Which Pre-Amp Tubes Do What?

[Rane]

Hi, I have a Mesa Rect-o-verb series 2 and I wanted to experiment with different preamp tubes... Problem is that I don't know which tubes do what.

I have a JJ 12ax7 that I wanted to try in the gain stage and a vintage Hammond 12ax7 that I wanted to try as well. I also have a couple vintage Hammond 12au7's; I've heard that they have more headroom and I wanted to try one of them in the cleans...

I just don't want to have to do the whole "trial and error" thing, and I can't find anything about it on the internet... aside from the occasional mentioning of a "v1" tube slot.

Any help would be appreciated.

Oh, here are a couple of pictures of the preamp tube slots, if that helps you help me identify them. I took the amp apart to mod the effects loop into a series configuration.

Thanks!

 

[Cleekster]

V1 initial gain stage for both channels......also has the most effect on your tone when swapping tubes
V2 2nd and 3rd gain stages of both channels
V3 4th and 5th gainstages of Red channel
V4 FX loop
V5 PI(phase inverter)

your master knob which also functions as you FX send level is right BEFORE V5 so the higher you run your master the harder the PI will slam the power tubes and the more of a "cranked" sound you'll get(mine is set at 12:00)....the Output knob comes right AFTER the V5and determines your overall volume as well as how clean or dirty your power section will run. the red channel with it's 2 extra gain stages can work the power stage harder via more signal strength hitting V5

The harder you hit V5 the less overall volume you'll get before power tube distortion.....depending of course on how much headroom your power tubes have.

for example when i was running EL34'sred channel/vintage)
master-9:00....i would hit breakup othe output knob around 11:00

master 12:00....i would hit breakup around 8:30 on the output

 

[Rane]

Thanks, that's exactly what I needed to know... That also explains why I see so few mentions of using different tubes for a clean channel; they're the same tubes. I feel dumb. :lol:

Anyway, thanks so much, this is very helpful.

For future reference: might it be safe to assume that, at least in a guitar amp configuration, the initial gain stage tube is closest to the guitar input, and the others following thereafter? I mean obviously every amp is different, but could this be said at least as a guide line for changing tubes and such?

 

[Cleekster]

the PI is almost always closest to the power tubes as it is this tube that splits the signal to send to both sides of a push-pull(class AB) power amp.....so yes in general V1 will be closest to your input jack.