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Non ADA Gear => Amps => Topic started by: Soloist on April 13, 2017, 05:48:24 PM

Title: Power Amp volume
Post by: Soloist on April 13, 2017, 05:48:24 PM
I was wondering if anyone here runs their power amp wide open? I used to for some power amp distortion, but more and more I find myself running my MT200 in the 1:00 position and adding more preamp volume at the mixer. Who prefers what and why?
Title: Re: Power Amp volume
Post by: rnolan on April 13, 2017, 07:58:53 PM
Good question.  In a PA context I always turn the power amps full up so there's maximum headroom.
For my guitar rig(s) I tend to run the poweramp (B200s) at around 1 to 3 o'clock depending how loud I need to be.  From a gain structure and noise perspective, it's better to turn the preamp up so the amps input is being driven solidly and well above the input circuits noise floor, then use the output knobs to adjust for overall volume (as you have gravitated to).  I don't chase poweramp distortion, and it's probably not a great idea with transistor output stages eg B200s, MT200.  If you had an all tube poweramp you could but I prefer to shape all the tone and distortion in the preamp.
Title: Re: Power Amp volume
Post by: Dante on April 13, 2017, 09:30:51 PM
I run my preamps about 12:00 and use my power amps for volume. Each one is different, but neither is wide open. The MT-200 runs about 12:00 - 1:00 at gigs.
Title: Re: Power Amp volume
Post by: Kim on April 14, 2017, 10:23:47 AM
My Classic 60/60 is currently at 6 on each input volumes...if don't think I'll need it any higher than that.  :thumb-up:
Title: Re: Power Amp volume
Post by: Samuraipanda on April 14, 2017, 03:34:09 PM
I run my Mesa 295 full out but on the Class A 30W per side setting. I just adjust my volume with my effects unit.
When I use my MT100 I usually have the channels at about 12:00. Don't want to fry it running too high/hot.
Title: Re: Power Amp volume
Post by: Harley Hexxe on April 15, 2017, 01:52:43 AM
Hey Soloist,

    I used to try to run my MT200's at max, and control the levels with the preamp, but just as Richard said, it isn't a good idea with a solid state power amp. The noise from the MT200 is obnoxious, because it is basically a solid state power amp with tube characteristics injected into the signal path indirectly. The tubes never get the audio signal through them, and I believe this is where the noise comes from.
   I run them around 12:00 and use the preamp as hot as I dare, and that keeps the unwelcome noise down to a minimum. For this reason, I am leaning more toward a tube power amp in the future, to try to get more of the vintage type of interaction between the preamp and poweramp sections.
   With the B200S, I can dime those out, and there is still less noise than with the Microtubes.

   Harley 8)
Title: Re: Power Amp volume
Post by: Soloist on April 15, 2017, 07:22:47 AM
I don't run the MT200 wide open. My Mesa 50/50 is the only all tube power amp I have at the moment.  That's the one I was running wide open.  I guess I should have stated that in my original post.  :facepalm:
Title: Re: Power Amp volume
Post by: rnolan on April 20, 2017, 02:21:34 AM
Using power amps they way we do in our rigs, the best signal to noise & gain structure will be achieved from driving the amps inputs as hard as you can (for your loudest patch) without clipping them. And as Harley points out, turning poweramps up full generally introduces more noise so backing them off a bit makes sense. Whereas giving the amp a weak input signal introduces noise.

But some variables to consider (as depends on your particular rig):
What is driving the poweramp ? MP-1/2 ? Fx gadget after preamp ?, mixer ? so where are you adjusting the amps input signal level.
What do the vol knobs on the amp adjust ? (input ? output?) does it have vol knobs... etc
Have you got the gain structure of all your connected gadgets sorted ?
Title: Re: Power Amp volume
Post by: Soloist on April 20, 2017, 06:59:45 AM
I am currently re-doing my gain structures. So far my MP1 and Mp2 pre's are between 12 and 1 o'clock ourputs. On the mixer side each channel is at 10:00 and the mixer master volume is at 12:00. Fx units ins and outs adjusted to go as loud as they can before they start to clip. Power amp (using Mt200) is at the 1:00 position. It's loud but I wanted it a bit louder without having to mic my cabs. If I turn up the mixer it clips. >:(