Power Stage Distortion Questions/Concerns

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Hello guys.

I understand that the ideal tone is through pushing tube amps into power-stage distortion.

I think I know what this means.

Tell me if I am acheiving this with my constant setup:

I use my Crate VC30 all tube amp (4 pre tubes; 4 power tubes) and turn BOTH the clean and gain channels volume up maximum.

I set the EQ to taste. On the gain channel, I set the gain knob to halfway.

I then control the volume/distortion/tone through my guitar's volume knobs and my playing touch.

The way I see it, I am inducing power-stage distortion by having the volume on both channels up maximum. Or maybe I am not and to really acheive this the guitar volume knobs must be at max???

By doing this am I burning out my tubes faster???

I love the control I get when I play this way and this is the only way I know.

[ux4484]

If you've been playing that way for a while and you haven't done any damage, it's unlikely you will by continuing to do so... maybe you'll shorten your tubes life...but unless you're doing a Pete Townsend on your crate I doubt you'll be swapping valves that often. I've always been of the 'If it sounds good, do it' camp on amp settings (as long as your family and neighbors can live with it).

....but, while I know what you are aiming for, I've usually been able to achieve that kind sound by just cranking the gain up high and not the main volume, but for that 'icepick in the forehead' tone, having them both cranked does the trick.

Anything that lets you get the range/sound you want with just using the guitars controls is a good thing.

[JohnH]

Id say that if you are getting the sound you like with the way you are running the amp, then its all fine. But I think that true power stage distortion only comes by running the output tubes hard, which fundamentally means that they are loud. If you are getting your tone at less than loud, then it is created in the preamp or earlier. The power stage does not know if it is getting a large signal due to preamp gain or due to the guitar output level. The tone could be very different however.

Some amps (such as my DSL401) have a master volume after the first part of the power stage, which is the phase inverter tube. This allows the PI tube to be driven hard and then the level reduced after that, giving some of the power stage distortion character, but at lower volume. Its not really power tube distortion however since the power tubes are not running hard . The other approach is to use an attenuator after the amp, between amp and speakers. This allows the power tubes to be pushed, but only a part of the output to go to speakers.

I don’t think it matters too much how you drive your sound. My understanding is that tubes are tolerant of being overdriven, perhaps using up a bit of life if you push the power tubes hard – but not a real problem.

John