Hey all;

Still plugging away at trying to rid my guitar fx pedalboard of switching
pops. I've tried a couple things recently that may shed some light on the
problem:

I star grounded all the grounds from the in/output jacks to the middle leg
of the 7809 regulator. This greatly improved the DC offset I was measuring
at various points (everything is now within a few 10ths of a millivolt), but
made no difference in the pops for anything that used a relay, but the amp
functions (switched by the transistors in the bottom right) are much quieter
now (any ideas why this might be)?

When the pedalboard output (via the noise suppressor pedal) is not actually
plugged into the amp, the amp functions are quieter still.

This is leading me to believe that there is something other than DC offset
or relay noise causing me grief. I finally put my scope on it, and with the
probe attached to any of the in or out pins on the ULN2003, I got an AC
spike of about 10 - 12 volts, maybe 50mS long. It is negative going when
that particular effects is selected and positive going when I hit bypass.

Is this an odd reading to see, or is that what you would expect? Am I just
reading an inductive spike there from the relay closing? If so, I thought
that was what the diodes (both across the relay and in the 2003) were
supposed to prevent. Or should I not be using the diodes (i.e., not connect
pin 9 to 12v) in the 2003?

Thanks for any input.