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AUDIO FORUMS >> General Discussion and Support >> Will a Tube amp driven below distortion sound SS?
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Message started by flargosa on 12/04/15 at 17:43:34

Title: Will a Tube amp driven below distortion sound SS?
Post by flargosa on 12/04/15 at 17:43:34

From what I have read the difference between Tube and SS amps is how it distorts when driven to its limits. The distortion is what gives it a tube or SS sound signature.

If the amp is never driven to its limits say only 1 - 2 watts in a 6 watt amp, so there is zero distortion. Will the tube and SS sound similar since there is no even or odd harmonic distortions?

Title: Re: Will a Tube amp driven below distortion sound SS?
Post by Steve Deckert on 12/05/15 at 02:43:59

That's a great question! The short answer is no. Regarding distortion there is no question you could easily tell a tube amp from a solid state when both are turned up to clipping, but lets assume we're at normal playback levels and there is no distortion from either amplifier. The difference between tubes and solid state are the number of stages of gain needed to get the job done combined with the size of the coupling capacitors. In a tube amp the coupling capacitors between each stage are on average 100 times smaller and operate at between 10 and 30 times the voltage. The smaller the size of cap the less distortions it will have and the more transparent it will be. The same is true for voltage, the higher the voltage capacitor the less distortions and better transparency. What is often overlooked is the rather huge difference in speed between the large caps vs. the small. Speed equals resolution. Then there is instantaneous peek power which can be and usually is higher than solid state giving you a more believable sense of dynamics. And the holy grail of tube amp designs usually requires and has no negative feedback. Solid state on the other hand typically can not be made without lots of negative feedback. In solid state it takes many more output devices to get the same power as a tube so in the end, it's a less is more thing... less parts, more transparency.

From that point, the differences are magnified by the output transformer which only the tube amp has. The transformer blocks the back electromagnetic field created from the voice coil in your loudspeakers. You can think of this field as a voltage moving backwards through the cable into the output device It's kind of like hooking two amplifiers up to each other and turning one up loud and the other down soft and then let them fight it out. This battle between the back EMF and the output signal of the amplifier is what causes ruler flat response on paper to measure all over the map in real life application. Conveniently on paper amps are always measured into a purely restive load even though they will never see such a thing in their lifetime. So you see, the perfect specs of Solid State are far less perfect in reality. Unlike the output transistors in a solid state amplifier which are directly connected to the loudspeaker, the vacuum tube is protected by the output transformer and as a result the amplifiers response is largely unaffected by the back EMF from the loudspeaker so it of course is going to sound better.

Steve

Title: Re: Will a Tube amp driven below distortion sound SS?
Post by Archie on 12/05/15 at 18:12:05

Wow, what a great explaination! I'll be cutting and pasting this to send to a few doubters that I know. :)

Title: Re: Will a Tube amp driven below distortion sound SS?
Post by flargosa on 12/06/15 at 05:20:08

thanks for the detailed reply. :)