If you have no inputs connected to the pre you will most lokely pickup noise or hum. If you use a shorting cap does the hum go away. If you connect a device to the input of the pre is there still hum? If not there is no problem
Alan
Alan
Hum hum hum
I have connected my NOS PS Audio gca 250 to my PS audio pre. Disconnected all inputs and I get a distinct hum at high levels on one speaker with just the amp/preamp/speaker connection. . Swich the xlr cables and the hum goes to the other cable. I probably will never play at these levels, but I would like to trace and fix the hum. Any ideas? Thanks.
- ...
- 10 posts total
Sorry I have not been clear. With nothing connected to the preamp, I merely switched the xlr cables at the preamp end. Should I have switched them at the amp end as well? What are shorting caps? I was getting hum on one channel when I had cd and turntable connected and turning up volume with nothing playing the hum would gradually increase at higher settings |
If you search at eBay for "RCA shorting plugs" you'll find many examples, although I'm not aware of any that are readily available for XLR inputs. The point to assessing the hum with shorted inputs (i.e., with a connection between the center pin and the ground sleeve of an RCA input connector) is that the typically high impedance of unconnected inputs makes them susceptible to pickup of hum or noise even if everything is working properly. However, since you've found that the hum is present with two different source components connected there's probably no point to trying shorting plugs. And since the problem is sensitive to the position of the volume control the XLR cables and the amp are ruled out as suspects, as Ralph (Atmasphere) indicated. So everything seems to point to the problem being in the preamp. Assuming, that is, that the symptoms when the cd player is selected are essentially identical to when the phono source is selected. Regards, -- Al |
almarg If you search at eBay for "RCA shorting plugs" you'll find many examples, although I'm not aware of any that are readily available for XLR inputs.Cardas makes XLR plugs. They're non-shorting. http://www.cardas.com/protective_caps.php |
https://www.musicdirect.com/equipment/cardas-cgsp-xlr-shorting-strap-ea When xlr and rca inputs share the same circuit, you need to short pins 1 & 3 of the xlr inputs to avoid noise thru the rca connection. But always check if the manufacturer recommends this. Since PS Audio components are fully balanced, I don't know if these are needed. |
- 10 posts total