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In Reply to: Tubes? Could anyone provide a concise list of virtues of tube equipment? posted by StylinLP on March 8, 2007 at 07:22:16:
If this even/odd thing is really the answer as to why tubes and transister sound different, how do we explain this? I just took a look at three SS pr-amp reviews on the Stereophile site, a Sim, a McIntosh, and a Mark Levinson. They all produce predominantly 2nd harmonic THD, nothing else rising above the noise floor. That seems to fly in the face of this theory, especially since most people probably wouldn't describe any of these pre-amps as tube-like.
Follow Ups:
Many tube amps have a high output impedance. You can easily check the technical reviews of amps at Stereophile.com or Soundstage.com to see the frequency response into the simulated speaker load.A significant article by E. Brad Meyer was published in Stereo Review, linked below.
____________________________________________________________
"Nature loves to hide."
---Heraclitus of Ephesus (trans. Wheelwright)
I agree with you, and have posted in the past my feeling that the output impedance of tube power amps, i.e. transformer coupling, contributes a lot to the tube sound. But in this case, I was specifically asking about pre-amps. I would think that the output impedance of a tube pre-amp, even if higher that a SS counterpart, would be low enough to minimze any voltage divider effect with the input impedance of the power amp it was driving.
Yes, the "odd order/even order harmonics" business really doesn't stand up as a distinguishing characteristic of one type of device vs. the other. For one thing, that difference is often characteristic of a single-ended vs. push-pull output circuit, with either type of device. Push-pull circuit suppress even order harmonics.One pretty clear difference is in the way the two devices handle overloads -- which accounts for guitar players' preference for tube amps. But, one would think a competently designed amplifier would not, under ordinary circumstances, be driven into overload.
The truth is generalizations are pretty useless because circuit design is such a big element in what the "sound" is with either type of device.
I think what the other posters pointed out is that modern day amps are done so well that you can't classify any of them anymore like we used to. I remember back in the late 90's people on here used to easily run a list what a tube amp can do vs any ss amp.
I've been reading hardware reviews in Stereophile and Absolute Audio for 5 years straight now. I noticed that SS amps now are breaking down all those barriers.
_______________________________________*Analog fans may be blind-but digital fans are deaf*
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