Fender Vintage Style Reverb Driver, 125A20B, 022921 & 037099 40-18034 Reverb Driver 125A20B, 022921, 037099 Amps Used In: Most Fender* amps offering reverb. The most common reverb driver transformer. Unlike the common nylon bobbin wound reverb drivers available on the market today, this is a reasonably priced, vintage constructed, paper layer wound reverb driver. This is made just like the originals! BF/SF Super Reverb | fenderguru Replace the 12AT7 reverb driver with 12AU7 – Better reverb control. Reverb is an important character with vintage amps, yet so individual and mysterious. We all know that speakers change their tonal character during age. So does the reverb. The reverb function sounds and behaves differently between “identical” vintage amps. Spring Reverb - Rob Robinette Jul 19, 2017Reverb (short for reverberation) simulates the reflected sound from a room's interior. Spring reverb was invented by Hammond and first used in their organs to liven up the tone in acoustically flat church interiors. Fender licensed the reverb circuit from Hammond and Surf Guitar was born.