Richard Clark $10,000 Amplifier Challenge - Why Couldn't Anyone Pass this Test??

Everyone knows that the difference between a violin and a viola is that a viola holds more beer.

yage
@geoffkait - Ah... didn’t see any links, so wasn’t sure that’s what you were posting about.

I think the conclusions were pretty clear, though: new violins sound quite good.

>>>>>Yes, either that or trained musicians are relatively tone deaf or whatever, which I actually prefer.

I suspect that what Shadorne calls ’difficult’ (and for that matter the author at the link Erik provided) is the simple fact that solid state amps (even ones known for driving difficult loads) can’t make as much power into the relatively high impedance that the Quad presents at low frequencies.

oh sure. Uh huh.

If this had any basis in reality, at all, speaker testing would be based on power vs. frequency. It isn't. It is input voltage vs. frequency.

Best,

E

Theory is too difficult to do in these forums, especially without graphs, but let’s talk some real world effects.

SoundStage Magazine online has a review for the Atma-Sphere MA-1 Mk II.2 mono-blocks:

http://www.soundstage.com/revequip/atmasphere_ma1ii2.htm

with an excellent set of measurements which to illustrate what the output impedance problem is with typical tube amps and how much it is.

The very first graph shows how the amp interacts with the complicated impedance of real world speakers. See the green line? That is what the electrical output looks like when driving a simulated speaker load. The frequency response can vary around +-3 dB (a bad thing) when driving an NHT:

http://www.soundstage.com/measurements/atmasphere_ma1_mkii2/

I think this is quite typical behavior for tube amps. Most solid state speakers would be quite flat, debunking the idea that solid state amps have a harder time, ever.

Despite the impression Atma tries to give, almost all speakers are designed as voltage-dependent devices. I know, I make them. :) That is, the prime quality we seek is to have a smooth and controlled frequency response for a given input VOLTAGE, not power. The power is going to vary up and down based on the crossover, drivers and even cabinet.

We like to assume the amps driving our speakers is what is called an "ideal voltage source." where current (and power) output will vary based on the speaker, but the output voltage is purely a function of the input signal. This gets harder to do with high output impedance amps, or low impedance speakers.

If your amp’s impedance is high enough, it will become an ideal "current source" where the output current has nothing to do with the load, and therefore the voltage at the speaker will vary wildly with the speker’s impedance. Atma-sphere has a unique perspective on this issue, and seems to constantly be suggesting a current source is ideal. He stands very much alone in this area.

That being said, the question of sound quality and amp/speaker matching is purely subjective, and you should listen for yourself. I'm pretty sure my favorite tube amps of all time, the CJ Premiere 8s were quite high in output impedance, but I'm not going to try to sell new physics to convince anyone to buy them.

Best,


E

The test is CD based. That might be why.