This is a weird one. Some 'custom amp maker,' using early SF Super Reverb and Pro Reverb parts, built a BF vibroverb. Its an SFSR chassis, but without the mid knob, the SFPR transformer, a few other changes, and turns out I have a BF-ish Vibroverb. I just did some of those SRV mods, pulled V1, flipped V2 with PI (12ax7 in P1 and 12at7 in V2), going it give it some volume tomorrow, see if I cant get some breakup without blowing down the apt complex. Not a bad trade for a SF vibro champ and $100. Thoroughly been enjoying this thing.