Hi-fi electronics question

doctor-bond · 2024-12-23T18:50:53+0000

I know there are some knowledgeable hi-fi and electronics people on here, so to save joining another forum, I’ll post this here.

I’ve just hooked up an Arcam irDAC (lovely Burr Brown PCM1796 chip) to my faithful Arcam Delta 170 transport. The sound is impressive, but the transformer that comes with the irDAC is causing a little noise (background hum). My power amp is a Creek with a toroidal transformer.

Is the dac’s transformer infecting the mains (DC offset?) and causing the hum? I have it plugged into a separate mains socket to the amps, but it’s still there.

Are all DC power supplies for modern DACs like this or is it down to this particular power supply?

thanks!

legrandefromage · 2024-12-23T19:17:56+0000

Is the hum only from the one source or all the amps inputs?

Looking at pictures, it looks like the dac has a generic little switchmode power supply.

If it's 12v dc, any good quality psu should be OK, as long as the polarity on the plug matches of course

Router psu are usually pretty good. My old sky box uses a 2amp 12v which has been great with other electronic gear

KermitGKona88 · 2024-12-23T19:19:45+0000

I was literally tagging you and bam you were here...

legrandefromage · 2024-12-23T19:28:15+0000

sometimes the old transformers can breakdown as the coating fails

Capacitors too, age gets to them

Takingabreak · 2024-12-23T19:50:39+0000

I feel like I should be throwing on some vinyl

Like batman

doctor-bond · 2024-12-23T21:59:31+0000

Thanks LGF: the hum is across the board, which makes me think it’s getting into the mains and upsetting the power amp. The power supply is not original spec and is a beefier upgrade: constant reliable 12v (according to previous owner) and 5A.

I will experiment with some different PSUs. Am I right in thinking that the 1.5A printed on the back of the DAC is just what it needs to draw, and a higher (amps) rated PSU will provide that on demand with some headroom?

(For the record, the irDAC and Delta transport still can’t top my Systemdek IIX/ Rega RB250, even with a modest AT95 cartridge

)

legrandefromage · 2024-12-24T15:42:39+0000

Try a different amplifier, if the hum is still there it's likely a ground fault on your mains.

Best thing anyone can do is get a dedicated ring mains for your hifi and video equipment set up by an electrician.

You won't need conditioners or fancy filtering then

legrandefromage · 2024-12-24T16:34:41+0000

...and 5 amp may be too much!