Increased noise floor when running thru PBC...

I’m having the same issue with a PBC10. only with high gain amps. Lower gain plexi style, zero noise if any.
I have isolated every way possible and can’t get rid of it.
I have another board with a PBC6 that doesn’t make noise.
 
Follow up, I went around the front end loops (1-6j), with high gain amps I don’t use them anyway.
7-10 with stereo effects no noise, I can live with this.
 
After struggling with an elevated noise floor on my PBC10 for a while, I finally figured out that the hissing gets introduced between In 5-6 and Out 5-6. I've tried a Lehle P-split in various locations without any success. Turning the internal buffers ON doesn't seem to help. It sounds more like hissing than an actual ground loop hum.

No noise when In1-4 -> Out1-4 -> In7-10 -> A&B (skip loops 5 & 6)
No noise if In7-10 -> A&B (skip loops 1-6)
Noise when In1-4 -> Out5-6 (skip loops 7-10)
Noise when In5-6 -> A&B

Anything I could try?
 
In the tests resulting in noise, is anything connected to In 5-6 and Out 5-6? And, is anything in loops 5&6?
 
rjmmusic said:
In the tests resulting in noise, is anything connected to In 5-6 and Out 5-6? And, is anything in loops 5&6?
Click to expand...

Thanks for reaching out. I just did another bunch of tests and the problem seems to be tied to Out5-6 and loop 5 send.

no noise when connecting:
loop5 return -> loop6 send
In5-6 -> loop6 send
In1-4 -> Out1-4

noise when connecting:
In5-6 -> Out5-6 (with or without pedals connected in loops 5&6)
In5-6 -> loop5 send
loop6 return -> Out5-6

I've only powered the PBC10 for these tests. All other stuff on the board was without power or grounding. Amp and PSU on same power source.
What is weird is the inconsistency of the noise. It's sometimes worse. But it's always tied to what happens between In5-6 and Out5-6
 
moehuh said:
Thanks for reaching out. I just did another bunch of tests and the problem seems to be tied to Out5-6 and loop 5 send.

no noise when connecting:
loop5 return -> loop6 send
In5-6 -> loop6 send
In1-4 -> Out1-4

noise when connecting:
In5-6 -> Out5-6 (with or without pedals connected in loops 5&6)
In5-6 -> loop5 send
loop6 return -> Out5-6

I've only powered the PBC10 for these tests. All other stuff on the board was without power or grounding. Amp and PSU on same power source.
What is weird is the inconsistency of the noise. It's sometimes worse. But it's always tied to what happens between In5-6 and Out5-6
Click to expand...

Are these actually the way you wired the system, or are they typos? If you wire the system either of those two ways, it wouldn't pass audio. The first one has two cables connected to loop 6 send, as well.
 
rjmmusic said:
Are these actually the way you wired the system, or are they typos? If you wire the system either of those two ways, it wouldn't pass audio. The first one has two cables connected to loop 6 send, as well.
Click to expand...

Sorry I did not write it in a clear way. Let me try again :)

no noise when connecting:
Guitar into return 5 -> send 6 to amp (loop 5&6 ON)
Guitar into In5-6 -> send 6 to amp (loop 6 ON)
Guitar into In1-4 -> Out1-4 to amp

noise when connecting:
Guitar into In5-6 -> Out5-6 (with or without pedals connected in loops 5&6) to amp
Guitar into In5-6 -> send 5 to amp (loop 5 ON)
Guitar into return 6 -> Out5-6 to amp (loop 6 ON)
 
I found that having a Lehle buffer (Sunday Driver II) between Out1-4 and In5-6 seems to help a bit with the noise. But it's weird that the internal buffer #1 wouldn't help. Also having the same buffer in front of the PBC doesn't help. There is something strange between In5-6 and Out5-6
 
It sounds like there may be a problem with the relay that controls loop 6 (or possibly loop 5). Either there's a bad connection in there or one or two of the relays need to be replaced.
 
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