Unique feature for an overdrive pedal?

[niektb]

I hear the background noise subtly darkens but nothing noticeably happens to the guitar tone... I double-checked schematic and part values on the board, they're all correct. Anybody an idea on what's going on?

To me the impedance of the bridge-T network is too high for the 10k load.
You should see a large gain drop until the 100k pot is set to the 1k side (ccw on you schematic).

Try temporarily (or permanently) moving the 10k at the input of the second opamp to just after the 1k ie. before the added mid tone control.

Check your DC voltages.

The mid control works super nicely, it's the tone (or high) control that doesn't. However, I think I figured it out! I ordered film caps with 220nF but the package they sent contained 22nF  no wonder it performed so badly 

Edit: Oh, seems I forgot to add my latest version of the schematic   

you mentioned that you wanted to ditch the transistor buffer for better noise floor. the transistor will take any power noise and multiply it. you don't need to eliminate all transistors. you only need to reduce power rail noise. an opamp will still have power rail noise but that noise is pretty much as-is for ripple on a single supply buffer. they both benefit from power decoupling but the transistor will benefit more.

Not ditching, but replacing them with transistors that have lower self-noise (I replaced the BC547 with the MPSA18)

What program are you using for designing the PCB? Also, what spacing do you use for the footswitch and I/O jacks? I'm using Eagle at the moment and I'm not able to figure out those nice PCBs like the one you have there

I use Eagle too! There should be some button that says 'Switch to Board Layout' (or something) just click that and you can draw your own PCB

[alfafalfa]

Hi Niektb,


I saw your schem and noticed R18, R19 are indicated as 0, does this mean they are 0 ohm ? Then what is the function of them ?

Tia, Alf