What determines good distortion?

Distortion is distortion. When you hear or/and feel it, it's bad. Whether it is tube or ss doing it, I have low tolerance.

The odd-ordered harmonics (above the 3rd) are used by the human ear/brain system to ascertain the volume of the sound being heard. This is pretty important to know if you want your system to sound like real music rather than a hifi.

If an amplifier has troubles with this, there will be two results- it will sound louder than it really is, and it will sound brighter than the music really is. All human ears are very sensitive to this!

The ear hears harmonic distortion as tonality. Electronics can have the fault of being overly 'warm' in sound, which is caused by the 2nd, 3rd and 4th harmonics. Quite often tubes get taken to task over this, but that really has more to do with the topology rather than the circuit being tube or transistor. If for example the tube circuit is fully differential in design, there will be no even ordered harmonics and so the circuit will have a more neutral presentation.

Conversely you can give transistor circuits a richer sound by building them single-ended- this will result in more of the lower-ordered harmonics.

Linearity of the devices themselves has a big effect on the sound of the circuit as well. The simple fact of the matter is triode vacuum tubes are the most linear form of amplification known. Additionally, it is easily demonstrated that even the most pedestrian tube amplifier will make less odd ordered harmonics than any transistor amplifier; a sine wave generator and an oscilloscope are all that's needed to demonstrate this.

This is why tubes are still around half a century after being declared obsolete.

"This is why tubes are still around half a century after being declared obsolete. "

Atmasphere, I often wonder what the SOTA is in tubes themselves these days?

Are NOS tubes still the SOTA or has tube production technology advanced at all since the heyday of tubes in general 40+ years ago?

I've noticed prices of new tubes seem to be going up. Is that negatively impacting the value proposition?

"Additionally, it is easily demonstrated that even the most pedestrian tube amplifier will make less odd ordered harmonics than any transistor amplifier; a sine wave generator and an oscilloscope are all that's needed to demonstrate this."

OK, if it is so easy, can you demonstrate that please? WHich amps specifically would you select to do that?

ALso remember demonstrating something does not prove it. Other demonstrations with different amps could have different results.

Even if true, does that mean any tube amp is better than any SS amp? I doubt that!

I like tubes in general as much as the next guy, but just trying to keep things in perspective and avoid people jumping to conclusions based on partial facts.

Mapman, the test is simple- put the amp on a speaker load (nearly any load will do) and run the amp up to clipping with the sine wave, and observe the results on a 'scope.

Of course others have already done that. Goto Google, click 'Images' then enter:

tube clipping characteristic

The first two images will show you the difference- the transistor characteristic being the first image. Note the squared-off waveform of the transistor test- as if someone cut off the tops and bottoms of the waveform with a knife. These sharp corners are evidence of odd ordered harmonics. This test is common to all transistor amps.

The tube amp has rounded corners- less odd-ordered and lower orders as well. This characteristic is common to all tube amps.

Now this test is at clipping but this difference between tubes and transistors has been quite well documented in the last 40 years and really isn't a topic of debate as it is so readily measured and heard. It is why nearly all guitar players use tube amp, BTW.

However, almost any audiophile will correctly argue that we don't listen to amplifiers at clipping. And I agree with you in your surmise in the second to last paragraph of your post. A cheap tube amp with lousy transformers and the like is still a crappy amp.

However, the fact of the odd-ordered harmonic distortion issue will not go away despite all this. All it says though that a transistor amplifier will sound harsh compared to a tube amp **generally speaking** (and with rare exception...).

A lot of people are OK with that, thinking that they can use a synergistic approach to deal with the harshness. But look back at my original post here- I specified the difference between sounding like *music* or sounding like a *good hifi*. Its that nuance, that nth degree, that I am talking about- not the ability to weld with the amp or the like.

YEs, I will chose to avoid clipping all together, thanks.

Easier to do with modern speakers these days with smaller and more efficient switching amp technology. These are game changers in the SS versus tube amp debate IMHO.

If my choice were limited to massive monster SS amp or tubes, I might chose the tubes as the lesser of two evils. Most likely I would go to high eff.speakers to avoid all the amp pain incurred with any large hot running, and heavy amp.

OF course some do not like the sound of switching amps they have heard either for whatever reason. Class A SS or bust! OR maybe tubes?

If you are going to clip, better off with a tube amp in general I would agree, though some SS amps claim soft clipping characteristics similar to tube amps though no the same.

I'm satisfied with the softening of the tube amp claim to accept that not all tube amps are inherently superior to any SS.

Tubes in the phono and line level devices is as far as I will go. What's involved to keep a tube power amp especially a large one running properly does not appeal to me personally, but may be the best solution for some.