My mixer is a Yamaha shown in post 65 on page 7. I must re-state. There is no phantom power being used. It's turned off on the mixer.

I'm sorry, I forgot you posted that info before. I did a quick search to see if I could find a schematic for that mixer online, but no luck. Double check all your XLR cables to ensure they are wired each end the same, pin for pin. Even experienced people can sometimes flip pin 1 and 2 if they aren't paying close attention.

I would be surprised if that mixer had a bargain basement type impedance pseudo balanced input. One thing you might check, is with nothing plugged into the mixer input, insert a a small jewelers screwdriver into an input socket, first pin 2, raise the gain a little and see if you have hum or buzz. repeat with pin 3, both should produce some noise.

Then, plug one of your XLR cables into the input and repeat the test between pin 2 and 3 on the XLR female on the end of the cable. Repeat the same test with all cables. All should yield the same result of noise on pin 2 and 3.

Alternatively, you could meter the cables with an ohm meter, measure pin 1 on the XLR female to pin 1 on the XLR male. It should read very close to 0 ohms. Double check the numbers on the connectors to ensure you are measuring the correct pins. Also check for leakage or shorts between the pins, measuring between pin 1 to 2, pin 1 to 3, and finally pin 2 to 3. All should read infinitely high resistance.

As a side note: If you soldered these cables yourself, also ensure the shell terminal on the xlr connectors is left floating. There's seldom any need to connect it to pin 1.

I am sure this might be going too far on this but there is a link that will get you the full schematic for the PA in question...

[[url=http://[/URL]="http://elektrotanya…"]YAMAHA EMX62M Service Manual free download, schematics, eeprom, repair info for electronics[/]="http://elektrotanya…"]YAMAHA EMX62M Service Manual free download, schematics, eeprom, repair info for electronics[/]

There is a lot of info in this service manual... Here Byacey look into the schematic to check the input structure, just scroll down and click>>>

"This file is downloadable free of charge from the site: Get Manual" Click the "Get Manual" for a free download...smoke

Thanks for the link.
I had a quick look, and it's a fully balanced input, so there's no problem there. I'm thinking it's a mis wired connector or an error made somewhere in building up the switch box.