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The schematic isn't in the build doc but as far as a can tell looking at the board that pot does not directly control the FV-1. This pedal also uses one of the internal programs in the chip so the programming is there from the factory. I am betting on a poor solder joint or bad pot.

My first thought would be that the pedal is fine and that your power adapter is noisy.

I had a problem with the arachnid board where the connection between the FV-1 and the EEPROM was not soldered well enough. There was enough for multimeter continuity check to beep, but the EEPROM programs were not working. Resoldered the pins and it was fine. It must have been good enough for...

There is nothing soldered into the ground pad that is supposed to ground the input jack. I assume you have that jack grounded some other way? I have found the source of a buzz before by grounding out the audio pathway until the buzz disappeared from the output. What I mean is ground pin 3 of...

That is all a ground lift does. If you have multiple sources of mains power in the system (pedalboard, amp, mixing desk) then a ground lift can be vital. If you are just going pedalboard straight to the mixer with no amp I have never had ground loop problems.

I do like me a bypass switch - just to be able A/B tone and volume when setting up. After that it will probably get very little use :-) I am likely to benefit from a smaller box (125B) because there's not much room on my board to play with. I think I will get an XLR and a TRS and see what I...

I had an original AD9 back in the day and it ran off 18v. You needed 2 9v batteries or an 18v adapter into a 1/8" socket.

Ah yes. It did occur to me that without a footswitch there would be more room for XLR out. Nice to see that it can work. I may do that as well.

I am thinking of putting together a Unicab. The original inspiration has a DI output as well. I mostly don't need that - where I play there is a DI already available so I just plug into that. There have been a few times though when that DI has been missing or broken and having a DI on my...

Are you getting distortion through the clean, or only the octaves?

While you are replacing things - C15 and C16 are melted enough to be very suspicious.

Definitely before you do any more troubleshooting reflow the solder. All the cute little balls of solder are poor joints to the point that they probably don't actually connect the component to the PCB. Get them looking more like above, then we can talk about voltage measurements, audio signal...

I had a similar sound recently with a frog preamp. Different circuit, but the solution for me was to reflow the valve socket - I had initially done it when I was really hungry and a bit shaky, and in hindsight all of the joints looked OK, but some didn't really have as much solder as would be...

Have you gone through the process of calibrating the trimpots?

Your voltages are not making any sense. Make sure you are numbering the pins correctly - also for the LM13700 it is pins 6 and 11 that are relevant for this.

My understanding is that an op amp works by trying to make the 2 inputs the same. If one of them is tied to a voltage (ground or VB is usual), then it will try and make the other input a steady voltage as well. The output then will be whatever is required to cancel out the input, taking into...

That is crazy good troubleshooting

OK, so probe pin 7 of the TL074. If you are getting dry sound at the mix pot then you should have sound at pin 7 of the op amp. Then probe both sides of C3 and both sides of R3. If you have audio at the op amp, but nothing at the input of the FV-1, then it has to be getting lost at C3 or R3.

I built it and it has unity volume with no mods.

I haven't tried with the wrong value pots but I am reasonably certain it will still work OK. By all means change them but I don't think that is the problem. Do you get audio going in to pin 1 of the FV-1, and it it coming out at pin 28?