kwillisjr wrote:I think I may have discovered the root cause of our audio hum problem. I see that there was an XLR to 1/8" mini adapter included in the original communicator kit. I'm not sure what happened to it but I've never seen it. We (I) have been trying to adapt from an XLR line level output to what I thought was supposed to be a mono mini line level input. I see now that the adapter is XLR on one end and stereo mini on the other. I'm going to have to make an adapter for our system but I don't know the correct pin out from the XLR to the mini stereo connector. Can somebody enlighten me?
Thanks,
Ken
Based on other postings in the thread and what I have gathered from my STS, the communicator appears to take stereo line-level input. The feed from the PA system is almost certainly balanced mono. While you could do that conversion with a resistor network (basically by ignoring one side of PA's feed), I would recommend a 1:1 audio isolation transformer, such as Radio Shack's 273-1374 (assuming it's still sold).
I would connect the transformer primary to the two signal wires from the PA's feed. Connect one wire from the transformer secondary to the signal lines of
both the L and R (tip and ring) of the cable to the communicator. Connect the other wire from the transformer secondary to ground/return (sleeve) of the cable to the communicator. Depending on which gives less hum, connect or don't connect the ground/sheild from the PA's feed to the ground/return/sleeve of the cable to the communicator. (IIUC, that's what the hum switch does on the "crab" box.) If the verbal wiring diagram isn't clear, I could draw up a schematic.
Depending on signal levels, you might want some resistors to attenuate the signal. Better yet, after the transformer, run the signal to the communicator through a small mixer or a decent audio cassette deck from a thrift store--anything to give you manual gain control and a level meter.
