This is really stupid...

AudioAUnderdog · 09-03-2009, 03:52 PM

I've had my Peavey Classic 30 for about two and half years. I bought it used, and I knew there had been modifications made to it. For those two and a half years I'd turn it all the way up on the dirty channel and it would sound almost as clean as the clean channel. Where was all that tube break up everyone talked about?

Well that last thread about the Classic 30s got me thinking. Why wouldn't mine break up? Was there something wrong with it? Did I need to change the tubes? Then I made a discovery last week. There's a little knob I hadn't noticed before on the back of my amp (on the inside) and it didn't look stock. So I turned my amp on and turned the knob... And there was the break up! My amp had an attenuator that I had forgotten about. The person who sold it to me mentioned it, but at the time I didn't know what an attenuator was.

So now I realize that for those two years I didn't even need my Jekyll and Hyde or my RAT. I could have just brought the footswitch for the amp.

I do have one question though. It sounds really muddy and bassy, is this just the way Classic 30s are? When I turn the treble up and the bass and mids down it sounds great. Maybe I'm just used to my Fender.

**jamforchrist123** · 09-03-2009, 03:57 PM

I don't really have a response to your question, but that gave me a good giggle. Glad you finally figured it out!

***BillSPrestonEsq*** · 09-03-2009, 04:12 PM

Quote:

Originally Posted by AudioAUnderdog

I've had my Peavey Classic 30 for about two and half years. I bought it used, and I knew there had been modifications made to it. For those two and a half years I'd turn it all the way up on the dirty channel and it would sound almost as clean as the clean channel. Where was all that tube break up everyone talked about?

Well that last thread about the Classic 30s got me thinking. Why wouldn't mine break up? Was there something wrong with it? Did I need to change the tubes? Then I made a discovery last week. There's a little knob I hadn't noticed before on the back of my amp (on the inside) and it didn't look stock. So I turned my amp on and turned the knob... And there was the break up! My amp had an attenuator that I had forgotten about. The person who sold it to me mentioned it, but at the time I didn't know what an attenuator was.

So now I realize that for those two years I didn't even need my Jekyll and Hyde or my RAT. I could have just brought the footswitch for the amp.

I do have one question though. It sounds really muddy and bassy, is this just the way Classic 30s are? When I turn the treble up and the bass and mids down it sounds great. Maybe I'm just used to my Fender.

Are you sure thats an attenuator? to me it sounds not like an attenuator much, unless I am miassing something.

AudioAUnderdog · 09-03-2009, 04:54 PM

I thought an attenuator was something that made tube amps get good sounding break up and low volumes, which is what this thing does. When I turn it the other direction it gives me tons of head room, and hardly any break up at high volumes. Maybe it's something else, I don't know much about amp mods (obviously lol).

***BillSPrestonEsq*** · 09-03-2009, 04:58 PM

Quote:

Originally Posted by AudioAUnderdog

I thought an attenuator was something that made tube amps get good sounding break up and low volumes, which is what this thing does. When I turn it the other direction it gives me tons of head room, and hardly any break up at high volumes. Maybe it's something else, I don't know much about amp mods (obviously lol).

Basically an attenuator converts output to other forms of energy, allowing you to push the amp at lower spl.

However, the amount of breakup at various points on the knob should be roughly constant, (other than speaker saturation.) The volume should go up and down essentially.

**thesteve** · 09-03-2009, 05:01 PM

What you're describing sounds more like a master volume knob than an attenuator. With an attenuator in place you should (theoretically) be getting roughly the same tone regardless of volume. Turning the attenuator one direction will make it quieter, while turning it the other direction will make it louder, but the tone shouldn't change much.

AudioAUnderdog · 09-03-2009, 11:58 PM

So what exactly is the purpose of a master volume knob?

**Rainer.** · 09-04-2009, 12:05 AM

Master volume controls the volume of the signal hitting the power amp, i.e. between the preamp and power amp.

An attenuator goes between the power amp and the speakers. It depends on what you want to overdrive, preamp, power amp, speakers, etc.

Ax · 09-04-2009, 12:16 AM

What it sounds like is the main knob on his amp has been replaced to control an attenuator and the MVC moved to the back.

**thesteve** · 09-04-2009, 12:45 AM

Quote:

Originally Posted by Ax

What it sounds like is the main knob on his amp has been replaced to control an attenuator and the MVC moved to the back.

Hmm...maybe...

Without seeing what does what exactly (whether pictures or otherwise) I'm just having trouble visualizing what could possibly be going on.

AudioAUnderdog · 09-04-2009, 01:17 AM

Quote:

Originally Posted by Dread Pirate Roberts

Master volume controls the volume of the signal hitting the power amp, i.e. between the preamp and power amp.

An attenuator goes between the power amp and the speakers. It depends on what you want to overdrive, preamp, power amp, speakers, etc.

That makes sense, it must be a master volume then.

If pictures will help then I'll take some over the weekend and post them.

**thesteve** · 09-04-2009, 02:45 AM

If you can tell how the knob on the back is hooked up to the amp, it could also lend some information on what exactly it is. If it's plugged into the effects loop, then it is a second master volume. If it's plugged in between the amplifier and the speaker, then it is an attenuator.

***BillSPrestonEsq*** · 09-04-2009, 09:53 AM

Quote:

Originally Posted by thesteve

If you can tell how the knob on the back is hooked up to the amp, it could also lend some information on what exactly it is. If it's plugged into the effects loop, then it is a second master volume. If it's plugged in between the amplifier and the speaker, then it is an attenuator.

and since this classic 30 seemed to be all clean headroom, it might be some other form of volume control at a different gain stage in the preamp. I am thinking that because even if it were a master volume or attenuator, this sucker should have broken up earlier. The only way to totally prevent that is to prevent the preamp from distorting, which seems like it would need to be early in the chain.