Troubleshooting 3.0

Hi,

Yes you should be able to get a gain around 21 times (the formula for that non inverting op-amp is G=1+(100K/4.7K)).
Maybe there is something wrong in your circuit around the trimmer resistor, C3, C4, R4, R5...

Did you try to listen to it with the maximum gain that gives you a peak to peak signal of 2V at the output pin of the input op amp? is it better?

You are right, the offset value between pins 5 and 6 should not be that big, maybe something wrong in the feedback loop (trimmer resistor, C3, C4, R4, R5) is making the op-amp to change that offset.

Yes, is definitely something weird with the signals at the op-amp pins.
Sounds silly but are you sure that is not plugged upside down or something like that?

I think that you tried before on a vero board that part of the circuit with the op-amp and you made it work, It is as simple as replicate this little part.... on the pcb you can see all the tracks and all the connections so you can try to see if you can replicate the connections and follow them on the PCB.

The circuit is not complex, just placing the part in the right holes and having them connected makes a successful build. I have seen some Arduino UNO replica boards not having good ADCs and some dodgy IC sockets but right now I cannot see where is the problem...

Hi, no, you cannot place the LM741 into the pedalSHIELD UNO board. It is a single op-amp and you would need a double.
But maybe you can take the TL972 from the pedalSHIELD UNO board and place it into your veroboard and see if it works fine there...

Hi the LM358 is not a rail-to-rail op amp which is what you need here, it will saturate at 3.7V (when supply is +5V and 0V), but if you dont apply much gain you can use it just as a test, the pinout is compatible with the tl972 and there is no harm trying it.

The tremolo effect is maybe one of the most noisy effects, because it modulates the input signal with a sinewave, and if there is noise at the input it also modulates the input noise making it more noticeable...
Maybe we should re-write that effect just attenuating the input signal so the input noise never gets amplified.... I will think about it.

Have you tried using a different power supply to see if the noise is still there? pedalSHIELD uno is pretty quiet by design.

Hi, thanks for your work on this!

Firts of all I dont really get what do you mean when you talk about shorting pins 3 and 7.... are you talking about the 3PDT?

Again when you talk about a cap between pin 3 and gnd is not clear for me which pin 3 are you referring.

The cap C5 togueter with R6 forms a low pass filter with the cut frequency around 5KHz, if you increase C5 you may loose some high freq content of the original guitar signal but it may be a good idea.
This week I am out on holidays but as soon as I return I would try your idea.
Regards!

Ok, thanks for making it clear, I will check it out as soon as I am back next week.