[SAURUS]

I built this circuit but it doesn't seem to work the way I expected it to. When I switch it into the feedback loop mode it doesn't oscillate the pedals into oblivion?! The 500k pot seems to work as a volume instead of controlling the amount of oscillation. I am pretty confident I built it correctly and upon checking back to the site I discovered that others had reported similar issues. Is there an issue within this design or am I missing something?

 

[High/Deaf]

I think you are defining 'feedback' different than the designer.

This 'pedal' has no gain stage, so I don't know how it could create any oscillations of it's own. Without looking to far into the signal path, I'm guessing the 'feedback' pot is more like a mix pot, mixing more or less signal into the send jack. If you have a high gain pedal or a delay set to oscillate in the 'send/return' path, I can see how that pot might control the amount of feedback via the outboard effect. Other than that, I think it's just a terminology problem - something endemic in the guitar world.

 

[Granny Gremlin]

I don't think the OP was expecting this passive looper pedal to self-oscilate.

The feedback here is more of a foldback. Like back in the day when a delay was a single repeat, you would have to feed the delay output back into the input to generate multiple repeats (now delay pedals/rack units, have this pre-wired for you with a knob).

So you can get more distortion on your distortion with this thing, and yes, you should be able to generate actual feedback by making the pedals in the loop oscillate at more extreme feedback knob settings, but not all pedals will react that way. What pedals do you have in the loop? If you have a basic analog delay, try running just that and see if you can get it to oscillate when you crank the feedback knob. If it does then you're good and there was probably some pedal in the loop chain that was softenning things up. If not, try the following.

To test that it's wired up right as regards the feedback part of the circuit:
- make sure there is nothing plugged into either the input or send jacks.
- plug a sound source into the return jack (ipod etc)
- engage feedback switch
- turn up the feedback knob all the way
- plug the send jack into an amp (if you used an ipod, just headphones will do - only on tyhe left vs both, but that's fine for this test) - got signal? If so the looper is working as it should
- If no signal turn the feedback knob all the way the other way
- got signal? If so the feedback knob is wired backwards - know that and leave it that way or switch the wires from terminals 1 and 3 on the feedback pot
- if no sound either way there is a more involved issue I can't troubleshoot online like this. (try also flipping the feedback switch to off and repeating the above)

Diagram looks fine from my quick check.

 

[mhammer]

It's one of John Lyons' diagrams, which - if they are still posted - are 99.9% likely to be correct.

The assumption inherent to such loops is that the pedal IN the loop will have gain and a higher-amplitude output than input. This is why the unit has a pot for feedback. It doesn't add anything. Rather it takes away as much as you need to take away to get the whole assembly to behave in a musically useful way.

Perhaps a silly question that underestimates your chops, but....you realize that the 3PDT switch, as shown, switches in the vertical direction, and not the horizontal direction? So, looking at the far left of that switch, the "blue" lug gets switched between "red" and "black".

You wouldn't be the first person in history to misinterpret the direction of either such a diagram or the actual wiring of lugs on the switch. When it's a DPDT, having 3 lugs in one direction and 2 in the other, makes it pretty obvious what direction things go in. When the switch is a 3 x 3 matrix, it's a lot easier to mistaken misorient connections.

The other thing to consider is that you might have overheated one or more of the stompswitch lugs during the building and caused the grease inside to liquefy, flow along the contact, and act as an unintentional insulator. As always, I refer you to this:

 

[SAURUS]

I should mention that I built 5 of them and they all have the same issue, I didn't melt any switches and they all work while in the normal effect loop mode.
I have a Hotone Eko delay and a distortion in my loop. The distortion squeals a bit when the pot is turned from 0- 1/2 way and the delay doesn't change at all.
I found this in the comment section of the blog that had the schematic:

"Is there an error in this schematic? I get the pot turning the signal off when in bypass and turned to zero. Looking at it appears that output is connected to send through the pot, but send is grounded in bypass. So its not true bypass, the pot is acting like a volume control to ground! Connect the output to the 3pdt switch only, and instead wire the RETURN to the spdt switch, which makes a lot more sense, you only need the feedback on the return anyway, i'm not entirely sure why output was chosen at all."

Do you agree with this guys logic? I tried doing what he said and it didn't work but if I hold my fingers against the send jack and the spdt I can get it to oscillate like it should. I'll try and fart around with them a bit more when I get back home from the cottage. If it doesn't work out I'll upload some photos or videos to make it easier to diagnose.