Echo and Distortion circuit

[PraiseIommi]

The link below is a schematic of an echo and distortion circuit I have breadboarded. The echo effect is working, as well as the distortion, but I find when I adjust the potentiometer on the op-amp which controls gain it can get very noisy the higher it's set and I'm also getting constant feedback at higher gain as well. When I initially breadboarded just the gain stage by itself, it did not sound this noisy, but integrating it into one circuit, including the PT2399's for the echo effect I am getting different results. Any way I can maybe resolve this? Any advice on the schematic is also appreciated and of course any questions you have as well. Thank you for taking the time to read this, hope everyone has a nice day.

https://drive.google.com/file/d/1hi6wpTtJGAkBkRN5D1iz1qOIKlrUQH4t/view?usp=sharing

[blackieNYC]

Are you hitting the 2399s too hard if that gain control is up?

[ElectricDruid]

Are you hitting the 2399s too hard if that gain control is up?

Yes, they are! The TL074 op-amp will clip at about 7Vpp. The PT2399 can only cope with about 3Vpp before it distorts, IIRC. The input signal will push the chip beyond the limits of it's power rails, and it may well not like that.

I'd add some clipping diodes to ground after the gain stage. That will give you more controllable distortion, and the clipping threshold will keep the signal at a level that the PT2399 can cope with. Single diodes in each direction will give you very heavy clipping but a reduced level (0.6V in each direction is 1.2Vpp). A series pair of diodes in each direction would give you about 2.4Vpp, pretty much perfect. You've got plenty of gain so you'll still get heavy clipping. Currently you're clipping at the op-amp rails of 7Vpp so it'd be a bit *more* clipped than your current set-up.