Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Spike1000]

Greetings all,

Just trying to get my head around a MC/Network (audio) Streaming setup for my house. Wow, there's a lot of permutations!  ?

At the moment I'm not sure if I'll play audio straight from the server or via a renderer over DLNA.

If I use a desktop PC for the server (this will be earthed at the mains as I'm in the UK) and then a USB DAC to my earthed audio amplifier (it's not double insulated) won't the earth from the PC and the amp be connected via the screens/earth of the USB into the DAC and the screen of the analogue out? This would give me a loop and therefore a mains hum?

If I used an optical link from the PC the DAC there be no earth connection so no loop. . . . but as mentioned on this forum many times USB DACs seem to be the way to go these days they are more flexible than toslink optical connections.

Any advice gratefully received.

Cheers

Spike

[mwillems]

The best (meaning surest) advice is to use balanced connections between your DAC and your AMP (assuming both DAC and AMP support them).  Balanced connections are entirely insensitive to ground loops and will eliminate the problem. 

If you have to use unbalanced connections there are some wiring/cabling tricks you can do to minimize hum (especially if one or the other side has a balanced connection), but ultimately you're at the mercy of your equipment at that point. 

If you're buying new equipment, look for equipment with balanced connections you'll be glad you did (and not just because of ground hum, they also reject line noise and all other sorts of common mode interference)

I'm in the U.S. so my situation is a little different, but I have connected several different USB DAC models (about a dozen) to various amps and most of them produced no hum.  Some of them did/do.  It's ultimately a question of the way the rooms and equipment in question are wired, and I know of no good way to predict whether you will or won't get a hum other than using a) optical or b) balanced connections between DAC and amp.

[Spike1000]

Many thanks mwillems for you speedy and informative answer!

Have bought a Audio-gd DAC as a project (I've only got the PCB and the volume pot!) so that needs more time to finish than I was expecting  In the meantime I'm looking into 'network' DACs (network players) like the Arcam AirDAC or the  Raumfeld Connector 2 as I need one of those for another room in my house.

Cheers

Spike

[Spike1000]

Just to follow up my own post. . .

Have tried an Audio-gd mains powered DAC (one that's actually complete and not still in 'kit form' like my other one) and no mains hum or mains loop. Result!

I think I understand why. . .
The mains earth in the DAC is connected to two diodes, in parallel, but in one forward and one reversed (they are both in parallel with a low value resistor (10R I think)). This prevents any current flow to earth until the mains earth potential exceeds +/- ~0.7V thus effectively preventing a loop under normal (non-failure) conditions. It certainly works, but I'm not sure if it would pass a PAT test here in the UK. . .    

Cheers

Spike