WiiM Pro optical ground loop

U

ummduh

Member
Joined
May 20, 2025
Messages
11
Lately, I've been getting a pretty bad ground loop hum. It wasn't there when new, I've had this about 6 months now.

I exclusively listen to this via Chromecast to my old Yamaha home entertainment receiver.

All of a sudden it developed a pretty gnarly ground loop hum when I turn the receiver on, until the Chromecast connection happens. Once it's connected to Chromecast the hum completely goes away until I disconnect.

I have to connect with Chromecast, and then press play, and as soon as I press play the hum goes away completely.

I dont have other circuits to try, I have a single circuit serving my garage.

It is plugged in to a multi plug adapter deal (not a surge strip). But like I said, this developed quite a while after initial installation. I haven't changed anything.

Any ideas?
 
Welcome.

So the only connections into the Yamaha are the mains and the optical from the pro?
Does the yamaha start on a different input and auto switch to the optical when you play to the pro?
 
You should switch out the optical cable and start there. Put in a nice glass toslink cable. They are not expensive these days.
 
Mr Ee said:
Welcome.

So the only connections into the Yamaha are the mains and the optical from the pro?
Does the yamaha start on a different input and auto switch to the optical when you play to the pro?
Click to expand...

Correct, only an optical cable, and besides power, optical is also the only connection on the WiiM.

No, the reciver stays on "optical in" at all times.

The WiiM replaced the original chromecast audio that google bricked a while back, its the only thing on the receiver. Never had a hum with the cc-a (and it was on there for a LONG time)
 
ummduh said:
Correct, only an optical cable, and besides power, optical is also the only connection on the WiiM.

No, the reciver stays on "optical in" at all times.

The WiiM replaced the original chromecast audio that google bricked a while back, its the only thing on the receiver. Never had a hum with the cc-a (and it was on there for a LONG time)
Click to expand...
You should report back to wiim using the more,feedback section on the app. They could have a look at your device logs and perhaps offer a solution or replacement.
Ps. I think the chromecast pucks are fixed now 👍
 
ummduh said:
It is plugged in to a multi plug adapter deal (not a surge strip). But like I said, this developed quite a while after initial installation. I haven't changed anything.

Any ideas?
Click to expand...

What is that multi plug adapter deal? Have you tried something that would rule it out as the issue?
 
Yeah, if the WiiM is connected via optical it's not that connection. You need to look at where the components are electrically connected and that sounds like that plug adapter. Maybe swap it out?

The noise goes away when you take the power out of the WiiM?
 
waldo said:
What is that multi plug adapter deal? Have you tried something that would rule it out as the issue?
Click to expand...

It's just a construction site style extension cord with a multi plug connector built into it, not a surge strip.

The receiver, the sub, and the WiiM are plugged into it. Sub is also a Yamaha. I've unplugged everything not audio related from the other side of the outlet with no change.

Something else I just learned: if I disconnect the WiiM from Chromecast the hum does not immediately come back. I'm not sure how long it has to sit disconnected before it comes back. I assume it goes into some kind of sleep/power save at some point
I'll swap out the power block at some point tonight and see if it does anything for next time.
 
Last edited:
Ronnie D said:
You should report back to wiim using the more,feedback section on the app. They could have a look at your device logs and perhaps offer a solution or replacement.
Ps. I think the chromecast pucks are fixed now 👍
Click to expand...

Done.

I ended up with the WiiM because nobody knew how long they'd be down. And now I have the WiiM so no reason to go back, but I should probably power it up and let it update.
 
A subwoofer!

Where's that plugged into is it the same outlet as the rest of the Hi-Fi gear or a different one. Take it out of the loop by unplugging from the electricity and signal.
 
freaknout said:
A subwoofer!

Where's that plugged into is it the same outlet as the rest of the Hi-Fi gear or a different one. Take it out of the loop by unplugging from the electricity and signal.
Click to expand...

I only have one circuit (in my garage) so yes, it's on the same circuit. same plug. I will try that as well, but I'm gunna be pretty annoyed if that's it.

You'd sure hate to see all the other stuff running on that circuit. There's an air compressor, various grinders, a belt sander, a dehumidifier, a computer, a drill press, multiple battery chargers... Obviously it's not all used at the same time.

I did unplug all that other stuff and it made no difference. I have not unplugged the sub. Between that and the power adapter, I'll try that and report back in a couple days.
 
The important thing is that the hifi ties back to one ground, not necessarily the other stuff in the circuit.
 
Don't forget the signal cable to the sub. They can easily create ground loops and more expensive sub cables usually have a grounding lead on them.
 
freaknout said:
Don't forget the signal cable to the sub. They can easily create ground loops and more expensive sub cables usually have a grounding lead on them.
Click to expand...
I guess I should have said I know car audio. I'm not a home audio equipment guy.

The sub is active and the audio cable is just a single rca and I'd assume pre-amp voltages. I've never actually checked or given it a single thought though.

I'll add it to the list, I guess this is probably going to be a few days of ruling things out.
 
Well of course, I get home from work and fire up the garage stereo and today there's no hum at all. I didn't touch anything yet. :rolleyes:

First time it hasn't hummed in several weeks
 
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