Valve Amp Wattage and Perceived Volume

Dave_Mc · October 2023

Yorkie said:

Barquentine said:

I've often played with a 50w combo turned up about half way. Does this mean I could have used a 5w combo turned all the way up?

Besides power, there’s also the speaker factor — most 5W combos I know have a 10” speaker.

Or even smaller...

To be fair, there are some 5 watters with 12" speakers. But you do have to look. And that also makes them a lot heavier and bigger...

ecc83 · October 2023

I would have thought by now that most 'seasoned' guitarists would know that the power output of an amplifier is only very loosely related to the rotation of the volume control?

The power output depends on the drive voltage to the grids of the output valves, that in turn depends upon the gain of the rest of the valves which ultimately depends on the output of the guitar!

ICBMs point about "headroom" is also important. That extra power for good dynamics is vital for a good sound. The type of OP stage matters as well. "5 watt" amps are almost all (but not quite!) single ended, class A(ish) cathode biased and 5W is all they have got. You can play a 100W fixed biased amp at an average of 5W but it will sound much better.

Dave.

Yorkie · October 2023

ecc83 said:

ICBMs point about "headroom" is also important. That extra power for good dynamics is vital for a good sound. The type of OP stage matters as well. "5 watt" amps are almost all (but not quite!) single ended, class A(ish) cathode biased and 5W is all they have got. You can play a 100W fixed biased amp at an average of 5W but it will sound much better.

There are some better examples out there, but the Marshall Class 5 runs out of clean headroom at about 11 o'clock. Barely loud enough for the neighbours to notice you’re playing, useless for playing with others.

ICBM · October 2023

Yorkie said:

There are some better examples out there, but the Marshall Class 5 runs out of clean headroom at about 11 o'clock. Barely loud enough for the neighbours to notice you’re playing, useless for playing with others.

Actually the Class 5 is a perfect example of a badly-designed low-power valve amp - too little headroom and too much compression to be workable with a band, but too loud for home use (unless you have no/very tolerant family). The later version with the low-power switch is maybe more useful, but it still sounds poor. Anyone familiar with proper Marshall circuits could look at the schematic and see why - it’s all backwards, the EQ is too soon in the signal path and then there’s too much gain after it.

They’re also badly-made, if it matters… flimsy and prone to rattling - only really useful as a nice-looking shell for a complete strip and rebuild - Rat Mods used to do that.

Sorry, just one of my pet amp hates

.

Yorkie · October 2023

ICBM said:

Actually the Class 5 is a perfect example of a badly-designed low-power valve amp

I'll see your Class 5 and raise you one Origin 5C.

Looks like a cab, useless low power mode, 8" speaker (and what a speaker), sounds even worse than the Class 5... Such a shocking achievement nearly ten years after the Class 5 was panned by everyone except maybe Joe Bonamassa and Rob Chapman.

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Valve Amp Wattage and Perceived Volume

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