TOPIC: Ground Loop Hum SHD

Received my miniDSP SHD and happily integrated it into the system. Like the sound and functions.
Shocked to find that it forms ground loop hum in my system when TV ON.

Floating either SHD or TV’s ground pin, the hum is gone.
TV-HDMI-AVR-Power AMP
SHD-Power AMP

SHD Mute vs On vs OFF makes no difference in the ground loop hum I heard.
SHD is used for streaming with no other input connected to it.

It only requires following to trigger the ground loop hum

SHD XLR connection to the power amp
SHD Power cable to socket (Doesn’t matter ON/OFF/Mute)
TV HDMI to AVR to power amp
TV turned ON

Is this a known issue that I should send for an exchange? I cannot afford to replace my TV which served us well for a few years.

Is there an audio connection between your TV and SHD, and if so what type? A Toslink connection may solve the issue?

Changing where the TV and SHD are plugged in may also help.

There is no audio connection from TV to the SHD. TV is connected via HDMI to the receiver. The receiver and SHD share the same power amp, power socket.

SHD-> Power Amp
AVR-> TV/Power Amp

Tried plug the SHD and TV on to the same distributor, didn’t help

yakman wrote:
How are you switching between SHD and AVR connections to your power amp?

SHD XLR to Power AMP XLR input
AVR RCA to Power AMP RCA input

I don't recall any other SHD users having ground loop hum problems so it's probably an issue with your 'system' or less likely a fault in the SHD.

XLR connections are balanced and should usually have the screen disconnected at the source to break ground loops. If that is already the case and the SHD causes ground loop hum with nothing else connected to the SHD it could be a fault in the SHD.

yakman wrote:
Does your power amp have a way of switching between the two input types, or are both active simultaneously? I suspect this is the source of your issue. Does your power amp have any different grounding options? Just asking as on mine I have the option to switch to a floating ground if there are issues like you're having with RCA inputs.

(My power amp has both RCA and XLR inputs but I'm sure only one or the other is ever intended to be connected at once.)

Does it make a difference if you mute the SHD?

My power amp has a switch for each channel for XLR/RCA input selection.
SHD does not need to be ON. It only needs the XLR connect to Power AMP and power cable to power switch.
TV has to be ON, with HDMI connected to the AVR.
The ground loop hum volume level is not dependent on the SHD volume, but the HDMI switching on the TV seems to add to that.

yakman wrote:
I wouldn't expect the SHD volume setting to make an difference but being muted might. (In my system I get audible background hum/hiss from my speakers if the output is muted but not if the SHD is on but notmuted, so I think something is being actively changed rather than just gain.)

I can't follow from what you've written above if you get the same issue if the SHD is switched off as when it is switched on?

What power amp do you have out of interest?

SHD Mute vs On vs OFF makes no difference in the ground loop hum I heard.
SHD is used for streaming with no other input connected to it.

It only requires following to trigger the ground loop hum

SHD XLR connection to the power amp
SHD Power cable to socket (Doesn’t matter ON/OFF/Mute)
TV HDMI to AVR to power amp
TV turned ON

My power amp is Emotiva XPA3 Gen 2

If removing the SHD XLR connection to the power amp solves the ground loop hum problem it can probably be properly solved by disconnecting pin 1 at the SHD end of the XLR cable.

Ground loops are common problems and not usually a problem in any piece of hardware but rather in the connections between them. It is far easier to solve properly in balanced connections.