using the 470pf/470K tone filter with a Fetzer Valve stage

[mordechai]

I want to incorporate the classic Marshall 470pF/470K tone filter after a Fetzer Valve stage leading into Mosfet SHO type of circuit.  Should I incorporate the filter before the 100KA pot at the tail end of the Fetzer circuit, or after it...and if the latter, should it go before a coupling cap leading to the Mosfet, or before?

[mordechai]

Let me bump this since nobody responded the first time...where should this 470K/470pF filter go if using it with the Fetzer Valve in a larger chain of FET stages?  Between the FV's output cap and the output pot, or after the output pot before the next gain stage...and if the latter, then before or after the coupling cap for the next gain stage?  I've looked at the way it's used in the ZVex Box of Rock, which is all MOSFETS, so I'm just not sure where to place it between a JFET block like the FV and a MOSFET block that comes after it...

[Quackzed]

i'd say between the output cap and b4 the output pot, but you may want to sub a 1M output pot for the 100k;  with a 470k/470p filter your gonna be cutting the fetzer volume to 1/6th of normal with a 100k after, where with a 1M after your only cutting it to 2/3rds or 66% of full rather than 17ish% of full with a 100k... its after the out cap so it shouldnt affect bias either way and you'll also get a higher input impedence into the mosfet stage...
BUT a filter like that needs a certain load resistance to give you the 'proper' responce you want, so you might have to scale the filter either way...
ok wait... the jcm800 uses a 1M pot right after the filter so i think you'll be fine with a 1M, if you try it and its too trebly you can SCALE the filter to where you like it ...
halve the resistor and double the cap, see if that gets you closer, if it gets you further away do the opposite and double the resistor and halve the cap value...
not enough, do it again re-double one and re-halve the other up or down depending...this keeps the filter relative to itself and adjusts it for the load.