There have been a few stand-alone tube reverb units. The most famous is of course Fender’s 6G15 but Peavey, Premier, Supro also made one. Soldano, Guyatone and Dr Z still offer such type of units. While working on transformer-less tube power amp designs, I had the idea of applying the theory to a tube reverb unit and see how it would sound. Ampeg produced amplifiers that drove their tank reverb without a transformer but the results produced mixed feelings (some say they offer the absolute best reverbs, others simply don’t like them). I decided to adapt a particular tube power amp design for high impedance loads to drive a reverb tank.
While the rest of the circuit is derived from Fender’s 6G15, the unit can produce reverb tones with a greater bass and highs content while being less prone to that famous “boingy” sound on the guitar’s attack. The result of the transformer-less design is a well-defined and smooth reverb tone that is more an ambience effect than a special effect: more spacey and less surfy. It therefore works better for high-gain rock or power pop than the 6G15.