Super Heterodyne: Noise but not the good kind

[Quirkey]

Hey All! I made a promise to myself that I would get through my backlog of half working/unfinished pedals before I spent any more money on parts so ... (I'm sure I'm not the only one here)

I started this Super Heterodyne months ago but it wasn't working right off the bat and I didn't have the energy to debug at that point. I had a feeling that some of the CMOS chips might be bad as I had similar issues with my Flock Fuzz build. I used my working Flock as a test bed and was able to eliminate a few bad cd4017 that I had from eBay. At this point I got sound but it was like a constant square rumble as if there was a lot of noise coming into the input and then being amplified through the PLL. I was also worried it was the 40106 and ESD so I built a little test bed on a breadboard (based on this great video) and that seemed to work as advertised. So I was further stumped! I decided to audio trace and from the beginning I had trouble understanding what was going on in this initial section:



After the first opamp the signal seems to get quieter and then through the CD4069 inverter the signal seems to just get noisier. It seems based on the schematic that the 40106 is supposed to generate the "square" version of the signal?

Can someone help me understand this?

 

[jcpst]

“I got sound but it was like a constant square rumble as if there was a lot of noise coming into the input and then being amplified through the PLL.”

I just put one together and this is the same issue I have.

My working theory right now is that there is a ground loop loud enough to trigger the osc. But not sure / haven’t found it yet.