Speaker Driven Reverb Protection

[jeff]

I want to build a speaker driven reverb amp like the Guild Thunderbird http://schematicheaven.com/bargainbin/guild_thunder_t1rvt.pdf (just the reverb amp part)
or the Falco 510-33 http://schematicheaven.com/bargainbin/valco_superreverb_510-33.pdf
where the signal is sent to the reverb tank from the speaker output.

The problem I see is that I always want to run the tank as hard as I can for the best reverb sound but I don't want to run the risk of blowing the tank. If I set it up to drive the tank to the max with a 5watt amp, I'll probally blow it with a 100 watt amp. Therefore I need a dwell control.

But, is there any way of wiring some sort of meter or LED to monitor the level so I can see when I'm driving the tank to hard? Somehow limiting the signal so it could never blow the tank.
 
And is there any way to protect the tank if I had the dwell set up for the smallest signal and accidentally hooked it up to a 100 Watt amp at full blast?

[RicharD]

My Hammond organ has a speaker driven reverb tank.  They used 2 resistors and 2 #12 lamps as a limiter.  Look at the bottom of my attachment in the dotted line box.  That's the simple & elegant circuit between the main speaker and the tank.  The amp circuit hangs off the tank and drives a separate speaker.  Those Hammond guys were flippin brilliant.

[jeff]

Cool Thanks

I assume sig. input connects to the main amps speaker and driver is the tank input????

The schematic says "volume compressor" does it always compress or does this start compressing when the signal is too big for the tank? I don't know if I want a compressor because it sounds like to me as your signal fades the reverb is still full on, right? On the other hand that might be cool too.

OK, Now I see that's what the dwell is for.

Where would you put the dwell control?

Top to speaker + botton to speaker - and bottom sin. input then wiper to top sig. input?

[jeff]

I just found this

This says limiter. Is it basically doing the same thing?

How exactally do these work?

[PRR]

It's the exact same thing. (Done two different ways.)

"Limiter", "compressor", same except a limiter should be more abrupt. The lamp-trick is such a slop that it could be called either name. (The note is really to tell you that these lamps will never light-up and don't worry about it.)

It limits the drive TO the tank. It does not muck-up your direct sound. It reduces the signal to the tank when the alternative would be gross clanking or smoke.

Still, a HIGH power amp could light then burn-out the lamp. And what is a #12 lamp today?

No fine control is needed; anyway it will just get mis-set in the heat of performance. Use 500 ohms series for up to 25 Watts, 1K series for your 100W monster.