audio interference from ethernet

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fitpchenk
Posts: 6
Joined: Wed May 02, 2012 8:09 am

audio interference from ethernet

Post by fitpchenk »

I just bought a Fit-pc2 to stream audio to my amplifier and am getting a lot of interference from the ethernet port. The setup is:

- diskless fit-pc2 with filesystem mounted via NFS
- gigabit ethernet connection (but forcing the port to 100Mbit doesn't make any difference)
- line-out to RCA plugs on the amplifier
- MPD streaming audio to line-out

I initially had this hooked up to a pair of PC speakers as a test and that worked fine. But with the box hooked up to the amp any activity on the ethernet link causes so much interference (sounds like an old analog modem) that it is essentially impossible to listen to music.

I like this box a lot, and was thinking of putting a couple in the rest of the house, but this makes it unusable unfortunately. I will look at using the SPDIF with a DAC, but that's an extra expense that I'd like to avoid.

Has anyone else run into this problem?

Henk

gabrielh
Site Admin
Posts: 1260
Joined: Thu Jun 02, 2011 1:13 pm

Re: audio interference from ethernet

Post by gabrielh »

Thank you for submitting this bug. Unfortunately we are not familiar with this issue. The best setup for the FitPC2 with an amplifier, is to connect the SPDIF out to the amplifier's coax input.
Gabriel Heifets

Fit-PC2/3/IntensePC support.

fitpchenk
Posts: 6
Joined: Wed May 02, 2012 8:09 am

Re: audio interference from ethernet

Post by fitpchenk »

Well it seems it would be easy enough to test :) Connect the line-out to an amplifier (I'm testing with a Quad 405, 500mV sensitivity, 20k||220pF impedance) and listen to the speakers. Unless I have a buggy unit you'll hear the ethernet traffic.

As I said I'll test with the SPDIF output, but that's an extra expense (and clutter) that I had not counted on.

Is the SPDIF output coax or optical?

Henk

gabrielh
Site Admin
Posts: 1260
Joined: Thu Jun 02, 2011 1:13 pm

Re: audio interference from ethernet

Post by gabrielh »

the SPDIF is coaxial. Do you have a coaxial input on your amplifier(receiver? )?
Gabriel Heifets

Fit-PC2/3/IntensePC support.

fitpchenk
Posts: 6
Joined: Wed May 02, 2012 8:09 am

Re: audio interference from ethernet

Post by fitpchenk »

No, which is why I will have to buy a DAC (Digital-Analog Converter) and as I said that's an extra cost that I had not counted on.

Henk

fitpchenk
Posts: 6
Joined: Wed May 02, 2012 8:09 am

Re: audio interference from ethernet

Post by fitpchenk »

Ok, I've spent quite a bit of time over the past weeks trying to get this to work but I still get interference. My setup is:

file server (audio file + NFS) -- fitpc2 (diskless, filesystem on NFS) -- Cambridge Audio DAC -- Quad 405 amp -- Rogers studio monitors

The DAC (digital analog converter), amp and speakers are all high-end audio kit. The fitpc2 -- DAC link is SPDIF coax using the cable supplied with the fitpc2.

I've checked earth, routed cables a bunch of ways, tried various ways of shielding. Makes no difference: I can hear the ethernet clearly (and loudly) whenever there is traffic. And because the music is streamed off the file server, that means whenever I play music. The box is essentially useless to me.

Is it possible I have a broken unit? How do I get this fixed?

gabrielh
Site Admin
Posts: 1260
Joined: Thu Jun 02, 2011 1:13 pm

Re: audio interference from ethernet

Post by gabrielh »

Please try to mute all internal codec inputs
Gabriel Heifets

Fit-PC2/3/IntensePC support.

fitpchenk
Posts: 6
Joined: Wed May 02, 2012 8:09 am

Re: audio interference from ethernet

Post by fitpchenk »

Gabriel,

Thanks for the effort but this is going nowhere. I've built a number of high-end multi-media PCs, I have a lot of experience in high-end audio, I know what I am doing. Of course I have muted all inputs (and outputs) that are not in use (all except for spdif). I've also, by now, spent a huge amount of time trying to get this to work. Your system is broken, either just my specific box, or there is a general design problem. How can I get this fixed? I like the idea of the Fit, so if you want to swap the box I am willing to spend a little more time on this, otherwise I want to return it. Right now it's a $300 paperweight.

Henk

P.S. It doesn't help to have to wait 9 days to get such a trivial answer to my post.

gabrielh
Site Admin
Posts: 1260
Joined: Thu Jun 02, 2011 1:13 pm

Re: audio interference from ethernet

Post by gabrielh »

I am sorry for a delay. We were tried to go in a different ways to reproduce this problem, and right now, we are unable to see it with our current equipment
Gabriel Heifets

Fit-PC2/3/IntensePC support.

fitpchenk
Posts: 6
Joined: Wed May 02, 2012 8:09 am

Re: audio interference from ethernet

Post by fitpchenk »

OK, so what's the next step?

Note: I get exactly the same symptoms (I hear the ethernet traffic) at the same volume whether I use the SPDIF signal or the analog line out. I've tried the following setups:

- analog line-out -> amplifier

- spdif out -> cheap DAC -> amplifier

- spdif out -> expensive DAC -> amplifier

The same symptom in all cases. To me this says that the interference is being injected into the audio path at a point common to analog and spdif. Which seems to me can only be ground.

Note 2: the Quad is a 100W amp, you may not hear the noise if you are testing with a lower power amplifier.

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