Anyone Interested ?

[Rob Strand]

Are you sure about R14/R15 values, Rob..??

I'm quite sure.  The Washburn schematic and the hand drawn Audioworks schematic have the same parts.
(There is a cluster of three Radial package Electrolytics at the centre of the top-edge of the photo.
Under that are three resistors 1k, 100k, 1M.  The green band of the 1M can be just made out by enhancing the photo.)
There are four gain stages after all.

[Rob Strand]

I found a post on another forum that implied the guy who designed this was the same guy who designed the MXR Distortion+.  True or not I don't know.


The tone control would work better with a 100k pot instead of the 500k.  The boost/cut of the tone controls will be bunched-up at the ends with the 500k.

[Rob Strand]

There's one hanging issue: the DC coupling of the opamp to the first stage.
Anyone want to give it a check?
-U1 is the opamp at the bottom left corner.
-Q3 is the lowest JFET just right of the vertical centre line of the PCB.
  Top view pinout for Q3 is \ d s g /.
-The right hand side of the board is the JFET stages and the opamp used for EQ.
-R7 is the lowest resistor just to the left of Q3.
-The long jumper from U1 pin 1 to R7 is the one covered in plastic.
As I mentioned above, my argument is there's no cap between U1 and R7 ,
or between R7 and Q3.

An alternative view is the plastic covered wire is the leg of a cap and the cap
is obscured.  The distance between the two holes is about 1 inch (25mm) which
isn't too long for a part to stretch.

Cap Fixes:

1) Confirmed C7, C9, C10 are in fact 30n
  I can see "303" marked on C7
  (As both Hand-drawn and Washburn schematics show)

2) The ceramic C3 is  30n.
  I can see "303" marked on C3.
(This doesn't agree with Washburn or the Hand-drawn Audioworks schematic.)

3) Is C2 50n or 30n?
  Wasburn 50n
  Handdrawn Audioworks 30n
  Part-size on the PCB looks like 30n's not 50n, so I'm going with 30n.

[Rob Strand]

JFETS:

Due to the high Rs value, the ideal biasing point is probably a bit higher than Vdd/2, perhaps,
   Vd = 5.6V
        Vs = 2.2V

Some candidate JFETs (Q3 through Q6) are,
BF245B   Vd=6.1V, Vs=1.9V
2N5485   Vd=5.7V, Vs=2.2V

The Pinout seems to match BF245.
So, I suspect the original was a BF245B.

JFETs do vary so you may very well need to tweak the drain resistors anyway.

No doubt J201's will give more gain but you will have to change the circuit
to bias correctly.