hi all, I just built this same pedal and I'm having the whistle oscillation sound as well. I am using a TL071. I was troubleshooting and referenced the data sheets. I noticed the TL071 has a different pinout than the LM308. Pin 8 on the TL071 is not connected. the pin 5 on the LM308 is not connected. Initially i was not getting audio to pass until I used a jumper to get from the 30p cap to pin 5, connecting pin 1 to pin 5) and clipped pin 8 on the IC. I now have sound but I'm experiencing the same issue of the loud whistle. I tried removing the 30p cap and it doesn't change the whistle. I also replaced the A100k pot on the filter with an A25k (didnt have A50k on hand) and there is no change in the whistle.
I checked each component during install to make sure the values were correct. I have also checked the caps, diodes, IC and the JFET for proper orientation.
Any ideas what could be causing this?