Occasional hum

[CageyH]

If it is the heating, I have to live with it.

[struth]

i guess so.. still might be worth a trial, say with different things off etc.

[CageyH]

I am listening to the system (with no music playing) as I work, and there is much less hum now than there was last night.
During the day, I will turn lights on etc. And see if I can find the culprit.

[Macca]

is this a constant noise then? I thought it was intermittent?

[CageyH]

Nope. It comes and goes. Lasts around 2 seconds.

[Jimbo]

Sounds like something switching on and off on the ring main?

[CageyH]

If only I had a ring main...

The heat pump is a full inverter, so it could be this, as they are noisy.
Is there a filter that stops noise from Fridges/Freezers going back into the mains?

Will ferrites be of any help?

[Barry]

You could try ferrite rings/tubes on the SMPS; although most have one fitted already.

Regarding ring mains: they are no help in suppressing switching spikes - in fact in this respect the spur system is better, as the increased resistance of the path between the source of the spike and the recipient is longer (it has to go back to the meter and then back out again to your audio gear), and hence helps to suppress the spike.

[CageyH]

New discovery tonight - It is only on the analogue side of my system, so not likely to be a mains issue?
Makes me wonder if it is RFI or EMI now.

The digital side uses USB/coax into an Audio GD DI2014, which feeds the DAC via another coax cable. Connections between the DAC, Preamp and amplifier are all balanced.

On the analogue side, I use coax interconnects cables from SL1200 into the BB3, core for signal and shield as return, and a “balanced” RCA cable with the screen connected at the source end only, going from BB3 to Pre.

I think my money is on the last cable being the problem child.

[CageyH]

Having listened to a few sound effects on YouTube, it sounds a bit like a short 5G signal.