hi...many amps have "master volume" knobs on them...what are their mission exactly?...is it some kind of attenuation?...if so is it possible to saturate tubes at low volume levels without getting attenuaters? (i think we can't by the way :) )
It depends on the amp. It could be the volume of the poweramp, which means setting it low will result in just lower volume with ss amps and less tube saturation in tube amps. But for example in the Vox Valvetronix series the master volume decides how much of the signal goes through the Valvetronix tube circuitry and the actual poweramp is controlled using the wattage selector switch. In short: the effects vary per amp.
Attenuating an amp with a volume switch doesn't work: you need to 'drive' the tubes and the only way of reducing the volume is by reducing the energy going from the tubes to the cab. A simple know won't work, you'll need a mechanism to get rid of the energy and transform it into something else then movement of the speakers. Usually this is done by transforming part of the energy into heat.
Note that attenuating will have a noticable effect on the sound. It's usually better to mic a tiny tube amp instead of attenuating a big 100W tube amp. Attenuating is really a last-resort kinda thing, you'd better try getting an isolation box or smaller amp first.
thx for the useful info Arjen..i got the point
