1 tube reverb?

[Chuck H]

Here's a better idea: Google search for speaker driven reverb.

First... Your choice of wording is intentionally rude and I take offense to it. Asking for information or even example circuits is pretty common around here. You could have said "You just need to look up speaker driven reverb" or offered a model number. You might even have abstained from responding. That post demonstrates the social graces of a canker sore.

I've built a speaker driven reverb. And I've seen all the examples done on early Gibson and Hammond amps. I thought I researched it pretty thoroughly. I haven't seen any examples where the reverb is driven from the amps output and fed back to the same amp. Just to a separate amp.

If you actually have something to offer, and aren't just regurgitating notions proposed in KOC's book, as you've been known to do, let's have it. We'll know soon enough if you actually DON'T have it then.

[jimboyogi]

First of all guys, to those who seem to think i'm still using 1/2 the tube for the other issue, i have a single TUBE, not a single stage. So i have 2 stages. As i said, the one stage i was using to fix my level/tone issues at the PI is not longer needed ow that i discovered cbarrow7625's suggestion for a master volume worked even better than the extra tube. So i have a whole tube, but still from what you guys are saying it's not likely to work well so i think I might pass rather then create another mile long thread. But if you think it can be done w/o jumping thru hoops and wanna have a go with your ideas, be my guest. Sorry about the schematic. I had uploaded it but forgot to add it when i started the thread.

[ATTACH=CONFIG]27923[/ATTACH]

This idea is using a 12DW7, one 12AU7 triode and one 12AX7 triode in the one bottle.
Have a look at the 12AU7 circuit down the page a bit here - The Valve Wizard
Try just using the one 12AU7 triode instead of both triodes paralleled, but stick with the 22K resistors, and the 0.47uF coupling cap. Try a 1K unbypassed cathode resistor. Tap the signal off from after the first gain stage before the gain pot, via a small cap (500pF to 1nF) to the 12AU7 grid, with a 1M grid leak to ground.
For recovery, use a standard high gain circuit using the 12AX7. After the output coupling cap, try injecting the reverb signal back into the dry circuit path somewhere between the 2nd and 3rd gain stage. You will need to use a pot with one end to ground as your 'reverb' pot. It could be a 250K pot replacing the 220K voltage divider shunt resistor, but you may find that the reverb signal will be too attenuated by the divider here.

Also for tanks I recommend a 3 spring short tank, long decay, high input impedance, either accutroniccs or MOD, they both sound good.

[loudthud]

The Champ 12 has a speaker driven reverb. Link: http://www.el34world.com/charts/Sche...p_12_schem.pdf

There is a note at the lower left corner of the schematic on how to set the level so it won't feedback. I think this was a Paul Rivera design.

[Chuck H]

Thanks LT. I did find that schem so I did some research. It seems most players consider that reverb weak and tinny. That needs to be taken with a grain of salt since it's a small amp with a cheap speaker and, from what I read, a cheesy little reverb pan. But I did find one story where a guy changed to a better pan and otherwise tried everything he could to make the stock reverb circuit sound better. He ended up retrofitting a more standard tube driven reverb into the amp. This was my experience when I attempted driving the pan from the amps output and reinserting the reverb signal into the same amp. The best I could achieve without feedback trouble was unacceptably bad. That's why I was interested in any Ampeg circuits that do this. Ampeg amps weren't always rockers but they don't generally compromise. No luck finding an Ampeg circuit that does this as Teemuk said though.

[g1]

And inject it back into the same amp? Not a chance. It becomes a feedback loop. You'd think that the actual reverb itself would be phase ambiguous enough to make it work, but it doesn't. I've tried it.

Ampeg made many amplifiers with such scheme. It works.

The only (speaker driven reverb) examples of Ampeg I can find for this are: Echo Twin, B12X and B12XY. As Chuck mentioned, they all have a second amp picking up the reverb signal, so the feedback problem is avoided.

[Enzo]

R12R

http://www.webphix.com/schematic%20h...rocket_12r.pdf

[g1]

Sorry Enzo, should have been more clear. They were talking about reverbs driven off the speaker.
Edited post accordingly.

[Enzo]

Sorry, I thought we were looking for one tube reverbs. Some Ampeg designs use two triodes, but in separate tubes, at least the R12R uses two sides of the same tube for send and return.


But it that isn;t what you were after... never mind...

Old Hammond organs often had a separate amplifier for reverb. On many, the drive was indeed right off the speaker terminals of one of the amps. Then the reverb amp would have its own speaker for the reverberated signal.

[Gingertube]

I can't find any representative circuits in any Ampeg schematic archives. Could you link one? I'm interested.

Yes Ampeg did this BUT..
The amps were the EchoTwin range etc. They have Stereo Power Amps, The Reverb Pan was driven off one power amp and the reverb pan output went into the other channel - so no feedback problem there.
Cheers,
Ian

[Chuck H]

Yes Ampeg did this BUT..
The amps were the EchoTwin range etc. They have Stereo Power Amps, The Reverb Pan was driven off one power amp and the reverb pan output went into the other channel - so no feedback problem there.
Cheers,
Ian

That's really clever. Nice engineering IMO. Doing it within the same amp seems too problematic as evidenced by the lack of representative example circuits and, for me, my own experiences. Point is, there's no sense wasting time on this notion proposed by Teemuk (KOC first, of course). It may "work" from a technical perspective, but only with prohibitively limited performance. I'm done considering it then. Thanks.