Technical help please! Optical Digital to Audio converter only working on one channel. - AVS Forum
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post #1 of 8 Old 01-11-2013, 10:04 AM - Thread Starter
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Hi All - would really appreciate some help troubleshooting this:

Have purchased two different (but applications-similar) DACs to get the optical digital out from my Vizio flatscreen (PCS formatted) into my Onkyo receiver (RCA) and speakers.

The problem I am having is that only the left RCA channel output of BOTH converters carries signal and the right channel is dead.

I have thoroughly troubleshot the receiver and the RCA cabling - they are not my issue. I thought the first DAC was faulty so replaced with a radio shack model and got exactly the same result.

As there is clear sound passing through the left channel, I don't think this is an optical cable issue. And though I am certain it *could* be a possibility, what are really the chances of this being two bad converters (with exactly the same 'problem'), from two separate manufacturers?

Sooo what am I missing and what would you tech-capable folks recommend I do to further troubleshoot the DAC, optical cable or TV end of things?

Very, very appreciated - I am frustrated,
Matt
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post #2 of 8 Old 01-11-2013, 10:23 AM
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If you swap the left and right RCA plugs does the sound move to the other speaker? If so this indicates a problem with the converter or the source (tv). If not, then the problem is somewhere in your receiver.

I can tell you one thing it's not and that is a bad optical cable. The left and right are multiplexed together at that point so you get both or none as far as the cable is concerned. But hey, if you have an extra cable try it anyway. Just don't run out and but some expensive optical cable because that's not going to fix it.

Do you have a CD or DVD player with optical out. If so, try connecting the converter to this and see how it works.

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post #3 of 8 Old 01-11-2013, 10:27 AM
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Quote:
Originally Posted by Makakio View Post

Hi All - would really appreciate some help troubleshooting this:

Have purchased two different (but applications-similar) DACs to get the optical digital out from my Vizio flatscreen (PCS formatted) into my Onkyo receiver (RCA) and speakers.

The problem I am having is that only the left RCA channel output of BOTH converters carries signal and the right channel is dead.

I'd point the finger at either the cables between the DAC and the receiver, or the receiver itself.

Does the receiver have an optical digital input? If it doesn't it must be a zillion years old!

If the receiver has a digital optical input, how does it work?
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post #4 of 8 Old 01-11-2013, 11:27 AM - Thread Starter
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Quote:
Originally Posted by Glimmie View Post

If you swap the left and right RCA plugs does the sound move to the other speaker? If so this indicates a problem with the converter or the source (tv). If not, then the problem is somewhere in your receiver.

I can tell you one thing it's not and that is a bad optical cable. The left and right are multiplexed together at that point so you get both or none as far as the cable is concerned. But hey, if you have an extra cable try it anyway. Just don't run out and but some expensive optical cable because that's not going to fix it.

Do you have a CD or DVD player with optical out. If so, try connecting the converter to this and see how it works.

Thanks Glimme - I have tried swapping and it does indeed come out of the other speaker, hence you are correct and it is NOT my RCA cables nor my receiver.

Thanks also for the tech deets on the optical cable - nice to eliminate that as a possible source. So it's almost certainly the DAC or TV.

Could two DACs from different mfgrs really be bad?! What are the odds?!

Looking at the Vizio TV, I have the output set to PCM, so what else might I check there. Could it be as simple as speaker balance?!?!
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post #5 of 8 Old 01-11-2013, 11:33 AM - Thread Starter
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Originally Posted by arnyk View Post

I'd point the finger at either the cables between the DAC and the receiver, or the receiver itself.

Does the receiver have an optical digital input? If it doesn't it must be a zillion years old!

If the receiver has a digital optical input, how does it work?

Hi Arnyk - thanks for the feedback. I think we've eliminated the receiver and the RCA cabling as the problem by simply testing both cable and receiver LR channels on the working (left) channel of the DAC. I have also tested this on various inputs at the receiver, all with the same result. If the receiver had an optical digital input I wouldn't be messing with the DAC -- it is indeed a zillion years old in audiophile years (or about 10 actual years in fact - a brilliant Onkyo connected to Polk studio speakers that develop great sound (to my low-fi ears at least). wink.gif
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post #6 of 8 Old 01-11-2013, 11:51 AM
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Quote:
Originally Posted by Makakio View Post

Quote:
Originally Posted by Glimmie View Post

If you swap the left and right RCA plugs does the sound move to the other speaker? If so this indicates a problem with the converter or the source (tv). If not, then the problem is somewhere in your receiver.

I can tell you one thing it's not and that is a bad optical cable. The left and right are multiplexed together at that point so you get both or none as far as the cable is concerned. But hey, if you have an extra cable try it anyway. Just don't run out and but some expensive optical cable because that's not going to fix it.

Do you have a CD or DVD player with optical out. If so, try connecting the converter to this and see how it works.

Thanks Glimme - I have tried swapping and it does indeed come out of the other speaker, hence you are correct and it is NOT my RCA cables nor my receiver.

Thanks also for the tech deets on the optical cable - nice to eliminate that as a possible source. So it's almost certainly the DAC or TV.

Could two DACs from different mfgrs really be bad?! What are the odds?!

Looking at the Vizio TV, I have the output set to PCM, so what else might I check there. Could it be as simple as speaker balance?!?!

The TV might still be on the hook. You need to test the DACs with some other optical digital source, or find another known good DAC.

Usually the TV's audio controls such as volume, balance and tone don't affect the DAC output. It is still worth reading the TV's manual to be sure those items are all OK.
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post #7 of 8 Old 01-11-2013, 03:00 PM - Thread Starter
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Thanks Arnyk - will go through t-shooting on the TV but was indeed wondering if the sound controls on the TV affect the optical signal output characteristics...
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post #8 of 8 Old 01-15-2013, 02:29 PM - Thread Starter
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Hi all - just thought I'd loop back around and close out this thread.

So after both DACs not working I simply went to Radio shack and got a 3.5 male-to-RCA connector and used the headphones out on the back of the TV (which can be configured to static output via TV menu) and got fine sound. Certainly not optical quality or HDMI, but for my purposes works just fine.

I appreciate your inputs - best to you all.

Matt
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