FWIW… A couple days ago I replaced the stock pre phase inverter MV with the bootstraped MV. Yesterday I played for a couple of hours with the new MV. Today I restored the stock MV, but I added a 220K resistor between the treble pot and the MV pot, plus a 1 MEG resistor from the MV’s input to ground. This is something that I already have implemented on my other 2204 and IMO, it keeps the tones from getting too tinny at low volumes.
However, the bootstraped MV did sound pretty good. Low volume adjustments were a little touchy but still manageable. The downside is just like the Lar/Mar MV, there’s barely any effect from the presence control. I just didn’t feel that this more complicated MV circuit warranted a spot on this amp.
London Power/Kevin O’Connor Master Volume Circuit
Moderators: pompeiisneaks, Colossal
Re: London Power/Kevin O’Connor Master Volume Circuit
Totally agree the KOC master is over-promised and over-complicated. The normal pre-PI one works fine (if you aren't trying to get PI overdrive at low volumes).
If you ignore the MV pot itself, think about what you've done by adding the 220K resistor between treble wiper/MV input lug and 1M to ground? It's just a voltage divider, no different from the MV itself. It reduces the total load to about half and reduces the maximum amount of signal that can hit the PI. Also makes the MV a little less touchy at low settings. But there is no reason it would make the tone less "tinny" at low volumes. In general, I've always had the opposite problem, sound is dull and too bassy at low master settings.
If you ignore the MV pot itself, think about what you've done by adding the 220K resistor between treble wiper/MV input lug and 1M to ground? It's just a voltage divider, no different from the MV itself. It reduces the total load to about half and reduces the maximum amount of signal that can hit the PI. Also makes the MV a little less touchy at low settings. But there is no reason it would make the tone less "tinny" at low volumes. In general, I've always had the opposite problem, sound is dull and too bassy at low master settings.