Quote Originally Posted by 300A
I agree that the tube amp isn't very good in my opinion. But there is more to the story than the simple measurements told. Let me discuss some better designs and some problems with SS amps.

First, the distortion of the tube amp may be less than SS amps at one watt. One watt is what one uses most of the time. Transients can easily clip even a 100 watt amp, although the 'idiot" lights usually show the average. A tube amp may only have .005% distortion at one watt, while the SS amp may still have .02% or even higher at one watt.

Secondly, if the SS amp clips by only a watt or two, the distortion may rise to 10%.

Thirdly, the order of distortion makes a difference, and is noticed inversely as the order is increased. Thus 5th order is worse than 3 order, and 9th order is even worse than 5th order.

Next we have distortion caused by global feedback, which gives the low distortion figure using a simple sine wave. A simple sine wave, when fedback will result in a simple sinewave, even if it takes time to feed through the amp and then is fed back. The phase may be changed, but the distortion analyzer won't register this problem.

Music is complex with lots of different frequencies and their natural harmonics. The time it takes for the complex signal to feed through the amp and then feed back to the input doesn't coincide with the original input signal. By the time the input signal arrives at the output and is fedback, the input signal has changed. The higher the frequency, the more pronounced this problem is. But harmonic distortion is measured using a simple sinewave, not a complex signal, thus is useless when measuring this kind of distortion. And harmonic distortion figures are better with global feedback, even if they don't simulate real music.

Another problem is that frequency response can be artifically inflated when global negative feedback is used. You would be surprised how limited the frequency response is without feedback in many SS amps. However, the more feedback because of poor open loop response, the more "timing" problems you have.

So the specs given don't tell the whole story, actually not much of the story.

Most of the tests done by reputable reviewers run a square wave through the amplifier. Is it incorrect to assume that an amplifier that is passing a sqaure wave intact with no ringing is also playing all frequencies evenly across the audible sprectrum? And as far as the phase distortions you claim are utter nonsense. Do you realise what kind of phase shifts even the best of speakers have? Frequency response is what is important. Even a 1st order x-over is going to have a 90 degree shift. It's very simple. An amplifier with zero feedback is going to have extremely soft bass and a rolled off treble. If you like tube amps that's no problem. But please don't try and tell me that from an engineering standpoint that tubes are superior.