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Old 27th February 2007, 12:47 AM   #1
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Default DAC cutting out

Hello,

I saw someone else mention this problem in a different post, but was unable to locate a thread.

My DAC (CAL Sigma/chaintech AV-710) loses sync, everytime a large load kicks on in my house.

I have switched plugs around, in and out of back-up supply, different circuits.

Switched PCI slots/drivers for sound card.

I am unable to determine if it is the PC or the DAC, as switching the soundcard off kills the signal.

Any ideas would be appreciated.

Eric
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Old 27th February 2007, 01:59 AM   #2
Foxx510 is offline Foxx510  Australia
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I guess the first step is to find out where the switching impulse noise is entering the dac signal. It will either be coming in via the 110v, or radiated RF which I think is more likely. My refridgerator kicking in causes my digital tv signal to drop out for a second. Try listening on a transistor radio when the switching occurs and see if you can hear it. If it is radiated RF noise you will have to look at better shielding, including any cables. If you have a SPDIF coaxial connection, try some high quality quad shield cable.
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Old 27th February 2007, 02:27 AM   #3
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When PCI audio cards act up ... first thing = replace the computer power supply with something at least twice as large as that el-cheapo unit that came with your clone ...

In your case, this solution is top priority as you are reporting an external power line related condition.

To test this, remove all internal plug in cards except those absolutely necessary to make your computer boot and run ... then plug the audio DAC back in ...

Second option is to get an external DAC ...
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Old 27th February 2007, 02:41 AM   #4
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Default Thanks for the input.

For the record, the Cal Sigma is an external DAC. I believe (for some reason, it has a more than adequate power supply).

I think it is really my soundcard, but I would like to figure out if I need a different soundcard or the problem is external to it and would migrate to the new soundcard.

I am using toslink which AFAIK is immune to RF interference, so it has to be the DAC or soundcard itself.

Any ideas on RF shielding would be helpful, as I think that would be my only option...beyond power conditioning, which isn't in my budget right now.

Eric
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Old 27th February 2007, 04:02 AM   #5
Foxx510 is offline Foxx510  Australia
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Ok I guess the next step is to find out where the interuption is occuring, so do you have another toslink source you can try to find out which unit is causing the problem?
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Old 27th February 2007, 04:26 AM   #6
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Default unfortuately...no

That would certainly simplify things.

I guess I was wondering if there is any quick and dirty way to try shielding things to see if it helps.

I assume the DAC is sheilded and the PC is in a Steel PC case. So where does the RF get in? Power cords?

Wouldn't the interference be filtered out by the power supply if it got in before? So wouldn't that eliminate anything except shielding the sound card itself?

I know it's impossible to figure out remotely...just looking for suggestions.

Thanks for the effort.

Eric
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Old 27th February 2007, 04:37 AM   #7
Foxx510 is offline Foxx510  Australia
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I would be suprised if the noise was getting into the soundcard, but I could be wrong. I have always thought that pc powersupplys made pretty clean power. It could be getting into the dac powersupply I guess via the mains. Could you borrow a dvd player from a mate or neighbour to test the toslink and narrow it down? Another thing to check is the actual contactor on the heating unit that is making the noise in the first place. You might find it has dirty contacts and is arcing more than it should be. An electrician will probably be needed for this though. It is hard to shield things well in a temporary mannor, but I guess putting the dac in a large metal box that is earthed would be a start.
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Old 27th February 2007, 05:02 AM   #8
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Default hmmmm

Thanks for that advice.

I had to replace a main power relay thingy (part relay, part breaker) on my actual heatpump, a few months ago, due to it malfunctioning.

I bet the airhandler has a similer power relay. I will find it and examine it tomorrow.

Thanks.

Eric
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Old 27th February 2007, 05:09 AM   #9
Foxx510 is offline Foxx510  Australia
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No worries. Do let us know how you go with sorting it out.
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Old 2nd March 2007, 04:33 AM   #10
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Default close enough, I guess.

Thanks again, for the ideas.

I cleaned the relay contacts (Too cheap to replace the relay itself). That got the most improvement. It freaked out, only a couple of times yesterday.

But, switching PCI slots helped a bit more today and it seems not to be at all related to PC usage, but always triggered by an outside event. So I might try a bigger PSU on my computer too. It is still annoying, but only happens occasionally now. Before I couldn't listen to a whole song, on a cold windy day.

Of course, I don't care too much about this PC, as I plan to make a new one as a music server. I just wanted to work the bugs out of the software and audio hardware, before I put it all in it's own box.

Thanks again

Eric
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