Ground noise with coax SPdif, current draw P2?

I know now what digital ground sounds like: white noise and beepbeep… unfortunately too loud, I hear it clearly at the listening position. This noise came in when I switched from usb to coax, now through the P2 reclocker. I found out that this is caused by a ground loop because my dac (Chord 2Qute) does not galvanically separate the ground at the SPdif input. I disconnected the earth wire at the mains cable at one power amp and the other amp has symmetrical XLR input. The noise is gone now but I want to be safe and connect the earth of one power amp again soon.
So I bought an iIfi iDefender. It disconnects the usb ground and 5V from my s30 to the P2.
I will use a good (but never aa good as my s60) spare audio grade power supply to feed the P2. The output voltage is turned down to 5V. Before I connect it, I would like to know the current draw from the P2. The supply has a very good transformer but it is 22V. That is a bit of a mismatch to the 5V output. This means that the supply will burn about 20V x the current flow.
I guess the P2 will not draw more than 0,5A since that is a sort of standard for usb, so power loss will not be more than 10 W. I also found that a particular femto clock by itself doesn ‘t need more than 3,3V and 0,02A. If that is the case then I can safely use my power supply, it may burn about 24Watts. Before it really burns :thinking: . Like a class A amp :grinning:.
Does anyone know the current draw of the usb-reclocker P2?

By the way: my dac sounds way better with the P2, it is not a subtal change in sound quality.

What’s a P2?
I presume not an Antipodes product?

Yes it is, it is the old Antipodes reclocker that would fit under the ex. I like it a lot because it also acts as an isolation base for my Chord dac.

Before my time I’m afraid

All Antipodes devices adhere to the USB2.0 standard.
This is 5v / 500mA

Thanks! That should work.

I would be interested to know if the iDefender solves the problem. I had the iFi GND Defender (a C13 type ground loop plug) on my power amp until yesterday, when I started trying out a different preamp and then found I no longer needed it installed. I tried it on almost every box (including S60) before finding that it only solved the ground loop when on the power amp. I didn’t know about the iDefender.

Yes it did solve the problem.
Does your new pre-amp have a different/ no ground/earth connection? Most analog sources dont’t have a ground connected to mains earth but “computers” and a lot of (non-Japanese) amps do, so there you have a ground loop through the rca-ground connection and mains earth from amp and computer. Symmetrical XLR connections could also solve the problem, because they usually don’t connect the signal’s ground.

I first connected the normal powercord back to the amp to hear the ground noise again. Then connected the iDefender and powersupply (the iDefender comes with an adapterplug for the 5V connection) and the digital noise was gone. And the powersupply does not get too hot. :grinning:
The iDefender’s plug has a better grip than the connector of the Wireworld usb cable. The sound is a bit more detailed and smoother without loosing clearity. I don’t know if that is due to the digital and analog ground being separated or this combined with the Puritan powercord back on the amp and the removal of the Audioquest jitterbug that sat there between s30 and usb cable where now the iDefender is.
But it sure sounds very nice to me. It is not a secret that Chord dacs sound better with SPdif than usb and they can still play dsd ( you can see in the picture the light in the dac that turns blue with dsd).

@arjan As you say it is a well known thing that Chord DACs sound best when using the BNC input rather than USB (or optical).

If your amps use XLR in a properly configured balance signal way then the XLR signal does not require the earth to be connected. Often therefore I connect the XLR screen to earth at one end only (usually source end) and that way there is not ground loop connected.

@arjan Good to hear that you solved your loop with the iDefender.

My new and old preamp boxes all had earth pins, which I assume were in-use.

The previous Naim preamp had two power supplies, one of which actually sits between the pre and the power amps with the wiring (they are known for doing things different with cables). The 3 boxes needed 2 power cords total. I’m guessing that may all lead to extra potential locations for a ground loop in my system.

arjan and @NickBacon The new (to me) preamp is a single box ARC Ref 3, which uses balanced XLR cables to the DAC. These are the first balanced cables in my system, so perhaps this could be what solved the loop.

Whichever it was, I’m glad to have it sorted. The GND Defender was a godsend when I needed it, but not needing it should be even better.

@Artoly: the balanced connection probably solved the problem, as the +signal is not “measured” against the ground, but against the -signal. The pin “1” in an XLR is usually (as NickBacon also said) connected to the cable shield and chassis and earth but not to audio-ground in the balanced circuit. My power amp for the subs has a balanced input and I made a special cable from rca to XLR. I read that a Naim preamp connects the grounds to the ground of the Naim cd-player, which is the only Naim device that is connected to mains earth.
@ NickBacon: I think Chord is optimised for bnc because their M-scaler is also connected with bnc/coax. The first pleasant surprise I had with the Chord was when I connected a better power supply. The second time was when I connected the P2 reclocker to it.

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@arjan Just on the Chord thing with bnc inputs, many of the current devices predate the release of the Mscaler (such as the Dave) so in reality it is just that the implementation of the BNC inputs is better than the other inputs rather than that the BNC inputs were designed around the Mscaler.

Power supplies matter. I have reconfigured my Dave to use two external linear power supplies (one for the digital circuits and one for the analogue circuits) that cost as much as the Dave and are about 8 times bigger than the Dave. But boy does it sound good.

You are absolutely right. In the analog world we are in fact listening to our power supplies modulated by the signal. I like what Antipodes is designing. It brings us closer to perfection.
I feed my little 2Qute with a current source. Not very efficient but it sounds muscular, quiet and controlled. Never understood why Chord says that upgrading the cheap wall supply doesn’t help.