Pladask Elektrisk Bandorg Delay - will only produce one repeat

[moid]

OK It seems that i could've got a lot weirder then Thanks for the suggestions Anotherjim.

Some good news! I finished the pedal and it works My first finished and functioning pedal in two years (what a sad statement that is...). A lot of extra changes were made across the weekend, mostly for the better (I am now a huge fan of attaching random pot lugs to a low value resistor and then connecting that to ground). My only mistake was making a pot out of a trimmer that at one point modfied how long it took for feedback to fade in, but I must've got keen on changing something else and didn't test that function - it still slightly works but is not worth the effort of it being there... but the box is such a nightmare to assemble that I'm not making any changes in case I break the mojo / various cables and dodgy bits of insulation tape). Anyway my son said he is happy to record a demo of it, so watch this space! The pedal sounds great - lots of lo fi echo tones to be had, plus some impressive fuzz sounds, a little near ring mod feature and all the oscillating feedback you could desire!

[moid]

Well it's eating my words time of course... I've since discovered that this pedal does not behave itself when connected to any other pedals, even if they share different power sources. The really cool sounds I made from connecting some of the lug 1's on some pots via resistors to ground, are, I expect, to blame. On it's own I can get some really interesting sounds, but when connected to other pedals the circuit works, but only at a very basic level and there are none of extra cool sounds that I like. Sooo, big question time... is there any way to somehow isolate those ground connections so that the pedal could work as intended with other pedals? At the moment those extra ground connections go to the ground lug on one of the audio jacks, or to the ground of the power jack. I know I need to draw a schematic to help, and I'll need to take the PCB out of its box somehow to do this, but is there a way to allow part of a circuit to go to ground that is not shared with anything else? I kind of have a vision of a strip of copper or aluminium that these extra connections attach to and then have that metal wrapped in insulation tape so it can't touch the enclosure or any of the circuit. Is this a daft idea? If it's a good idea, how large does this piece of metal need to be? Thanks for your thoughts.

[anotherjim]

I suspect a lot of circuit bending practices only succeed because the victim is usually some poor defenseless battery powered toy that lives on its own.

You might get away with making the delays ground virtual, but I suspect that will bring its own problems. It would definitely need its own isolated power supply and the 9v split so that the jack grounds are at the +4.5v split point and the circuit ground then left to float at -4.5v below the split. Actually, as there is a 5v regulator, then the +5v could be connector ground - the split doesn't have to be equal.

Otherwise, you could isolate the input and output with audio transformers.

[moid]

I'm sure you're right about the circuit bending... it's certainly been something I've found when I customize something to make a weird noise, that the weird noise is not so cool as soon as you plug the device into any other pedal

Hmmm isolating the input / output jacks with transformers sounds easier (to my amateur ears anyway!). I did some reading about transformers that can do what I want and I think I should look for a 600:600 ohm type (doesn't change sound volume or impedance at all) Does that sounds correct? I've never used a transformer before, but if this works it sounds like it could fix an issue with a couple of other pedal designs I have abused... Presumably I need one for the input and one for the output jacks? Quite how I will get them in the enclosure is another story...

Does this one look OK? Bourns LM-NP-1001-B1L https://www.bitsbox.co.uk/data/transformers/LMNPLP-42750.pdf I can get hold of those fairly easily, and they don't look too massive... but I don't know if they will fit into the rather snug space inside the box. If you happen to know of a smaller one please say so.

Thanks for the suggestions, they're greatly appreciated.

Hmmmm I guess if I can't fit them in the box itself I could make an additional small enclosure with four audio jacks - two for sound in, two for sound out, with the transformers inside so I could connect this to the delay pedal and any other pedal around it? Would it require power? It looks to me that it wouldn't because I'm not changing the audio signal... I think?

[anotherjim]

Those transformers will probably be ok.

They are rated as Modem isolators. That only requires telecom voice frequency response, 300Hz to 3.3kHz, but as we're not in Kansas anymore, that might actually be for the best However, bear that in mind if you make them up as a general-purpose ground isolator.
According to the datasheet, they are full response 200Hz to 3.5Khz with some useful response up to 10Khz.

The primary impedance of 600ohm won't work well driven by passive guitars, so you will want an active pedal of some kind with a buffered bypass (any Boss stompbox for example) or if true bypass then the effect must be active.