preamp vs power amp distortion/drive

  • Thread starter Thread starter nate_dennis
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nate_dennis

nate_dennis

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I have read different accounts of "better." I'm not concerned with "better." I'm about to buy my first tube amp (a blues junior from a board member here.) I'm curious about acheiving power amp distortion. Would you simply back off the preamp and crank the "master?" Or is there something I'm missing? Thank you for your help (as always.)
 
Well, poweramp distortion is a question of really driving the poweramp section. To do this, you need to have the master running pretty hard, but you also need to be hitting it with a hot enough signal that the poweramp will be pushed into distortion.

So, I guess just to get a feel for it, set the preamp (with the poweramp low) for a pretty clean tone - I haven't played a Blues Jr in forever so I can't really suggest exact settings, but start around halfway and go from there - but not absolutely pristine just so you know there's a bit of juice running through it, and then start turning up the poweramp. Just do some Stones-y riffing, pretty chordal stuff, and dig in a bit. Keep turning it up until you start hearing the amp distort - what you're now hearing (since the preamp gain is unchanged) is the sound of a poweramp breaking up.

Also worth noting - you can certainly run a distorted preamp signal into a distorted poweramp, and as the Blues Jr (I almost abbreviated that BJ, then caught myself :p) isn't super-high gain, this might sound pretty good. Experiment, though.

Also, it'll be LOUD. Even, what, 15 watts of all tube amplification is pretty damned powerful.
 
yeah .... be aware of that.
(I'm the guy selling the Blues Jr.)
I've played gigs with drumbers using this amp.
Yes, it couldn't quite keep up with a loud drumber but it could keep up with a moderate one which means that it's loud.

Just turning the master up doesn't induce power tube distortion ...... the power tubes have to be putting out near their max to get into that zone which means fairly loud for only 15 watts.
The amp does take pedals pretty well, I like my Fulldrive 2 into it quite a bit.
 
Well fuckfiddles and shitsticks :)

You know you don't want that awful amp, Nate. If you buy that amp, gremlins will crawl out of your toilet and attach to your rectum. Everything you eat will taste like cigarette butts and rag water.

Plus those amps are made of wet paper towels and dog turds. They smell when they get hot, they attract flies, and rumor has it that street gangs are making initiates find people who own Blues Jr. amps and then they shove red-hot EL-84s in the owners' pee holes.

I'd hate to see any of these bad things happen to you. I have a special containment area where I could store the amp at my house. PM me for shipping info.
 
Tadpui said:
Well fuckfiddles and shitsticks :)

You know you don't want that awful amp, Nate. If you buy that amp, gremlins will crawl out of your toilet and attach to your rectum. Everything you eat will taste like cigarette butts and rag water.

Plus those amps are made of wet paper towels and dog turds. They smell when they get hot, they attract flies, and rumor has it that street gangs are making initiates find people who own Blues Jr. amps and then they shove red-hot EL-84s in the owners' pee holes.

I'd hate to see any of these bad things happen to you. I have a special containment area where I could store the amp at my house. PM me for shipping info.
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nate_dennis said:
I have read different accounts of "better." I'm not concerned with "better." I'm about to buy my first tube amp (a blues junior from a board member here.) I'm curious about acheiving power amp distortion. Would you simply back off the preamp and crank the "master?" Or is there something I'm missing? Thank you for your help (as always.)
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If you want just power amp distortion, start with the master down and turn up the preamp until it just begins to crunch, then crank the power amp all the way up. Yes, it will be loud. That's what you want, innit? :D
 
Why are you looking at it academically?

You turn the knobs until it sounds good.

What the fu ck is power amp distortion anyway? Why would you be trying to acheive a sound based on its description rather than how much it hurts your back teeth?
 
cephus said:
Why are you looking at it academically?

You turn the knobs until it sounds good.

What the fu ck is power amp distortion anyway? Why would you be trying to acheive a sound based on its description rather than how much it hurts your back teeth?
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LOL!!! I'm asking because I don't have the amp yet. I like to know as much about things as I can before I have them. I can't wait to turn the knobs until it sounds good, but until then I'm going to try to learn the most I can about it.
 
Hi there.

I purchased a Blues Jr about 4 months ago, have been experimenting with it *alot* to see what the deal is.

Yep, as mentioned, it's going to be LOUD. I've got test recordings of the amp mices with a '57 at various Master/Vol levels and worked my way up to almost maximum vol. You can hear the thing 3 or 4 houses away i'm sure.

I was also trying to hear the difference in sound when the power stage distorted. To my ears (of which there's not a lot of hearing left!) it's a subtle difference compared to the preamp distortion.

I kinda agree with cephus when he said just turn it up till it sounds good. From my testing, the sound got a a bit special when the master was up past at least 6 (or there abouts), reguardless of whether the preamp was max overdrivin, or only just breaking up.

Hope this helps.

I'm investigating iso cabinets or baffles to quiet the thing down. .. but think that the end sound is worth going to this trouble for.

Cheers,
FM
 
If you want to really hear how your power tubes sound, plug yr guitar into the power amp in/fx return jack. You'll lose control of the master volume, but you can at least check out how different the tubes sound.
 
starbuck26 said:
If you want to really hear how your power tubes sound, plug yr guitar into the power amp in/fx return jack. You'll lose control of the master volume, but you can at least check out how different the tubes sound.
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nah that won't do it because a guitar signal isn't gonna drive a power amp into distortion.
 
ocnor said:
It's a blues jr.. nobody has that much free time.
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Eh, I always thought it was a pretty cool amp for the price. A Blues Jr and an Ibanez RG520 (mahogany, H-H) gave some pretty kickass Santana-y lead sounds at a very reasonable volume.
 
Well, now it has a name I guess. I have an old classic 20. I keep the master up all the way and then turn up the pre gain till it just starts to get ornery. All this time, I was just calling it "personality".
 
starbuck26 said:
If you put an overdrive pedal in front of it it will. Try it.
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ONLY if you turn it up loud enough.
Power tube distortion mainly occurs when the tubes are close to producing up around their rated output.
Any distortion you hear before that point is only coming from the pedal.
To make the power tubes distort in that Blues Jr. you have to have them putting out the whole 15 watts and that's pretty loud.
Without using something like that Weber Mass, you have to have an amp up about as loud as it goes to get the power tubes into their distorted range.
 
This has been a nice thread.

I plus one on the observation that the magik happens on power tubes a little after halfway on volume.

Depends on taste though, a lot of my metalhead friends don't like spongyness of that, and favor the 100w amps for the tightness...
 
The easiest way to hear power amp distortion is to play an amp that doesn't have a master volume at all. And, IMHO, this will sound BETTER as well.

Crap, did I say that out loud? :)

Just kidding Nate. Seriously though, there are some really great-sounding non-master amps out there on the cheap*. (If it's already a done deal, though, I don't want to mess with that.)

*Especially if you're willing to build your own, which is really not that hard to do! :)
 
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