Originally Posted by dknightd
IMO comparing wine to audio is a mistake. Sure they both suffer from preconceptions. But the fact is most wine (or beer - my beverage of choice) does taste different.
Most good audio equipment sounds very nearly the same.
Good points. Of course speakers and rooms sound incredibly different, perhaps more different than different versions of the same wine. I think this may be why so many audiophiles think all components sound different - they hear so many of the different options in different rooms and with different speakers.
I'm not sure THD is a good measure.
With electronics THD isn't a good measure because as used, just about everything has either no audible distortion or distortion so low that it is really hard to distinguish.
I think some people like tubes because most of the distortion is even harmonics (kind of like what most instruments make anyway) whereas most transistors make both even and odd harmonics.
Actually transistor amplifiers being almost universally push-pull, have vanishingly low amounts of even distortion. Clipping is all odd order distortion. Tubed amps have odd order distortion when they clip, and often have lots of it below clipping. Since they typically have so much more nonlinear distortion, they almost always have more odd order distortion than a comparable SS amp
The story about people preferring even order distortion is probably at best a half-truth. Even order distortion is more likely to be masked by the ear (because most even order distortion is second order and thus closer to the fundamental and thus under its masking curve) and also by the natural sounds of musical instruments which are generally heavy on even order distortion.
Trouble is that THD is caused by nonlinear distortion which can't help but produce IM products as soon as two or more tones are present, which happens with just about all music. IM is primarily aharmonic which means that there are few naturally-produced tones in the music to mask it. Not only aren't IM products not masked and covered by the music, but they are generally at odds with the chord structure of the music. They just don't fit, and the ear knows that and gets unhappy.
I don't have a single piece of tube gear. But I have thought about adding a tube distortion on purpose - I don't think you can do that with an eq.
There is a way to add controlled amounts of various orders of nonlinear distortion in a way that is similar to what an equalizer does for timbre. It can be done with some DAW software (CEP/Audition for example), but it can also be done with a DSP in real time.
The problem with using natural distortion generators is that they have one profile of distortion generation, which you can vary in intensity by controlling the size of the signal passing through, but you can't change its internal order in ways that would allow you to spin knobs and get the distortion of your dreams or favorite SET amp.
Maybe you can with DSP.
For sure you can with a DSP or a PC. Just write a little code in C...
Some music I think might benefit by adding some nice even order harmonics (perhaps removed in a studio that uses too much eq).
Eq doesn't remove the effects of nonlinear distortion unless you are very, very intentional about what you do. Even if you are intentional most studio eqs can't do this well.
The best way to remove the effects of nonlinear distortion would be a nonlinear compensator, which is the technical name of what I was describing above. Nonlinear distortion can be cancelled out if you know what it is.
I'd probably only use it on things I thought were badly recorded, and then only very rarely.
I think you'd quickly find out about how much you can't adding IM when you add harmonics, and how much you don't like IM. IME while tubed equipment can have scary amounts of nonlinear distortion, that isn't their most audible effect.
The most audible effect of tubed electronics is IME the poor frequency response, particularly in power amps driving loudspeaker or loudspeaker-like loads. Read a Stereophile review of tubed amps. Know that Atkinson's speaker simulator is easier on amps than many if not most speakers. I studied the kind of loads many of the speakers he's tested, and came up with a speaker simulator that was about twice as stressful.
Tubed preamps are actually pretty clean, especially if you keep them away from SS amps with low input impedances and long cables. I have a CJ and its not at all that different sounding than my SS gear.
I'd like a simple switch - add .2, .5, 1 even order harmonic distortion. If nothing else it would be interesting to see if I could actually hear the difference.
Actually, that particular device has been built and its schematic is at:http://home.provide.net/~djcarlst/abx_grun.htm
(parts values for gvein amounts of THD at URL)
and looks like this: