SOLVED Integral Preamp Debug


New member
Greetings all,

I am having trouble finding the source of my issue on this Integral Preamp and was hoping for some insight (maybe from someone who's built this as well??).


Audio is at about half and sounds like a zipper powered by battery and 9V supply. Q1 seems to be playing a part in this as signal drops entirely when probed on Base and Collector.

Other notes:
  • Subbed 1n4148 for the 1s1588 diodes per recommendation.
  • Used the recommended 35V capacitor values.
  • I have used (and substituted) known-good TL072CP and TC1044SCEPA chips.
  • Q1 and Q2 are BC548C per recommendation and measure appropriately prior to soldering on to the board.
  • R4-6M8 resistor is 4M7 and 2M2 wired in series.
  • I have reflowed all connections at the jacks, grounds, and switch.
I suspect Q1 may just be bad, but I am interested in whatever other possibilities may lead!

I appreciate any and all help!
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Village Idiot
Sorry for the delay...what voltage are you running to this pedal?
I think you should have around 17VDC for Vref.
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