Made system changes, now have ground loop hum?

[nicktf]

Guys, my system consists of 7 speakers powered by a pioneer 1015 Tx reciever, a QSC PLX 3602 pro amp which powered my DIY subwoofer system, and a velodyne sms1 to eq the sub. Now i've recently sold the diy sub to implement an infinite baffle system. In the mean time i've switched my QSC pro amp to powering my main speakers. Obviously the sms1 is out of the system for the time being. I've had cable ground loop problems in the past and eliminated those problems with a piece from parts express which goes between the cable outlet and the line.

Now since i've switched the QSC amp to power the mains and removed the sms1 I now have ground loop hum again.

Any suggestions on things to check?

My system is and has always been powered by 3 separate 20 amp circuits that were wired just for my audio equipment during construction of my house (new construction). I did not change up anything and my reciever remains on one of the circuits, the QSC pro amp on another, and the remainder of my stuff on the third 20 amp circuit.

Just to reitterate I was able to eliminate the ground loop problem before. What would cause it to return?

[ThomasW]

Anytime any changes are made to a system it opens up the possibility of a ground loop being created.

I've never had any success with anything other than balanced power devices and a mix of cheater plugs.

[nicktf]

admin said:

Anytime any changes are made to a system it opens up the possibility of a ground loop being created.

I've never had any success with anything other than balanced power devices and a mix of cheater plugs.

Thomas, where can I find cheater plugs? I understand what they are just need to know where to find them.

When you say balanced do you refer to something along the lines of my amplifiers balanced input or an actual power source? Reason I ask is that i'm using and unbalanced signal via just using rca to 1/4" trs jacks to route the signal to my QSC PLX 3602 amp.

[ThomasW]

I buy them at the local hardware store or in the electrical dept of any big box home center store. They're sometimes called 3 prong to 2 prong adaptors.

I was referring to balance power transformers like those from
www.equitech.com/

But using balanced interconnects certainly won't hurt either if there's a way to use them. Going from RCA to XLR doesn't create a balanced cable.

[nicktf]

It turns out it had nothing to do with the cable box this time around. It seems when removing and plugging back in the rca connections to my pro amp the hum goes and then comes back (comes back once hooked up). I'm guessing this means a cheater plug is needed for my pro amp which will eliminate it's ground?

[nicktf]

Cheater plug fixed my problems with hum

[ThomasW]

Good news...

[nicktf]

admin said:

Good news...

Yeah, that problem was very annoying. Only problem I have now is that I will have to go from 900x2 back to 110 x 2 on my mains when I get the IB in place . Oh well, not for long until an EP2500 with a modified fan will find itself in my system powering them. I doubt i'd be able to tell the difference between say 500 x 2 or 900 x 2 so hopefully that amp will give me all the headroom I or the BP20s can stand!