I’m confused by the term distortion. Why do people look for distortion in tubes? The word distortion was always negative to me. I don’t even know if I used correct terminology for my question.


This may address. Some say the audiophile quest is finding and determining the setup that yields the right amount of distortion, if any, to their ear.



Distortion, in an amplifying device, is any change between the input signal and the output other than magnitude. If operating at unity-gain, then it would be any difference between the input or output, period.

An amplifying device could be a single transistor or tube (appropriately employed), a complete circuit or the overall “amplifier”.

All amplifiers do three things:

  • Increase the magnitude of the incoming signal
  • Add noise
  • Add distortion

It is not, currently, possible to build an amplifier (or any other audio component) that does not add noise and distortion. It is possible to build an amplifier in which noise and distortion are below audible levels.

Thus, at any point where you’re choosing an amplifier based on its “sound” you are, by definition, making your choice based on the noise and distortion that it imparts on the output signal* vs. what it is actually fed.

Whether that’s a choice about the overall amplifier unit itself, the tubes you choose to run in it (or the op-amps or transistors … though those are less frequently user-accessible), you’re making a choice about what distortion(s) you will be subject to.

It’s worth noting that it isn’t difficult to measure these distortions. They tend, though don’t have, to be larger in tube-based amplifiers. The distortion and noise characteristics of different tubes, even of the same type, is also measurable.

I should also add … that any time someone is talking about “color” in an amplifier (or other component) be it tube or otherwise, it’s just a fancy name for “distortion”.

Distortion is only a negative if you don’t want it. There are multiple situations in music production where it is actively employed and applied (gating, compressors, effects pedals, phasing, EQ and saturation to name a few).

*Assuming that a) those distortions are audible in the first place and b) you personally are actually able to hear them.


In one word: it’s the accompanying harmonics to the fundamental tone.

To put in a context. One is playing a 500Hz tone but with his golden ears (or analyzer) is also seeing/hearing 1kHz, 1.5kHz, 2kHz, …, tones as well. This is distortion.

Distortion is a bad word. Use the euphemistic version instead. E.g.: “My tubes are giving that extra 2nd/3rd harmonics and I can feel my dopamine levels increasing”. :grin:

Note that tubes are giving those harmonics across the whole spectrum, since music is not about single tones. E.g.: 20Hz - 20kHz (more or less). What is the spectrum window that make it pleasurable for us, that’s the question that needs to be answered. Not to mention these harmonics also stack up with other tones, etc…

Cheers. :beers:

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Those are examples of a specific type of distortion … harmonic distortion.

There are other types of distortion.

All effect the measurements and the sound.


Right. I was being too minimalist since OP referred to tubes.

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Nelson Pass has some articles on the First Watt website.
They are in interesting read if your interested in what an Amp designer looks at in various measurements.

Though it does generally carry a negative connotation. It’s not always bad …



In following some of the comments in this thread, one must distinguish between distortion used for production versus playback. All of rock-n-roll is based on distortion, with some genres defined by a particular form. This includes electric blues, psychedelic and acid rock, punk and new wave, metal sub-genres, shoegaze, and (obviously) noise rock. Many artists defined their sound through a particular distortion effect pedal or set of effects pedals. Jimi Hendrix, Eddie Van Halen. An electric guitar can sound rather plain without distortion and effects. Tiny, tiny sounds are twisted into all kinds of unexpected and complex outputs via cascading layers of distortion and effects. Learn to play electric guitar and your respect for the skill required in the rock genre may decline. Mine did, but I still enjoy it.

Most of the replies and audiophile discussions refer to distortion in playback. Audio measurement fans often portray distortion as a negative, and sometimes it is negative. But at times it pairs well with specific equipment. We can all learn this through direct experience. Per the need to recognize original sources, playback involves relatively minor levels of distortion versus what is common in production. A thick “tube tone” or Audio GD amp distorts as heavily as practical, and more than many people want.


Perhaps because the right kind and amount are pleasing to the ear and can impart their own ‘personalities’. Some view that as a negative, some as a positive - I feel it’s good either way; whatever sounds best to you!