Circuit Understanding

Hi everybody! Nice project!

I have some question on understanding the circuit:

1. How do I scale RV1? Do I have to check the amplitude of the signal first? Because I want to use it in my FX loop and I donot know the output level of my FX Send. My understanding from MXR Micro Amp is, that it is one of the control knobs, so in this case the Level, but if so, wouldn't it be mentioned in the interface section of the circuit? And why are there only 3 knobs on the pedal if there are RV1 to RV4?

2. Is the +3.3V supplied by the +3.3 pin of the arduino to the whole circuit? So I just connect for example the T1 and the RV2 to this pin?

I would be grateful for your answer.
Kind regards
FX Loop Guy

Thank you, you were already very helpful!!

Another question about the circuit: The IN_BUFFERED from the Input Stage will be connected to the IN_BUFFERED from the Output Stage, right?

The VR1 trimmer will set the input gain of the input stage (between 1 and 20) once you set it for your guitar (or input device) you wont need to move it. I usually adjust it by ear, when it sounds distorted I turn it a bit down and that is all.

But then I can only go louder, can't I? Because if the signal is for some reason let's say 4 V and I need to attenuate it, I cannot do it in this configuration, because the lowest amplification factor is 1.
What makes sense to me, is that the signal needs to be amplified to the full voltage range of the Arduino pins, to get the most precise signal processing possible. But wouldn't this configuration always boost the input signal, bypassing the Arduino via IN_BUFFERED, as well? So that you always have a boosted signal?
(As I mentioned above, I am not sure, if I got the purpose of the IN_BUFFERED correctly. I understand it as a switchable bypass of the Arduino, to add the "raw" input signal to the modified input signal on the output, e.g. for a delay effect.)

Yes, the 3Ve comes from the Arduino board, and I dont understand what do you mean by "I just connect for example the T1 and the RV2 to this pin", could you explain it a bit more?

You already made it clear to me, thanks
I was just wondering, if there is some other voltage source of 3 V where I need to connect the T1 and RV2, or if it is the +3V3 pin of the Arduino.

Hello,

I've successfully built the pedashield from scratch, uploaded the chorus program and attached a sine wave pattern to the input and my scope to the ADC input (opamp output)

I noticed there's some serious clipping going on. And adjusting RV1 isn,t changing anything to the input signal.
Is this normal or should i look for an error in my input stage opamp?

output stage seems to be working fine. Mixer too.

i'll attach the scope image and the image when i simulate the input amplifiers

1vpp or 0.35Vrms sine wave.

normally the amplification factor of the first opamp should be adjustable from 0.2 to 21 with the RV1, no?

(function generator is on the left of the scope image)

Hello Ray,

It's definitely at the input stage that the opamp goes awol.

i measured on the inverting and non-inverting outputs.
i've attached my results in attachment.

Have you encountered similar problems with the input stage?
What is the best way to debug this one?