12AT7 as driver for single tube reverb and fx loop ?

[smzinno]

hello all -

I'm working on adapting the single tube reverb and D'lator loop to a somewhat non-Dumblish design, more like a Mezza C+ actually, for my son. The takeoff point would still be after the master volume and before the PI. Does anyone have experience or insight into using a 12AT7 as the driver tubes for these applications ? I have quite a few of these to spare, so I thought this might be a good location to use them. I've read quite a few threads on these circuits, but I couldn't really conclude if there was a strong consensus one way or another.

Thanks much for any help.

[Funkalicousgroove]

It makes a GREAT reverb driver because of the higher current, not sure on the loop.

[Bob-I]

These work great as a reverb driver and a loop driver. The reverb return on the other hand really needs more gain than it can offer, the loop return is fine. I use a 12AT7 in the Dumbleator and it works great.

[smzinno]

thanks guys.

Bob, do you think the reverb return gain is something that can be attained by using different plate/cathode values, or that we can't really get there from here using this tube ?

[Bob-I]

...or that we can't really get there from here using this tube ?

Cain't get there from here

[heisthl]

If you MUST use 12AT7s you will need to use one for the Reverb tank driver (normal in Fenders) and your recovery will have to use both sides of the other, biased somewhat hard to get maximum gain. 2 12AT7 stages should get close to 1 12AX7 stage gain wise. Look at the schematic at https://tubeamparchive.com/viewtopic.php?t=2976 and change the recovery side's values to be more appropriate for the 12AT7. If you decide to base a reverb build on this schematic keep in mind you need to reverse one side of the transformer leads to keep the correct Reverb phase.

[pamaz67]

try the 12at7 in the dlator. if the tube is a good quality one, you have good chances that you'll prefer it over the ax7.
ciao

paolo

[skyboltone]

These work great as a reverb driver and a loop driver. The reverb return on the other hand really needs more gain than it can offer, the loop return is fine. I use a 12AT7 in the Dumbleator and it works great.

Can you use two tubes? Paralleling the second AT7? I got a mess of them too.

[smzinno]

it's not a must-use situation, so I think best bet will be to just use the 12ax7 for the one-tube reverb setup. I'm already at 5 pre's, 2 pwr, and 1 recto tube, so the space is pretty tight already.

thanks to everyone for your helpful replies.

[heisthl]

If tube space is the only consideration and you have circuit and control/jack room you may want a loop instead of the one tube reverb - with a loop you can get any reverbs you want.....

[smzinno]

that's true, although I'm trying to have the reverb on-board, and also have the loop (he uses a lot of FX). I have enough space laid out for two tubes, one each for both a loop and a reverb circuit. what I meant before was that it might be too crowded to use two tubes for the reverb (Fender style), plus a third for an FX loop.

I suppose one other option would be to drive the reverb with one 12at7, use some kind of SS op amp for the recovery, and build the FX loop the normal way with the other tube. keeps all tube in the primary signal path, but I may be over complicating it if all it really needs is an AX for reverb and an AT for the loop.