For non master volume amps... how does it work?

[Pierre]

Basically, with a gain + master volume amp you control the preamp volume (i.e gain) and the power amp volume (loudness).
But without a master volume, how does it work?
Are the preamps on these designed to stay clean (which I highly doubt)?
Does the distortion start to happen on the preamp and then the poweramp when it's cranked?
Usually at what point do you get full preamp saturation for instance?

just curious about this...

[joelap]

Re: For non master volume amps... how does it work?

I'm going to attempt an explanation of this to see how much of an understanding of it I do. If I'm wrong, i'll delete the post when someone chimes in so dont take my word for it yet!

Ok. With a post-phase inveter master volume amp, the gain is the preamp volume. Basically controlling the output volume of the first gain stage (like on a Vox AC30). The master volume acts as a volume control after the phase inverter has already done it's job. The difference between the two is that the gain or preamp volume is actually controlling how much to amplify the signal, while a PPIMV controls how much of the already amplified signal to shunt to ground, and the rest gets sent to the power tubes.

A non-master volume amp basically doesn't have the volume controlling the already amplified signal. The only volume control on the amp would be the one coming out of the first gain stage. In that respect, the power tubes are always cranking out what you dial in, whereas with a PPIMV you can crank that preamp and chill the poweramp out for breakup. Generally speaking, non-master volume amps are characterized by power tube distortion, since by the time you get the preamp to distort enough, you better be wearing ear protection!

The problem I have with non-master volume amps is that when you want to play below 3 on the volume knob, the tone sucks since the signal is barely being amplified. On the sound city I used to own, anything below three on the volume and you were wasting your time. HOWEVER, turn it up past three and get the tubes cooking and it was heaven in a tolexed box. that's why the Vox AC30 I'm builind now is getting a PPIMV control.

To answer your other questions: I dont know if the preamp is designed to stay clean. Maybe on some amps, but on others like the Marshall JTMs I cant imagine so. I found the distortion on my sound city to start with a little poweramp "spanky" kind of sound, then as you turned it up the preamp and poweramp would start to crunch almost simultaneously. I found full poweramp distortion to be around 7.5 with my sound city, from there the rest on the volume knob seemed to add only a little bit of preamp gain (I may be wrong about that though). At 7/7.5 on the amp volume, I was able to roll back my guitar volume for decent cleans, after that forget it it was crunchy no matter what.

Hope I actually made sense.

[bungalowbill]

Re: For non master volume amps... how does it work?

Once you get to a certain point on the volume (say 5 or 6) the amp will start to "break up". It won't really get all that much louder but it will start overdriving the power tubes and the phase inverter tube. The overdriven sound that you get this way is usually very complex and natural sounding and to quote Lew not "the angry bag of bees tone".

[Pierre]

Re: For non master volume amps... how does it work?

YES! Ok now I totally understand hehe...
So if you want to simulate a non master volume amp with a master volume one, you put the master at 10, and control the gain as the overall volume. Right? Not that anyone would do that, but that's what a non master volume amp seems to do Thanks dude!

[joelap]

Re: For non master volume amps... how does it work?

^ Exactly.