Reverb drive and recovery- reconfigurable as overdrive?

[Whiskeyrebel]

I have an R12-R Reverberocket, 2 x 6V6 with octal preamp tubes. Is there anthing I could plug in between the drive and recovery sections in place of the tank that would get the one to overdrive the other? Does it just need a voltage divider to get the levels right or does it also need a transformer to isolate the sections? I know, why would I trade that Ampeg reverb for fuzz...

[Whiskeyrebel]

bump - anybody?

[donnyjaguar]

This won't workthe way you may be thinking. The reverb, or wet, signal is run in parallel to the dry. If you remove the tank and jumper it over, even with appropriate attenuation, there's a high liklihood it will feed back into itself and start oscillating. If you're lucky and the phase is 180 degrees out you may be able to get some overdrive tone but this will be mixed with the dry signal and sound a little odd.

[John Phillips]

It will usually work, because the send signal is so much more powerful than the return is expecting - and even more so than the dry signal, which will be padded down to match the return at the reverb mix stage - that even if they're out of phase, it will drown out the dry signal almost entirely. This is exactly how the pull-boost circuit on the 1970s Fender SF Twin and Pro works (which is perhaps not much of a recommendation! :)), and the Lead mode on the Super Champ and Princeton II (which is maybe a little better...).

You could even buy a little box back in the late 70s or early 80s to do exactly this, on reverb amps (it was designed for Fenders, and plugged directly onto the reverb tank jacks, but will probably work on others if the spacing is correct or you add jumper cables). I think it was called the 'Ice Cube', but I could be wrong.

If you're going to do anything like this, you MUST properly load the send, since it's effectively a small tube output stage, and if you don't you may well blow the drive transformer. Most reverb tanks designed for tube amps seem to be in about the 10-ohm range on the input - so you'd need a 10-ohm resistor of at least a couple of watts power rating - but it's important to check first. Measure the resistance of the input side of the tank and double the reading, for a good guide. The resistor should be the next standard value above that.

[Whiskeyrebel]

http://www.freeinfosociety.com/electronics/schemview.php?id=823

This shows no transformer between the drive section's tube and the tank, and does not seem to give any info about the tank. I found a company called Recycled Sound that is making a sort-of reissue called the ice box, and sent 'em an email, so let's see what they say....

[donnyjaguar]

I just had a look at the schematic. This amplifier is wired quite differently than your typical Fender, which I'm most familiar with. There doesn't appear to be a transformer driving the reverb tank at all. And the tubes used are the lower gain 6SN7. The good news is the input to the reverb is largely isolated by a differential amplifier so the liklihood of it feeding back is quite low. That said, it should be easy to experiment with a lone resistor connecting the Send to the Return to attenuate the signal. I'd suggest starting with 2M2 and reducing value once an appropriate level is found. (this because I don't know how lossy the reverb tank normally is).

If your schematic isn't the same as this one (http://users.aol.com/portaflex/schems/r-12-r.gif) then the above may not hold true. As John says, the overdrive signal from the reverb should be enough to overwhelm the dry signal, although I have to admit my experiments with Fenders weren't like this so YMMV.

FWIW, I'd be more inclined to modify the tremelo circuit into an additional gain stage.

DJ

[John Phillips]

I'd be inclined to leave the amp alone and use a pedal, if it isn't a simple case of making some external connections. There's no guarantee the result of modifying the amp will even sound the way you want.

[donnyjaguar]

I find myself also in agreement. A lot of players seem to strive to get that balls out killer tone but I have no problem achieving it with one of my overdrive pedals anyway.

[Whiskeyrebel]

No objections to pedals exactly. The Reverberocket sounds really good when I beat up its input with an LPB clone (doubt me if you must).

I'm just trying to pre-plan a way to set up a rig with a switcher that I have. The switcher has 4 loops and 4 relays for switches, and the loops are already spoken for. I guess if I rigged up a relay inside the boost, it would activate from the switching relay.