I've built myself a Two Knob Express preamp and married it to a 5E3 deluxe cathodyne PI and output section,
housed in Swamp Mahogany TV Front style cabinet.
I was looking for something smaller in wattage and volume to take to small gigs / rehearsals etc , my Express clone is a little too much for that
![Very Happy :D](./images/smilies/icon_biggrin.gif)
I started out with rfgordons TNT schematic which is great outta the box, but the tweaker in me wanted some more adjustable gain, both more and less.
I played with the V2A section of the Express/Liverpool , did the adjustable pot on the 150k to ground resistor but decided to got back to fixed settings, I ended up with Mark Abbotts suggestion on one of his Liverpool drawings of 0.0022 and 68k ...
Next I decided to play with the cathode resistor value on V2A. KF has it at 10k which induces the cold clipping into the PI, so I decided on a 4 way rotary switch to give me some variations , the 4 resistors I decided on were 1.5K (Leo Fenders go to) 4.7k, 10k , and 22k .... I went as far as the Soldano 39k in my experiment but with the 5E3 phase inverter it was too much
I'm pretty happy with the mod , just trying to work out how to stop the popping when you switch between settings ... any ideas ?
Here's the schematic if anyone wants to try it