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Is there any difference in clean tone sound between a valve/tube amp and a solid state amp? i.e., does having a valve in an amp affect the clean channel, or only the distorted channel?

Apologies for the newbie question, but I was just wondering if there is any advantage (or disadvantage) to having a valve amp if you are using the clean tone.

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up vote 15 down vote accepted

"Clean" tone is a relative term, especially when talking about tubes.

Nearly all amplification circuits introduce artifacts into the waveform; what you put in is not 100% exactly the same as what you get out. Most solid-state circuitry can achieve a waveform that is 99.5% "similar" or better; that is, they achieve less than .5% total harmonic distortion or THD. Some can achieve <.01%. This is, in the technical sense, a "clean tone", where output == more input, and this is generally preferable for most professional audio amplification needs. However, it can result in a disagreeable tone for an electric guitar (and other instruments); too much highs, too much mids, too "angular" a tone, etc.

Tube amps have a markedly higher THD; the circuit doesn't respond to the waveform as fast, and the ratio of peak input to peak output in the waveform diminishes earlier, but more gradually, than solid-state. In layman's terms, tubes "distort" the wave more than solid state at all signal levels, "coloring" the tone of the instrument, and they "clip" at lower levels than SS. But, tubes have a softer "peak" level than SS circuitry. which will simply "chop off" the waveform at the maximum gain level. Tubes instead "squish" the parts of the wave that exceed the max gain.

So, your answer is, at low signal levels that both circuit types can produce without clipping, there will be a slightly different tone produced by the tube amp, but unless you are comparing two amps side by side you would not detect the difference (and amps of all types will produce tonal variances regardless of tubes vs SS). At higher signal levels, the SS amp will still have "headroom" while the tube amp starts to "squish" the waveform peaks. In this grey area between clean and overdriven tone, you'll get a lot of different behaviors between SS and tube and between various circuit designs. Obviously, at "true" clipping levels, SS will produce a markedly different waveform than tube and the difference is quite noticeable until you push both amps into an extremely square wave.

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Great technical explanation. Thanks! – Jduv Jul 14 '11 at 14:37
It is not really possible to push a tube power amp "into an extremely square wave" anyway. – leftaroundabout Jul 17 '11 at 0:36

As a studio engineer friend once told me "I can clean every bit of feeling right out of this music". He was referring to modern solid state and digital techniques. The other posts talk about the mechanical details of the signal. Maybe I pinpoint the visual as I have been experiencing a "dirty" VOX tube sound that I am trying to clean up. The tube response is much smoother and mellower and because of that gives a "warmer" or fuller tone. I'm trying to change tubes to get a crisper sound on the pre-amp side and add "head" room on the power side. The sharper pre-amp signal sent to a power tube with more headroom will allow for a cleaner tone at more volume before the sound distorts (or crunches). I'm plying through a 4 watt amp at practice volumes. The solution for performance is a more powerful amp that you can drive at the proper level to get the sound you want. Example Carlos Santana medium drive on his amp to the edge of crunch- AC\DC Angus Young playing in the crunch zone.

Hope this helps...

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Turning up the master volume on a valve amp overloads the amps power-amp section which typically adds a musical compression and slight distortion to the sound while still being 'clean'. This aspect that also affects the perceived 'feel' of the amp, which is what people talk about when they talk about a spongy valve tone.

The power-amp section of a solid state amp (at least ones that don't use digital modelling to emulate valves) typically are designed not to distort the sound at all (as when they do it doesn't sound musical as it does with valves) and as such they tend to have a 'clear' or 'clinical' clean sound. This is not necessarily a bad thing, the Roland Jazz Chorus for example is a very popular solid state amp

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Have a look at this question - I think that although full solid state amps are slowly getting better at emulating Valve aps, there is a definite something about a Valve amp that works well with guitar, whereas a solid state amp is generally more clinical.

More obviously, when cranking up the drive/input gain, a Valve amp tends to produce a warmer fuzz/distortion than a solid state one. This goes for the clean channel as well as the overdrive channel.

All a matter of preference of course, but definitely distinct differences.

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Thanks - I've just bought a new valve amp and there is a difference in tone between that and my old (solid state) amp. I just wondered whether that was because my old amp was a cheap one though! It does seem there is something about valve amps though. – Phill Sacre Jul 13 '11 at 10:07
Though this question is voted up, I don't think it relates to the question; it refers to the behavior of a valve vs a solid-state transistor when clipping, while the question specifically asked about clean tone. – KeithS Jul 13 '11 at 18:30
@KeithS - no. Although in my second paragraph I mention what happens when drive is increased, my entire answer is about the clean channel, not the distorted channel. – Dr Mayhem Jul 13 '11 at 20:51

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