HT Bypass and Ground Loop Hum

Hey guys,
I'm trying to set up HT Bypass to combine my dedicated 2ch and combo HT/music systems, and eliminate a set of speakers from the space.

I'm using a Musical Fidelity A5 in the 2ch.
I'm using a Parasound HCA-2205 for the HT.

The first time I tried to set this up, I got hum at the two front speakers. I know it's due to the the cable tv feed from prior troubleshooting years ago wherein the hum would disappear if I disconnect the coax. Power comes in on one side of the house, cable on the other, each with their own ground rods. No getting around that.

When I first tried this a week ago, both the A5 and 2205 were originally connected to different power distribution units on different receptacles, but possibly on the same circuit. I thought that combining the A5's and Parasound's power sources on the high current bank of a PS Audio Dectet might help. It does not. I'm still getting GLH, but now it's switched to the center channel, powered by the Parasound 2205, which I don't quite understand at this point, but it's not of major concern at the moment. It's either the mains or the center that does it, which are each powered by different amps.

If I put a cheater plug on the Parasound's power cable, the hum goes away.

I don't like the idea of a cheater plug, and ordered a coax ground loop hum isolator to try to see if that helps.

Any of you had to combat this issue? How'd you get through it? Thoughts on use of a cheater plug or these coax GLH isolators?

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Comments

  • pitdogg2
    pitdogg2 Posts: 19,501
    edited September 25
    Can you tie both grounds together with some #4 or #6 solid copper?

    If not try removing the cable ground at the RCA end that connects to the gear. I've had to do that.
  • msg
    msg Posts: 6,699
    Good idea Ivan. They're on opposite ends of the house. I wouldnt be able to do it without a really long run around the back of the house or tunnelling under concrete.

    By removing the cable ground at the RCA end, are you talking about an interconnect into the amp?

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  • pitdogg2
    pitdogg2 Posts: 19,501
    edited September 25
    I assumed the hum was coming from the cable coax, while I said RCA I was really talking F-connector from the cable. You would need to re-terminate the cable. The ground is the shield SO instead of folding the shield back to catch the ground, you cut it off and terminate with no shield. So once again no mylar, no braided shield under the connector to pick up the ground, you are only after the wire that carries the cable signal.
  • pitdogg2
    pitdogg2 Posts: 19,501
    edited September 25
    msg wrote: »
    Good idea Ivan. They're on opposite ends of the house. I wouldnt be able to do it without a really long run around the back of the house or tunnelling under concrete.

    Dude seriously! What you should do is connect them over the top of your house and put a spire in the middle and then down the other side you needed a lightning arrester anyway right?

    😂🤣🤣
  • msg
    msg Posts: 6,699
    I'm pretty sure it is. I didn't try disconnecting it today, but last time I messed with this, disconnecting the coax stopped the hum.

    Okay, that's what I thought you meant. Just like with making RCA cables and terminating the shielding on the source side only?
    I disabled signatures.
  • pitdogg2
    pitdogg2 Posts: 19,501
    Okay, that's what I thought you meant. Just like with making RCA cables and terminating the shielding on the source side only?

    Yes!!