[BillSPrestonEsq]

help lower the gain to allow power tube distortion? Realize, my goal is not death metal distortion here, but lite o/d.

Also I plan on using it clean a fair amount as well. (btw, I did one of the ground mods last night and it killed a huge amount of the inherent hum. Maybe 70% of the hum)

I put a groove tube in it and it sounds better all the way up. (Less like a hornets nest)

Like I said though, as little preamp distortion as possible with capacity to get some lite power tube drive would be my ideal.

Do I want 12 at7? 12 au7?

[jreid]

This depends really. If you don't have enough preamp gain, you will never get poweramp distortion. Lowering the gain in the preamp is not going to allow you to get poweramp distortion at lower volume levels. The poweramp needs a certain level of signal before it distorts.

Lowering the gain in the first stage of a preamp will allow a cleaner signal through to the poweramp. This would mean that more of the distortion will happen in the poweramp.

With the valve junior there is only one preamp tube so the gain the gain of that tube is what will drive the poweramp into distortion. Don't worry about the gain of that tube so much and concentrate on the sound of the tube. You may want to look at the speaker as well, as it will greatly affect the tone.

Regards
John

[tht00]

Originally Posted by jreid

This depends really. If you don't have enough preamp gain, you will never get poweramp distortion. Lowering the gain in the preamp is not going to allow you to get poweramp distortion at lower volume levels. The poweramp needs a certain level of signal before it distorts.

Lowering the gain in the first stage of a preamp will allow a cleaner signal through to the poweramp. This would mean that more of the distortion will happen in the poweramp.

With the valve junior there is only one preamp tube so the gain the gain of that tube is what will drive the poweramp into distortion. Don't worry about the gain of that tube so much and concentrate on the sound of the tube. You may want to look at the speaker as well, as it will greatly affect the tone.

Regards
John

+1

I have an old 5 watt Kalamazoo at home. It has one 12ax7 and one EL84. I was curious if I could get any preamp distortion by modding a master volume onto it. So, I took it appart, checked the power amps for voltage (I've found the (very old) power caps don't hold dangerous for more than a couple seconds. They need replaced- they are letting some hum through.). Anyways, I double checked my wiring, and powered up the amp. I adjusted the potentiometer down (Master volume) and the volume up (now could be called a 'gain' control), and really, I got absolutely no distortion.

I found that all of my distortion from that amp is coming from the poweramp. The 12ax7 isn't distorting, but it is allowing the poweramp to distort. By swapping out to a lower gain tube, you will essentially be 'turning down' your volume (among other tonal changes with the tube change, of course). Needless to say, I removed the 'Master volume' and returned everything the way it was.

[BillSPrestonEsq]

Originally Posted by jreid

This depends really. If you don't have enough preamp gain, you will never get poweramp distortion. Lowering the gain in the preamp is not going to allow you to get poweramp distortion at lower volume levels. The poweramp needs a certain level of signal before it distorts.

Lowering the gain in the first stage of a preamp will allow a cleaner signal through to the poweramp. This would mean that more of the distortion will happen in the poweramp.

With the valve junior there is only one preamp tube so the gain the gain of that tube is what will drive the poweramp into distortion. Don't worry about the gain of that tube so much and concentrate on the sound of the tube. You may want to look at the speaker as well, as it will greatly affect the tone.

Regards
John

The gain down would be good. Id rather have a low poweramp distortion to play with. The speaker sounds pretty good for an 8.

[Major Tom]

+1

That's not going to have a lot of preamp gain; you can, I think, accomplish pretty much the same as a lower gain tube by cutting the signal level a bit in front of the amp. I don't think a modest signal would drive that pre amp into distortion.

[BillSPrestonEsq]

Originally Posted by Major Tom

+1

That's not going to have a lot of preamp gain; you can, I think, accomplish pretty much the same as a lower gain tube by cutting the signal level a bit in front of the amp. I don't think a modest signal would drive that pre amp into distortion.

yeah, its with the emgs mostly. I think it is preamp, because swapping the sovtec made a HUGE difference. I might need to swap out the power tube as it might just be buzzy sounding.

[BillSPrestonEsq]

I tried it, and for my planned purpose... I think it will work well. I still need to try a few more tube swaps, but I needed the channel to break up later.