I had a similar issue with MORE and a BassDude with the Emma Discumbobulator v3 envelope filter.
When the MORE or Bassdude was placed before the Emma, there was an odd interaction that produced some squeeling. Even when using separate isolated power supplies on 2 different outlets. If I placed the MORE or Bassdude after the Emma, there was no issue.
The Emma is the only pedal that I've had this happen do, no issues when running those before an Iron Ether XD, Broughton Joshwah, or 3Leaf Proton.
I asked Nathan about it, and he was stumped. On their own they were great, no issues, but when placed before the Emma, squeel city. The Sushibox pedals weren't the issue, they play nicely in every other scenario.
I work in IT, and had an issue once where an HP printer didn't like a Cisco switch. Countless hours troubleshooting, replacement network card for the printer, switch worked fine with other devices on the same port. Finally put a dummy switch in between them and it started working. Some sort of incompatibility between the chipsets on each device. Some things just aren't meant to be explained.
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