[winter_syn]

I need some help with the hum that is coming through my speakers.

I original setup:

PC (Phantom Canyon NUC) -> USB (Supra Excaliber) -> DAC (Chord Qutest) -> RCA (Chord Clearway) -> HP amp (ifi Zen Can Signature 6XX) -> Balanced cable (custom 4.4mm to two 6.35mm jacks) -> Powered monitors (Presonus Eris E4.5)

This worked perfectly fine and there was no hum on the speakers, but I wanted to move the Qutest to connect it to my ifi Zen Stream because I'm setting up a Roon server and want my best dac on that. So I purchased an ifi Zen Dac Signature v2 as I only use USB with the PC and thought it would be a good pairing with the Zen Can.

After the Zen Dac arrived, I unplugged the Qutest and plugged in the Zen Dac. The last cable I connected was the USB and as soon as I did I started getting a loud hum out of the speakers, this happened both with and without the separate power cable connected to the dac. I put the Qutest back in and the hum vanished. I then grabbed my Topping D10 from another rig and put that in and the hum returned.

This starting making me thing it may be a ground loop problem, so I started hunting around in my hifi bits draw to see if I had anything that could help. I didn't have much, but thought it would be worth trying so I tried putting an AudioQuest Jitterbug in between the PC and the USB cable but that made no difference, I then tried an ifi iSilencer+ and that made no difference. I swapped out the RCA's for a 4.4mm to 4.4mm balance cable between the Zen Dac and the Zen Can and that didn't help.

Plugging in headphones to the Zen Can and I can hear it, but if I turn off the monitors the hum seems to vanish and I need to crank up the volume on the amp all the way to even start hearing something. Also the hum on the monitors increase with the volume increasing.

Is this sounding like a ground loop issue? If so does anyone have a suggestion on what to do to resolve this? Was thinking about getting something like the ifi Dc blocker or the GRD Defender to put between the mains and the monitors but the E4.5 uses a figure 8 mains connector, I could get something like the Clearer Audio Solid IEC to Figure 8 Adaptor (https://www.futureshop.co.uk/clearer-audio-solid-iec-to-figure-8-adaptor), but not sure if this will work.

 

[Alcophone]

It might be useful to know what is plugged into what, power wise (outlets, power strips) and whether your electricity is generally up to snuff (do you have a receptacle tester?).

Anyway, I recently tested a scenario where active Logitech speakers were plugged into an Echo Dot (3.5mm TRS), and both the speakers and the Echo Dot were powered by the same USB power supply (with multiple ports). Hilariously noisy.

Putting the speakers into a second USB power supply fixes it, but that's boring. Continuing to use the same power supply as the Echo Dot, but with an Intona High Speed USB isolator inbetween also fixes it even without using its aux power input (expensive, but impressive). An iFi iDefender with separate external power supply also fixes it. An iFi iDefender without external power reduces the noise significantly, but not sufficiently (did not expect this to do anything, actually). Powered USB hubs were useless (I think they don't cut ground to the host, unlike the iFi iDefender). An iFi iSilencer didn't do anything (I suspect that one only handles noise on the data lines and is useless for USB power noise).

 

[winter_syn]

They are all plugged into the same extension block, a Tacima CS947. I do have a couple of other, surge protested, extension blocks nearby but none are in use for my audio equipment. The mains into the house is normally pretty good, don't generally get any surges or power cuts, but not really in a position to check unfortunately. Mains supply in UK cities is normally pretty good and the house wiring was updated when we had a new modern fuse box fitted in the 90's, so it should be complying with UK standards.

I forgot I had a shiit Wyrd in my other rig, so stuck that in, tried it on the Tacima block and on one of my other extensions (so connection to a different power point) and that didn't help.

 

[Alcophone]

Something like this is what I had in mind:
https://www.amazon.co.uk/Reenwee-Receptacle-Analyzer-Electricity-Indications/dp/B091TM5TD1/



I paid $4.49 for my Klein Tools RT100, maybe you'll find something similarly cheap, but the above one is certainly more capable. But chances are everything is fine anyway.

Do you get a hum with your phone is the source? Can you try with a laptop (with and without a charger)?

I'd also try re-seating the cables into the speakers, anything like TS/TRS can easily cause a short somewhere when not plugged in right (you've probably thought of that, but just in case...). Also would try using regular RCA cables into the speakers, maybe rotate the power cable into the speakers (since it's not polarized). You could also bypass the ZEN CAN for testing, just make sure to use software volume control or mute, shouldn't need a signal to buzz.

Basically just poke at the system until something unexpected happens, hehe.