This reads a bit like you have massive leakage current generated by your computer, flowing over your headphones and your body to earth. So let's clear this first: does the noise on the headphone go away when your body is fully isolated from ground? Test can be as simple as sitting on an office chair with plastic wheels and lifting the feet up, away from ground.

If all the noise is just internal electronic noise, not related to ground, then either your computer has no ground/PE or your power outlet does not have, it seems.

What excatly do you mean with 'new output mute feature'? The AIO Pro uses relais on both line and headphone output for click-free on/off when turning on the computer and turning it off. A little click might still get audible, but no loud pop/thump should occur. Or are you having this effect when waking from sleep? You use the latest firmware 23 / 108?

Some questions,
Did you ever try different headphones and if yes was the noise identical?
If you set the level of the headphones low or off in the AIO control app, not totalmix, does the noise change?

Hi again, Matthias.

I tried the above, nothing changed in the interference on the headphones out. Could it be the breakout cable is damaged in some way? I can't afford to grab a new one yet.

The Outputs with Mute Relais feature might actually be working then. I defo hear a click but it isn't anything major.

I have emailed my computer build company to see if they have any ideas. I am not clued up on the electrics side of things, so I personally wouldn't know without major problems showing if my PSU is faulty, failing or grounded.

The surge protected extension leads I own seem to show up the 'earthed light' on my sockets.

Cheers!

I just tried another two sockets in the room with just my computer,  AIO Pro, headphones and monitor connected, no luck. Like I say, even does it with nothing conncet to the machine other than the card, balanced breakout and headphones.

I did re try all settings in the BIOS again, tired these a lot. The only thing that does seem to cut out the high pitched whine is disabling all C-States like I said, but then there's still the constant sizzle, crackling, all mouse movment, apps open ect getting picked up.

I will try taking just my computer down stairs into another room and trying a socket, not holding much hope though!

I can live without the headphones out, but for 9 years it's always played on my brain as to why it's doing it here!

Thanks.

You could try isolating the AIO bracket from the computer case. Remove the screw that fixes it to the case and use some thin plastic to isolate it from the case. I give it only a 20% chance but it is easy and without risk.  If it helps it would mean the PSU noise is reaching the headphones through the case to the sleeve of the headphones plug.
Cheers!

Tried a few more things, no luck again this time round.

I have just linked all my gear back up. I am really liking the new converters on the Pro! Sound great to me out of my old faithful Adam P11a's and SPL Volume 2. Card is syncing well in my setup, ProTools running fine at 96khz. I'll just try to forget about the Headphones out issue. I have a few other options for headphones!

No point chancing messing up a solid  recording and mixing system!

Cheers to Matthias and Vinark for their input.

Just a quick update. The DAW company who built my machine/s got back to say,

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'the PCs are grounded and in all builds we use the same brands of PSU. I've never come across an issue like yours where the problem only arises with an RME card installed.'

'If it's coming through the headphones via the RME card, then there must be something between the two devices that is causing it, but what that is I can't say'

'Only known grounding issues in the past was usually on the users end with studio monitors through a USB interface, and not headphones, and is easily remedied with a ground loop isolator'

'I did recently install a Raydat card in a customers machine he has had no issues (using very simillar components)'
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I have used the company for years on my builds, always great and really helpful. I get that the Raydat is pure digital, no analog, so a different setup to the AIO's.

Like I say, I maze well carrying on and forget about the headphones out as it's nothing ultra major. Just an annoying thing thats stored in my mind I can't seem to solve over the years!

Cheers.

I don't have any other lower impedance headphones at hand, other than the iPhone freebies.

Unfortunately, I don't have a hifi at hand.

Any ideas on the higher impedance headphones front and intereference?

9 years I've had problem with AIO's, then plugin in a cheap pair of headphones, noise gone.

I found an old pair of Nokia in ear headphones. Plugged them into the breakout, no interference again.

Trouble is, all these phone type headphones have 3 rings, which I think one is for their built in mic, TRRS?. The headphone adapters I have been trying are standard 1/4" trs type, 2 rings.

Cheers for getting back again.

Yeah, I tried a standard trs 1/4" adapter.  The thing is all the cheap free iPhone (standard white type), Nokia phone type headphones I have are 3 ring mini, trrs type.

When I conncet a normal trs 1/4" adapter, the signal is out of phase and mono, so that might be why the interference goes. The wires are out of phase testing this way.

Shame, I fault the interference went with lower impedance headphones, looks like not to be the case.

I have a bunch of trs 1/4" adapters. I will try a few.