1 Tube Reverb

[chunkitup]

I have a friend who wants reverb in an amp I built him. The problem is I have only 1 tube available and I noticed most reverbs need 3 triodes. Could someone throw me a schematic for reverb. The clean channel is your standard blackface circuit and the tank that I have is Accutronics 9AB3C1B long decay.

[RudeBoy]

There's this thread on Ampgarage where a one-tube reverb is discussed using an ECL-xx series tube for both driver and recovery.

[txstrat]

I've tried this one tube reverb (see pic). Got the schem from our member tubenit (thanks again).
I left out the first pot and replaced it with a standard 1M grid leak resistor.
Works great. The reverb is not as lush as in a regular fender circuit but wet enough if you don't do surf music. If you still want more reverb you could change the 330k resistor to 270k or something.
Also the taper of the pot is even and smooth (I've used 1 meg audio).
Works in other circuits as well. Just put it right before the PI.

[chunkitup]

Ok so I pulled out TuT1 and most reverbs use 2 tubes or 4 triodes. Now I can modify my clean circuit and free up 1 triode for a total of 3. How could I set up the reverb driver to only use 1 triode and then have 1 triode for the return and 1 for the mix. Or I might just try the scheme from txstrat. My buddy doesnt do surf music he just wants some depth.

[txstrat]

If you need a sound clip to decide if the reverb is lush enough, this is what tubenit posted as link:
Music page of Jeff S S - MP3 music page on SoundClick
Listen two minutes into "rainy blues".

[hasserl]

Check this schematic: http://www.carvinmuseum.com/pdf/amps...r%20REV-E1.pdf

It uses a 1 tube reverb and it works quite well, if not Fenderish, still provides way more verb than I use.

[txstrat]

Hasserl
That looks good especially because it would spare a transformer. You got any soundclips?
Have you tried it with no recovery triode before the PI?

[hasserl]

Hasserl
That looks good especially because it would spare a transformer. You got any soundclips?
Have you tried it with no recovery triode before the PI?

No clips of the verb, but I could probably come up with one. That is a Carvin amp circuit, I've done a lot of mods to it, but not to the reverb.

[txstrat]

Would be great listening to it at "normal" and full verb settings.

[Alexander]

sleeper 1-tube reverb tube; JJ12DW7

Hey TXSTRAT,

Try your same circuit but with 'AU' triode (pins 1,2,3/P-G-K) driving xfmr from JJ12DW7/ECC832, just keep plate volts at 300-325vdc max. Those 'AU' triodes crank out close to 5W, drive pan much better than a 12AX7 triode. But still not surf reverb but will make 99% of reverb users happy. Use a 1M dwell pot on front end of circuit for great 1-tube/2-knob reverb!

[txstrat]

Hey Alex,

thanks alot for your hint.
It never came to my mind to use a 12DW7 although I have used it in one of my builds.
I'll definitely try it. Do you think I can keep the grid leak and plate resistors? Voltage now is around 255v?

[Alexander]

mo' verb details

I'm assuming your 1st plate is connected to the typical Fender reverb xfmr; they're usually set up for paralleled 12AT7, a single 12AU7 triode is about half that Z but they still seem to work well and have good life as long as you're not whackin' them with 400V like in a typical fender BF/SF amp. Use a bigger cathode R, IIRC 3.3k/1W works well, and use no bigger than 1uF/50V bypass cap, we don't want to amplify bass freqs in the pan circuit! smaller is better here!

In lieu of 220k-1M grid load, why not use 1M or 500kA pot for reverb 'depth/dwell' control? This way you get 1-tube, 2-knob reverb!

The 'recovery' amp side of the 12DW7 uses the same 82-100k plate R, .001 coupler to PI or blend/level pot. Consider it 1/2 12AX7.

HTH,