aclac
Active member
HI, I am new here... finished REV.J 1176 project couple days ago. Two comp. unit inside 2U metalbox with M.Nats PSU. It seem to work well, but... hum is totally LOUD expecially, when I unplug input XLR connectors from mixer (even -20 dB). When I have XLR conneced input, this hum is not so bad, but I can't live with it. I had 2 VU lamps (8V, 50mA) connected with 270 ohm serial resistor in the 30VDC rail, but it gave more hum to circuit and I loose them of... SAD, because I'd like them back. I think, that this hum is caming through PSU, but I don't know how I test it? I tried to take power transformer (toroidal) 24-0-24 VAC (90VA) out from box, but it was not the main hum reason. The XLR- input pin 1 is grounded and so is power transformers center tip... and main supply's ground wire. The wires inside the box was made like instrustions said, and... rotary switch cables are not twisted as the instructions, is this OK? As I though, that hum sounds like 50 Hz transformer... and I can't measure and eliminate it. Don't KnowHow? This project was very interesting and I'd like thank everybody here, because I was get lot of information here and without you I maybe could't start this project. Please, help me with this problem, I tried get solution here and everywhere, but not got yet. I can give sound sample or foto of my project, if this help you? Thanks...