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what makes amps sound so incredibly different? i dont mean tonally or equalization wise, that is fairly simple, but in terms of texture, what makes a mesa break up so starkly differently from a fender? or a vox from a marshall?
How do mesa's have such good preamp dirt, where on a fender, you have to really juice the tubes and speakers before you get that wonderful break up?

different gain structures, different driver tubes run off different voltages, different value coupling capacitors, etc., etc., - the list goes on and on - some folks like to run their preamp tubes on 240v, and others prefer 340v (or higher with MESA!).
Of course different output tubes will sound, -------- well, different too
Great sounding amplifiers are the result of many hours of intensive listening and tweaking - by the way, Leo Fender had a good ear for a clear sound and gradually improved the clarity of his amplifiers until the BEATLES and the STONES came along and showed him how grungy EL84 based amps could also sound good, but in a totally different way.
Maybe you should have asked a simpler question, like - "how long is a piece of string?"
bajaman

A very likely reason two amps can sound different, yet measure similarly on the test bench, is that the measurements typically taken are not done under the real load an amplifier will encounter with a dynamic waveform. Secondly, I'm not sure the typical bench measurements are measuring the right things regarding how an amplifier will sound.

To simplify a lot, there are a certain number of gain stages, and filtering/attenuation at and between these gain stages.

The gradual distortion of a gain stage will vary, as bajaman said, with tube type, voltage, and how it is biased (the signal will "hit the wall" on one side or the other, or both at the same time).
You can find a lot of information about that here : http://www.valvewizard.co.uk/gainstage.html

How you filter and attenuate the signal between stages will have a big impact as well. That's why you can get interesting sounds with JFET emulations (e.g. replacing each 12AX7 gain stage with an adequately-biased J201, a 9V power supply, and keep all the rest identical).

TragicTravisty wrote: ↑08 Dec 2008, 01:35 what makes amps sound so incredibly different? what makes a mesa break up so starkly differently from a fender?

Simple answer, Extra gain stages. (as mentioned)

It's a common Q, What's the "main" difference between Marshall and Fender amps?
I would Answer, Power Valves first.
Just reading the data of the 4 most common Power Valves gives a clue.

From memory?
American
(both Tetrodes)
gm 6V6 =3,800
6L6 =8,000

British
(both Pentodes)
gm EL84 =11,200
EL34 =11,200

The data will show that "gm" (Transconductance) is way higher in EL34/84.
If you don't know what that means,, just think of it as GAIN.
You only need about a 30Volt signal at the input of those pentodes to get them at full output.
Whereas tetrodes need about 70Volt swing.

You often read the term British or American sound when reading Amp reviews,,, well now you know why.
For details,Read page 7-8 on the Valve Wizard link above that *JiM* has kindly linked to, for an explanation of Transconductance.

If one was to swap a 6V6 for EL84 in the same circuit, the EL84 would distort long before 6V6.
When it comes to most modern Amp circuits they often have many extra gain stages which adds even more sensitivity and those designs rely more on preamp distortion rather than Power stage OD effect. With master volumes it's more likely preamp distorting long before power Valves.
A lot of magic can also be found in the way power supply voltages are derived.
To generalize;
Power supply, Valves used, Output Tx, circuit topography.
And the piece of string grows ever longer.

BTW The Valve wizard book is well worth reading if you want to know more.
Phil.

You could compare circuit diagrams of, say, those Mesa and Fender amps and see plenty of differences in them. Those differences are largely the answer to your questions of "what" and "how".