OK, solved it , tuned the trimmer at Q5 by "ear" to remove the hiss
and this works great now 
Happens to be 7.1v !!
Sounding great now, many thanks Mike.
Marty.
That's GREAT! I'm really glad you like it
- that's a great suggestion to also give the drain voltages on the FETs - I will do that tonight when I get home. For those that might not know though, JFETs, especially J201s, have differing gains - more so than Si transistors in a lot of cases - and someone else's voltages may vary from what I use. This circuit is one of my quieter ones due to all of the Miller emu caps, hissing is not one of the things I had encountered while adjusting the trimmers - I will see if mine does the same thing.
What do you guys think of this procedure below? It's what I started doing after building (re-building
) a bunch of these JFET distortion circuits: I do the following to get the voltages just right:
1) set up the drains on the FETs to 1/2 the supply voltage - this should make the circuit pass a sound
2) starting with the last FET before the output, the last FET in the circuit, tune by ear for the loudest output. In the case of the Plexizer, tune Q5 to be the loudest possible
3) then, repeat #2 for Q4, then Q3 then Q2, then Q1
Now, #4 and #5 are the tough part as it's really subtle - but IMO really makes the sound of a circuit like this (or the Dr B, ThunderChief...) more authentic
4) then, crank the gain up to max with all of the tone stack maxed, volume slightly higher than unity - 3db should do - hit an open d string on the guitar and tune Q4 until you hear the first harmonic come out a bit better about 1-3 sec after you hit the note - I warn you this is a tough tweak with a single turn 100k trimmer, but after some practice...
5) repeat step #4 for Q5 - Q5 seems to have the more dominate affect - now the 1st harmonic should be pretty easy to hear mid-neck on the middle strings and pinch harmonics should be fairly easy.
I think it would also be interesting to see what others think of all of these 'cousin marshall-ish' circuits when used on the same pedal board (not at the same time..)? I think this one, Electric's JCM 800 Emulation, the ThunderChief, and the Dr Boogey (respectively) cover that whole spectrum - what you could want from a distortion box - very well: Keeping in mind - for overdrive there is another world of circuits, and for sonic destruction there is another world of circuits in the realm of rats/fuzzes. I'm thinking with some carefull CD40XX switching one could put them all on the same board utilizing all of the common bits of these circuits; this might require dual-ganged pots for the tone stack and some really good debouncing - thoughts?
