I found good help in this thread and would just like to share my experiences so that anybody with a similar problem might benefit from them.
I have built 4 BYOC kits without any problems. The fifth - the FET Preamp - is the first build to give me any trouble. I found this thread and it helped me locate the problem.
The symptoms were:
- Red LED comes on. Good, we have power.
- Volume control works "in reverse". From half the bypass volume to silence.
- The tone controls have very little effect on the sound. In fact only the bass and low cut controls made any discernible difference.
After reading this thread I of course figured that the OpAmp IC's were faulty - it couldn't possible be a problem with the build
Just to make sure, I went through all the suggestions in this thread.
Switching the IC's had no effect. In fact removing both of the IC's didn't change much. Maybe the tone controls had less effect but not by much.
IC2 had 9V from pin 4 to pin 8, and 4,5V from pin 4 to pin 6. IC1 was a different story. No voltage on pin 6 or pin 8.
Turns out I had skipped pin 4 when soldering the socket for IC1. After fixing this small problem I measured the expected voltages on pin 6 and 8.
Now everything works, and I agree, it is "Amazing how good a pedal with high impedance MOSFET input and a real active tone control can sound, innit?"
Thanks for the help.
PS: And for my next build I have the E.S.V. 2-Knob Bender (OC75) from my local distributor. Sorry, they are now out of stock too.