60hz buzz when FP410 connected to AC power

60hz buzz when FP410 connected to AC power

Date Updated: March 2, 2018 FAQ #441
Question:
Model # FP410Output mic-level (either output) to a Digital camera (Canon Optura Pi)When I plug in the AC line cord to the mixer, I get a 60hz buzz. I have a set of headphones plugged into the camera for monitoring.If I JUST BARELY plug the FP410 AC line cord in, more specifically, just have the ground pin touch the ground lug in the AC outlet (with no AC-power contacted), I get a nasty buzzing through the headphones.If I unplug the AC line cord, (running on battery) the buzz goes completely away.Also, if I have the FP410 on AC, but unplug the AC->DC-converted power from the camera (run IT on battery), the buzz disappears.Am I getting a ground-loop here?Both AC line cords are plugged into the same duplex outlet/circuit.I have a "homemade" XLR->1/8" cable running from the mixer to the camera. Would this be the culprit, and if so, what would the schematic look like for a "good" cable? this one I just tied ?the correct? pins together. I have seen a schematic for one that had resistors/etc in the circuit.Any help would be appreciated. We have a show coming up next week we will need to use this equipment heavily for.
Answer:


Here are answers to your questions.
Am I getting a ground-loop here? Yes.
Would this be the culprit, and if so, what would the schematic look like for a "good" cable? Use a cable with two inner conductors and a shield. Inner conductor #1: XLR pin 2 to 1/8" plug TIP. Inner conductor #2: XLR pin 3 to 1/8" plug SLEEVE. Shield: XLR pin 1 and no connection at the 1/8" plug.
If this does not solve the problem, then you will need a balancing transformer at the input of the camera.