How close to the real thing?

Mapman, -- "not all distortion is necessarily unpleasant" , I agree with your comments 100%. And, there is definitely "nice" distortion, which is quite easy to do, and is a perfectly valid way of obtaining listening pleasure. One of my earliest high end experiences was listening to a dealer's highly tweaked in home setup, we are talking here of Goldmund Reference TT, Audio Research D250, Infinity columns: of course the playback on a selected LP was absolutely stunning. He didn't like CD, of course, but had a CAL, so I tried one of my "test" CD's. The experience was bizarre, sounded smooth and pleasant enough, but half the sound content had disappeared! My half reasonable setup of the time at home absolutely walloped his in terms of conveying the musical message on that particular CD.

So "nice" distortion works, but it is "horses for courses" ...

Frank

Tubes and transistors seem to act very similar to feedback. I've less experience with class D, but from what I am seeing there are several techniques of using feedback and some work better than others, so it would be unsafe to generalize that feedback works in all class D amps without increasing odd ordered harmonics. In some it seems to work well though.

Not heard one yet that images as well as I am used to but I've not heard them all either.

Weseixas, Timlub, thanks for your reaction and comments to Atmasphere and Mapman, they are coming from very close to what my take on the situation is.

What I hope to inject into this conversation is something that for me has been very intriguing and frustrating over many years. That, which all hard core tweakers know, is that fiddling with any and everything makes a difference, and my reaction has been, what the hell is going on ?? Agreed, the topology, or circuit type of the amplifier can make a big difference, but once you improve your amp, then you more clearly hear the effects of making changes to other components, and the impact of everything else becomes more significant. Hmmm... not sounding too good at the moment ... gee, I wonder if that fluorescent light outside in the garage is on or off?

The trouble is, that last sentence is NOT funny, because it's true! Again, everything matters, and why does it matter? Because all the little, little things alter the makeup of my "micro" distortion, and the ear/brain has no trouble, no trouble at all picking up the change. It may sound better or worse, but it will definitely sound different!

Distortion can be linear, that is, altering the frequency response and phase angles, or nonlinear, which is everything else. The latter is the "baddy", big time: my experience is that if you minimise nonlinear distortion then linear distortion becomes totally benign, and the ear/brain can dismiss it as irrelevant. I've had a very ordinary amplifier (Sony) with classic tone controls, and managed to get the overall system working extremely well; then wound the bass and treble fully up and down, and I couldn't hear anything happening to the sound! Why, because the ear/brain could reject those changes as being unimportant to the musical message, enough "good" information was coming out of the speakers to compensate for a change that would normally be very obvious.

Yes, feedback is somewhere in there. But there is correct feedback, and "bad" feedback! If feedback was inherently not good then no piece of recorded music could ever be made to sound good, since every recording device and studio is riddled with feedback design techniques and circuitry, going back to almost the very start of electronic recording.

The quip earlier about the light points to a key factor that people play around with: power supply quality, or maybe, maybe it's RFI!? The trouble is, it's all very messy, but it ALL has to be taken care of!

Why should one? Because, if you do, then the level of "nasty", NOT "nice", micro distortion is reduced to the level that the ear/brain says "Yes! I can now accept this as being a thrilling experience, I won't be fatigued no matter how long I listen, it's magic, it's real!". And the convincing soundstaging, etc, automatically follows ...

Frank

Atmasphere, there is no way that well-designed solid state amplifiers "tend to have these higher odd orders all the time. This is one of the reasons they tend to sound hard or bright. Now its important to note that these harmonics do not have to be very distorted, usually 100th of a percent are audible, simply because these harmonics are so important to the human ear." Total harmonic distortion, meaning any and all spurious frequencies away from the fundamental, is normally at about -70db or better, usually better, and there's no way that such low-level distortions could possibly cause amps to sound hard and bright.

The most likely cause of hard and bright sound are no-so-good speakers, that have too much upper midrange energy when driven by an amp with a low output impedance and flat frequency response. Connect a tube amp with a rising output impedance in the same frequency range, which will cause a roll-off in the overall response, and voila, hardness suddenly gone.

Irvrobinson, I would agree with you about those distortion levels, but certainly would not blame the speakers directly. I would suggest rather that the combination of equipment and setup is allowing other distortion mechanisms to intrude, into the electronics of amp and CD player, say. Typically the power supplies of much equipment are pretty hopeless in suppressing interference into sensitive areas, and this is the sort of thing that normal THD measuring never captures.

So, either you boost the quality of the power supply, as, say Naim does, or you cotton wool the power being fed to the gear with filters, special power cords, etc, etc.

Frank