Note that I am currently building a new vero board with two 3 pin sockets for the FETs. I'll update the pics as I go.

If you scroll down you can see the little jig I have made for testing and comparing FETs.

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This is the latest version of the vero board with sockets for both the input FET and the OD/compression FET. The FET that does the main 'business' is marked with whiteout and blue biro because it tested best out of ten . If you scroll down to the bottom of the page you can see the little jig I have made for testing and comparing FETs.

At right is a handy feature I just put in. Being that the power supply for the unit is over engineered for purpose, I thought it would be a handy feature to have a couple of 9VDC sockets to run other pedals. The PS is easily capable of running a number of other FX pedals, including digital ones. I fact it can run my whole pedal board if needs arise.

To accomodate this feature the three pin 9V regulator will require a small heatsink however, as it will run a lot hotter.

At right is the little jig I have made for testing and comparing FETs. It's basically the immediate circuitry around Q4 with the 1K8 resistor on the drain, the 470R on the source with a 47uF cap and a 470K on the gate to earth. Coupling caps to the gate and drain are 100 nF polymers.

On the oscilloscope display at right, you can see that the amber scan on CH1 at the top is visibly superior to the lower one. It's more even in shape top & bottom, and contains less 3rd harmonic. This will also give better DC stability when driven with short, sharp notes.