388 Stereo Buss Inputs are Noisy

M

Mark7

Well-known member
When I plug a pair of RCA jacks into them I can hear what sounds like pink noise(?) that doesn't disappear until I remove the jacks.

Any ideas?
 
So the unbalanced 1/4' are going to a patch bay- unterminated- as in antenna? What happens when you disconnect from the patchbay first, 2nd test. when you short the cable going to the buss input with a low value- say 100 ohm resistor?
 
I don't have a 100 ohm resistor.

Don't know what you mean by antenna in this case.

I tried unplugging at the patchbay end. The sound was still there. It's like a continuous bizzing (not a "buzzing). It seemed to be at a lower level than I remembered it being yesterday. But, then again, for some reason my mic wasn't working today either, whereas yesterday it was.

No, Wait. I just realised why I wasn't getting any signal from the mic. I was using the wrong bleeding channel on the mixer :o
 
Unterminated inputs are always going to be noisier than terminated (i.e. plugged into something active, like, not just a patchbay. And the 1/4” plugs at the patchbay...are they TRS or TS? Is the cable single conductor with shield/ground Or two conductor with shield/ground? If it’s a balanced patchbay are the grounds bussed at the patchbay? What happens if you bypass the patchbay and actually have the buss inputs actually connected to another device? Do you still have the noise issue?
 
I meant "antenna" as a un-terminated cable that acting like an antenna. Pull the cable from the patchbay and short the tip to sleeve with a wire/needle nose pliers etc. Noise goes away? What else is connected to the patchbay?
 
All the access send and receive jacks, the aux and effect sends, the effect returns, the stereo buss outs, a Zoom 1201, Alesis 3630, KAM KEQ 15, Etek Dynamagic and Behringer Dualfex Pro. The KAM, Etek and Behringer all have balanced ins and outs. The Zoom and Alesis don't.
 
The only balanced I/O on the 388 is the mic inputs and the stereo buss outputs- all on XLR connectors. Everything else is unbalanced.
 
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