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Can't wait to hear the results! Does he still have the deal where you've got to write up a 100 word review about them in order to get the special price??
Gary,I read through his technology section and although it was sprinkled with actual facts, I don’t think his assertions about positive feedback apply to _most_ amplifiers above $100. One of the most important aspects of an amplifier is its phase margin, which is essentially the phase angle of the output audio at the point where the gain of the amplifier reaches unity. So, phase margin = 180 – output signal phase angle (at unity gain). As he indicates correctly, if the amplifiers phase margin is 0 or positive at the unity gain point, the amplifiers feedback circuit essentially makes the transition from a stable negative feedback system to an unstable positive feedback system. Any decent amplifiers (certainly the ones you deal with) have extremely stable designs with PLENTY of phase margin. While its true that a circuit which could somehow detect the phase lag between the output and input, then scale down the input signal to ensure the amplifiers didn’t cross into positive feedback would help a poorly designed amplifier, I don’t think the amplifiers you are dealing with are affected by this. Now, I am not surprised that people hear a difference, since surely this device is altering the incoming signal in such a way to prevent what it deems as possible unstable feedback, but I suspect that there really is no point at which their amplifiers are coming close to an unstable feedback (phase margin >= 0). They are probably just hearing artifacts of a circuit that is incorrectly determining phase margin and altering the input signal when it shouldn’t be.There are devices that can measure an amplifiers phase margin, but I don’t know what they cost. We have one at work and even our cheesy amplifier designs have plenty of margin.Hope this helps,Mike
Also, I've ordered the patents in pdf version if anyone's interested. They should be up on my site soon.
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