Tube amp sweet spot vs. volume?

The Blues Jr. has 2 volume controls, 1 channel volume and 1 master. The master controls loudness and the channel controls "overdrive", so you can crank the channel volume to get the crunch, but turn the master volume down so you don't make your neighbors hate you.

Yes, you can substitute preamp overdrive (which isn't the same sound), or turn the volume down and forget it as I usually do, or you can buy or build an attenuator to crank up your amp and reduce the volume if you just have to have that cranked amp sound. Or you can buy or build a sensible amp with <1W power if you want to crank it around the house without an attenuator. Of course you can also permanently blow out your hearing, upset your neighbors and get the cops called by cranking your big amp.
:mrgreen:

The Blues Jr. has 2 volume controls, 1 channel volume and 1 master. The master controls loudness and the channel controls "overdrive", so you can crank the channel volume to get the crunch, but turn the master volume down so you don't make your neighbors hate you.

Interesting, so is the channel volume basically the pre-amp only and the master is the output? If so, aren't there tubes for both the pre-amp and output stages?

Just curious how that all comes together in the end: if your channel is cranked, and your master low, are you just driving your pre-amp tubes and not the output tubes?

Domo

Yes, yes, and yes.

Yea, I guess you are right. I never thought about it much, I just turn one knob to distort and the other to make it loud (and LOUD is the truth. I've never had it above 3.5 and that was playing with a drummer).

Last question :) (maybe..)

Since the tubes are the ticket to tone nirvana, are you only getting half the heaven if your not cranking the output tubes? Or is all, or most, of the tone shaping happening in the pre-amp?

And a related question, if BillyBoy doesn't mind my jumping on his thread: if an amp doesn't have separate gain and master controls, but only one volume knob, is that controlling the preamp, the power section, or both proportionally?

BillyBoy

The only REAL way to get power tube saturation is volume. Even an attenuator cuts the signal to the speaker which is part of the overdriven sound. So the solution is to get a lower wattage amp you can really crank. Neil Young is famous for cranking his 1950's Fender Deluxe 12 amp watt to max. And he plays to huge crowds. Of course the amp is mic'd into the PA, but you would be surprised how loud an amp like this is. Here he is with Pearl Jam, he has the little yellow combo amp behind him on the stage. You can still hear him.

http://www.youtube.com/watch?v=PTTsyk-pyd8

But you don't have to max a tube amp for it to sound great. If I get my Hot Rod Deluxe or Blues Jr. up over 4, they start to scream. Can't play 'em at home like that, but if you ever get out....

To answer Slej, I believe you are correct, on old one channel amps the volume was strictly pre-amp. So you had to really crank them to get distortion. Now with modern amps you can crank the preamp to get overdriven distortion, and then use Master volume to keep the volume down.

And I tell ya, I love cranking the Volume on my Blues Jr to max but keeping Master down. Sounds just like a big ol' Marshall. :twisted:

Thanks for all the replies.

It seems amps from small to big have master volumes. I guess the only question left is, if your limiting the output tubes with a master volume, that mean anything as far as tone?

Volume and gain knobs are the same thing, just at different parts of the amp. "Preamp" stages of the amp amplify voltage of the signal to drive a following part of the amp, and the "power" or output stage puts out power to drive the speaker(s).

With a single volume knob, the potentiometer is usually after the first "preamp" stage. It controls how much of the amplified signal from the first stage goes to the second. From there on, it's all fixed. The amp designer has tried to balance everything so that when the volume's cranked and the input signal's at the expected maximum level, every stage of the amp will more or less max out at the same time. (May not come close to doing that, but that's the ideal.) For a guitar amp, it may deliberately be imbalanced so the "preamp" stages go into clipping distortion before the power tubes or vice versa, depending on the sound the designer's trying to achieve. (And of course, overdriving it on the front end throws off the amp's designed balance and makes preamp distortion from early stages that normally wouldn't distort.)

With a master volume and gain knob, the gain is the volume control above, but the preamp's balanced so that when the knob's turned up the next stage of the preamp gets overdriven into distortion. The master volume's right ahead of the power stage so it controls how much of that overdriven, distorted preamp signal gets to the power tubes. And it's probably set up so that cranking it will push the power tubes into overdrive distortion as well.

Yes, output overdrive distortion sounds different from distortion that's just coming from the preamp. Doesn't mean either one's bad. They're just not the same.

BillyBoy

You can tell when you are pushing the power tubes into saturation, the sound comes very alive for lack of a better description. You start getting fantastic sustain. You also start getting noises like feedback, pops, crackles. That may sound bad, but it's not, at least for me. I love it when the amp starts sounding like it will explode. :twisted:

But if you are into Tom Scholtz's type tone, that is ALL preamp. That is not what tube saturation sounds like. I have posted this video many times, but it is an excellent example of power tube saturation. Listen carefully to the whole clip, some of the best is at the very end.

http://www.youtube.com/watch?v=Obfci1CIqq8

Listen to all the noises Neil's amp makes throughout the song, it feedbacks, pops, crackles, whistles. If you know how to control it, it is awesome. But it is nothing like modern distortions. It is better. You have to be there to appreciate it.

You can tell when you are pushing the power tubes into saturation, the sound comes very alive for lack of a better description.

Yes indeed, it becomes very open and 3-dimensional. I believe I've seen it described as power amp "bloom." And it's a beautiful thing!

With a single volume knob, the potentiometer is usually after the first "preamp" stage. It controls how much of the amplified signal from the first stage goes to the second. From there on, it's all fixed. The amp designer has tried to balance everything so that when the volume's cranked and the input signal's at the expected maximum level, every stage of the amp will more or less max out at the same time. (May not come close to doing that, but that's the ideal.) For a guitar amp, it may deliberately be imbalanced so the "preamp" stages go into clipping distortion before the power tubes or vice versa, depending on the sound the designer's trying to achieve. (And of course, overdriving it on the front end throws off the amp's designed balance and makes preamp distortion from early stages that normally wouldn't distort.)

Very interesting; thanks. 8)

Or you can buy or build a sensible amp with <1W power if you want to crank it around the house without an attenuator.

I have not found any around to buy for a reasonable price .. are there some? Or maybe some kits? I have not actually searched around for those.

That's kind of the problem with tube amps and why I haven't bought any since mine got stolen. Obviously people have their preferences, and a lot of people here will flame me for this, but my opinion is a good solid state amp sounds a lot better than a tube amp at low volume. I'm never anywhere where I can play at any volume even close to make a tube amp start to break up, even a small one, so I use solid state.