Quote from: Brymus on October 09, 2009, 08:11:03 PM
Here is a better way of expressing what I wanted to say before.
If your guitar has a signal of 1V and your pre-amp amplifies it by a factor of 10
Then your last stage- a voltage follower needs to have a gain of .1 to bring the signal back down to 1volt to input your chip amp :tu:
Brymus,
Here is a simple way ,, just hang a 10k pot off the plate *After the HV Cap of course* and run that straight into a SS Amp, Not perfect but keeps the voltage contained a fair bit at the expense of some freq loss. Still the Vtwin idea is better.
Yes I've built this simple circuit and it is very contained,, I've drawn it with the *Drive* switch. If you build it into a pedal the Switch can be Hard wired to a stomp sw,, no relay needed.
The Vtwin circuit makes intelligent use of the massive voltage loss when using passive high imp tone stacks. example; a 10 volt swing looking into the tone stack results in only about 3volts swing out of TStack. Bingo Now the AC signal is smaller and can be handled easily by an opamp. Still you would want to use the highest possible supply for the opamps to avoid any clipping.
Extra Vtwin notes;
C7-22pF (across R3-3m3) is likely to cause some harshness,, try deleting it.
Remember into a Valve power stage this would not be a problem as valve circuits tend to wipe off a lot of exagerated treble response but SS does not develop a lot of natural treble loss. If anything some tend to make it quite harsh as they don't have a transfomer to magically wipe off the HF hash.
This is the one thing that has become obvious to me when swapping identical preamp circuits from Tube to SS Amplifiers, The treble can become extreme.
Again just my tonal taste so some might want extreme treble,, which is why I say R&D First.
Phil.