that dual clipping idea seems interesting, how does it fair with guitars with insanely high output? i have had some disappointing results with soft clippers in combination with that guitar.
one thing tho, the first gain stage's NFB terminates at the Vb, shouldn't it terminate at ground? i feel like the low resistances would bootstrap and influence the gain via the Vb
Andy, cant wait to see your idea
cheers and Happy New Year, Iain
That's what I thought, as well. But it didn't work. Had to tie those ground legs to Vref to get anything. I honestly don't know what the relative output of my various guitars is, though I have an old Vantage with some double-creme Schaller pickups that might fit the bill. I'll try it out and report back.
As for how to make the circuit handle hot pickups, I suspect the answer is to be found by reducing the value of that 20k feedback resistor, and maybe letting the 20k and 12k resistors trade places. As shown stage 1 has a max gain of around 55x and stage 2 has a max gain of 18x, yielding a combined gain of just over 1000x (

), so more aggressive than a Bluesbreaker but not quite into Rat territory. Set to minimum, stage 1 has a gain of 10x and stage 2 a gain of just under 2x, yielding a combined gain of 20x.
If we switch around the 20k and 12k resistors, we get a combined max gain of just over 570x and a min gain of just under 12x. So that ought to handle hot pickups a little better.
The basic idea of the circuit is that stage 1 provide a pre-clipped signal with suitable treble cut, that is then pushed a bit harder in stage 2, and re-clipped, again with suitable treble cut. The stock Bluesbreaker strikes me as providing insufficient bandwidth-management until one gets to the tone control. Maybe that's why it is so strident to my ears. Much like a TS-9, the gain in stage 1 also loses top end as gain is increased, such that things like two-pickup "cluck" are still quite audible at low gains, but the tone thickens up when gain is cranked and bandwidth of stage 1 gets decreased.
Again, I have to give credit to the genius of the gain control in the Bluesbreaker.
Andy, do whatever makes you happy. Me, I have no urge to protect I.P. and get my kicks from simply having something work out as intended.