designs with HUGE power supplies. - Jim

Real Krells can double down and down again from their rated power. I'm not sure if they maintain full Class A operation as they do. I sure would like to find out though.

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