What to do with a 12AT7

[Whoopysnorp]

I have this JAN/Philips 12AT7 with very low hours on it lying around, and tonight I decided to put it in V1 of my JTM module to see if it got me more clean headroom. I didn't really notice much difference, so I decided to try it in the preamp stage on my RM100, since I never come close to using all the gain available on my MTS modules (right now a JTM, Blackface, SL+, and Grail, though I have a Voxless and modded XTC on the way from Jaded Faith). It sounded nice, but in the end I decided that it took away from the aggressiveness of the Grail, even with the gain on the module cranked up to compensate, so I went back to a Tung-sol 12AX7 in the RM100. Can anybody think of a good application for a pretty nice 12AT7 in an MTS rig, or indeed any guitar amp? I also have an Egnater Tweaker and Boogie Studio .22 in my apartment, plus a Rivera M100 and a Boogie Mark III in my rehearsal space.

 

[SacredGroove]

Try it in V2 of your Blackface.

 

[BigBrewtus]

I bought a couple of JJ12DW7s and used one in the V1 of my Blackface. I cannot get it to breakup at all now! I think it sounds great! Even with the gain all up its just a very loud clean. Wondered what would happen it I tried the other in V2. Let us know how it turns out.

 

[chacal]

Phase inverter tube does not need to be gainy. 12AT7 at this position increases clarity...

 

[tuna141]

Phase inverter tube does not need to be gainy. 12AT7 at this position increases clarity...

+1

This is where I would try a 12AT7 tube.

 

[Graham Pearson]

The previous 2 posts in this thread lead me to believe that V2 on the module boards is a Phase Inverter. Is that true? I thought V2 was just another signal booster.

 

[JKD]

No, the PI is in the head and is closest to the power tubes.

V2 preamp is on the modules (rightmost preamp tube) and is used as gain stages...you should try the at7, it has a diff effect in v2 compared with v1.

 

[Mister Joshua]

I agree with the PI idea. I'm using 12AT7's in my PI's and they work great. I tried them in my Blackface and they really did not work that well. Just not a good tone. But they are not supposed to be toneful. Thay are supposed to be workhorses. So maybe a V2 swap would work since the V1 is the primary tone tube. Try them both and see how they work. But i like the PI idea. My $.02

Peace, Joshua

 

[Whoopysnorp]

These are great suggestions I wouldn't have thought of on my own, which is why I posted the question here. I'll experiment with this over the weekend.

 

[Graham Pearson]

Here's an excellent article that describes why you shouldn't use a 12AT7 as a "tone generator". The article talks about 2 tube characteristics other than gain: standing current and transconductance. According to the article, a 5751 is very similar to a 12AX7 and can be used as a lower-gain substitute. The 12AT7 is very different and should only be considered as a Phase Inverter.

http://www.guitaramplifierblueprinting.com/files/Phaseinverter.pdf

 

[speedemon]

PI of choice of that late Leo guy from over here in Fullerton. +1 what chacal said.

 

[skilletbone]

I had a randal deluxe that I did the clean mod on and still didnt like it, too bright and shrill. Tried a 12at7 in vi and v2. ended up keeping it in the v2 and found the module more usable, until I got my hands on an extra 12au7. With both 12at7 and 12au7 I had to compensate for the volume loss compared the other modules in my M4. I do only have a couple extra 12at7's around from replacing phaze inverters

 

[Whoopysnorp]

I spent a while experimenting with the 12AT7 in the PI as well as in V2 of my JTM. I like it in both places, but I wound up leaving it as the PI. Might have to order a few more of these tubes!