The first step was to review the various reverb drivers out on the web. There were several solid state designs, including those from Accutronics.

But since this was a tube amp, I wanted tube-driven reverb. Having owned several Fenders over the years, I really love the Fender reverb sound. I finally found an ingenious design by Dan Souder (click photo on right for full-size schematic).  One thing you need for a Fender-type reverb unit is low impedance in (normally 8 ohms) and hi impedance out. Dan used the 8 ohm output of his amp's audio transformer as input to a reverb tank, then used two sides of a 12AX7 to drive the output.

Once the circuit was selected, it was time for a prototype.

After finding all the parts, I cobbled up a spider web of wires and components to create the prototype. Talk about true point to point construction!

Next step was to make the connections to the amp. These included (1) heater wires, (2) signal out, and (3) signal back in from reverb. Use caution if you try this, because you'll have over 240 volts exposed outside the chassis. Lock out the dogs, wife, and kids.

The fuse didn't blow after we applied power, so it was time to see if this thing really worked. Here is the basic test rig. Input is from a 1992 USA Strat Deluxe Plus. I used the reverb tank on my old Super Reverb for the test. I fed the reverb output signal back into the input jack on the amp (see schematic). Output from my little homebuilt amp went to a 1966 Guild Thunder I.

Despite the rat's nest of wires and total lack of shielding, there was remarkably little hum. The old Guild seemed to really like the buttery sound of the Fender reverb tank. Here is a short recording. I apologize for the lack of audio quality; I recorded it on my laptop with a cheap headset microphone.

Cut 1: Prototype Reverb

Other sound cuts.

I am very pleased with this reverb. By adding a switch and reverb tank, the amp can go seamlessly from a sweet 6 watt singer to a stand-alone reverb unit. Next step is to build the head.