in the late Sixties I bought a Leak TL50+ for 5 Quid. I built a single ECC83 pre-amp for it that plugged into the pre-amp socket on the leak which provided the power. The circuit I used was essentially the Normal Channel of the Fender Bassman. It worked very well and it was the best sound I ever had playing in the UK. The Cathode biased KT88s really impressed me. When I left the band to get married the bandleader asked me if I would trade it for an actual Bassman. I did as I figured the Fender would be worth more when I sold it.