I’m having 60hz speaker hum which I’ve tracked to my DAC. But before I do something expensive, its been suggested that I swap out cables. Problem is, I don’t have any spares which would qualify as a “good solution”.
Need a mid-range supplier for a short BNC and a 3ft RCA. To give you an idea of the equipment quality, they’re going in to and out of a Yggy, a DigiOne, and an MRX720 powering wired Paradigm speakers.
Many thanks in advance for your thoughts and recs. John
Jeff, I have balanced out of Yggy, but not into the 720. So it’s gotta stay RCA in the short run, although I can switch to the second set of RCA outputs.
BTW, I know nothing about speaker noise types, but I went to some Info-ad website, and my sound matched up with a track they call “mechanical hum”. “Ground loop” sounded more like a buzz. Could be true or not.
Just to fill things out:
Sound becomes audible across the room at -28dB, up close at maybe -31dB
Hum is limited to one channel, Analog 2 coming from Yggy.
I changed the Roon path to use Oppo as endpoint, circumvent DigiOne and Yggy, into Analog 1. The sound ceased.
Back with the troubled path, I tried unplugging and plugging devices (other than the MRX). Unplugged DigiOne. No change. Switch Yggy OFF. No change. Unplugged Yggy. Hum stopped.
So I infer that the problem is with 720, Yggy, or interaction of the two. Correct inference? [haven’t done this before]. Most likely Yggy since no hum on any of the other 7 sources going into the 720, and Yggy’s the most recent change.
If I missed a step, please enlighten. Thanks much.
Ah… missed that so I’ll give you a little more info here.
CableTV is the source of this problem in many scenarios like this. The issue is that the cable line is grounded in multiple places including where it enters the home. They typically ground it to a water line or or the outside of the electrical panel, but never to the ground bus inside the panel. Because of this there is a significant difference in ground potential between the shield on the coax cable the the third prong of your electrical outlet. This causes a current to flow (at 60Hz frequency) between the cable ground (shield) and the closest thing that is connected to the ground bus in your electrical panel. The TiVo is ungrounded and the receiver is ungrounded so the next thing in line is the DAC. There’s actually a current flowing between the DAC’s ground and the cable’s ground and it’s riding on top of that single-ended interconnect! That’s where the hum is coming from. Unplugging the DAC from the wall eliminates that path and the current stops.
So… if you disconnect the cable from the TiVo (or the TiVo from the Anthem) and the hum stops then you need to break one side of that ground. I don’t suggest lifting the ground on the DAC as that’s a safety issue, but you can lift the ground on the cable line. Just pickup one of these: