trouble with EHX micro synthesizer

[dualaud]

hiya,

this is my first post, so hi to all!

i have an 'old style' guitar micro synthesizer (with internal power supply), and modded it like this: 3PDT switch for true bypass, the 3PDT allowed me to turn the power LED into a status LED and i turned the device into a bass micro synth version by changing three parts as told me by EHX.

the device works good except this one thing which startles me:
there is very much interference noise when i connect the device to my amp. having a palmer line isolation box (PLI-01) i decided to plug it behind  my micro synth, and gone is the interference...
but say hello to major POP...  

the pop only appears when switching the device OFF.
this dissappears when not using the line isolation box, but then the noise comes back in.
i already soldered a 1MOhm resistor from input to ground to get rid of the POP, but it didn’t help. so the problem is at the output side, i guess.

but as i held the resistor to the appropriate connections on the output side of the switch, it had no effect...
any thoughts on how to get rid of either the interference noise or the POP?
could it be that the LED was an important element in the devices circuit, and without it there is noise? dunno...
:cry:

any ideas are greatly appreciated,
dualaud

[niftydog]

missed this post originally, but I have some ideas for you.

When you say "interference" what does it sound like?

I'm thinking that you may have DC on the output signal. Have you checked this with a multimeter? With no guitar plugged in, measure the DC voltage at the output.

Otherwise, maybe a poor ground connection... but the isolation box results make me lean towards something else.