Hum hum hum

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.

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

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
 

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 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

Based on the comments so far, the problem is in the preamp (which is to say the cables and amp ar off the hook), but its unclear whether its a problem with a functioning source connected, as Al is asking about.

Since its affected by volume, its ahead of the volume control. The thing is, without an input, this could be perfectly normal. So connect something to the input and see if it still does it.

nimbus109,
As you can see, there are many way to interpret what you have said. Please be as detailed and descriptive as you can to insure you are understood, with not miscues. 

Disconnected all inputs and I get a distinct hum at high levels on one speaker with just the amp/preamp/speaker connection....  I probably will never play at these levels

I think you are saying that the hum occurs at high settings of the volume control, and varies with the setting of the volume control.  Correct?

When I switch xlr cables, the hum goes to the other speaker.

When you say "switch xlr cables" do you mean that both ends of each cable are moved from one channel to the other?  Or that just one end of the two cables is switched between channels?

Disconnected all inputs and I get a distinct hum at high levels on one speaker with just the amp/preamp/speaker connection.

Does the hum still occur when a powered up source component is connected to the preamp, and that component is selected by the preamp's input select switch?

Also, assuming that the preamp and amp have 3-prong power plugs it may be informative to temporarily try a cheater plug (a 3-prong to 2-prong adapter, with the safety ground left unconnected) on the power plug of one of those components.

Regards,
-- Al
 

When I switch xlr cables, the hum goes to the other speaker. I bought new xlr cables and same thing happens. 

What exactly do you mean by switching cables, and hum goes to the other one?

Does this mean the hum is going from one side to the other? If so, bad cables. :)

E