SOLVED Hiss from AION RC/AC booster circuit - How best to debug?

[harmaes]

I build the latest RC/AC booster PCB from AION again and socketed the different components.

Started with the AC and noticed there was a very prominent hiss coming from the build. All controls were working with their normal range, volume can go well above unity etc. I built it before and had the original pedals so I have an idea how they’re supposed to work.

I tried various opamps (5448P, 5448DD, OPA2134, TL072) and all were generating hiss, so its likely not the opamp causing issues.
I decided to swap the components to try out the RC. Again the same issue with hiss.
I mean with hiss a constant noise that changes prominently with increasing the bass or treble and volume/drive of course. The Lone King I finished yesterday also has noise which most boost or drive pedals do, but when turning off the guitar volume it normally goes away. The hiss from this circuit is constant.

I tried using an audio probe and I noticed that in the circuit the hiss starts to build up, in the clipping section of the opamp and on its output it’s increasing a lot, but maybe the noise starts earlier in the transistor etc? My specific questions are:

- Is it possible to measure the transistors (2n5088) and how would that work? What voltage to expect? Since replacing the opamps didn’t change the amount of hiss I’m concluding it’s not opamp related.
- Which components are most likely to influence/cause hiss? Is there an order or specific way of probing or measuring?
- Can clipping diodes increase hiss for instance?

Circuit doc is here: https://aionfx.com/app/files/docs/malacandra_documentation.pdf
i will post a pic later today.

Thanks for your help!

 

[jesuscrisp]

Detailed pictures of the build first, otherwise everyone just posts their favorite pedal building mistakes.

 

[harmaes]

Detailed pictures of the build first, otherwise everyone just posts their favorite pedal building mistakes.

Done!
I had to patch the 1uf C1 to the 1M resistor at the bottom because the connection (and continuity) on the pcb was broken from removing the socket

 

[PJS]

What are you using for power? If you are using a power supply try it with a battery

 

[harmaes]

What are you using for power? If you are using a power supply try it with a battery

I’m using coiks power supplies, never had any issues with them and using them with the Complex overdrive and the Lone King from PedalPCB which have more gain. No hiss, noise from the guitar amplified yes.
I built vero and older PCBs of the RC and AC booster and never had this issue with constant hiss.
First thing I want to try is removing the transistors and socketing them and trying out replacements.

 

[harmaes]

Ok solved, 2 replacement 2n5088 solved the hiss issues.

Can you measure transistors to check if they’re faulty?
Either they were delivered broken or maybe I overheated them.