Issue with SPDIF Input Circuit by Elso and Jocko - diyAudio
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Old 6th April 2005, 09:46 PM   #1
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Default Issue with SPDIF Input Circuit by Elso and Jocko

Elso, Jocko at al,

My problem is that the spdif input circuit works beautifully with my Philips 963sa DVD Player and my Emu 1212M computer soundcard, but fails to work properly with my Musical Fidelity A3 CD player. I say "fails to work properly" because it *does* work, except the SPDIF cable has to be loose in that only the signal part of the connector is left connected and the ground part is left disconnected. Does anyone know why this is happening? The Musical Fidelity worked before with the stock CS8414 input cap set up. The cd player also works with my Denon Receiver, so I know the musical fidelity is working properly.

Thanks,
300_baud

Edit: This is the schematic i'm using: http://www.diyaudio.com/forums/attac...amp=1026982395
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Old 7th April 2005, 03:15 AM   #2
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How did I get dragged into this? Elso is the King of Comparators. I hate 'em. All I did was tell him how to set up the impedance properly. Give me some time to recover from my road trip before I look at it in depth.

Jocko
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Old 7th April 2005, 07:26 AM   #3
tubenut is offline tubenut  South Africa
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Musical Fiddle Tea as some technician friends call it often has odd ideas that may sound good in some applications but are not always universally compatible.....

One friend called their Odysseus amplifier the Audacius.... He found this beast to have too much feedback applied sending the amplifier into oscillations....

Anyway, just a guess but have you checked for DC on the MF digital out....

The denon used to "test" and isolate the problem is probably designed safe with either a transformer or cap blocking DC.....

G
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Old 7th April 2005, 12:47 PM   #4
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Jocko: I just read in the thread that you were somewhat involved with the schematic. Don't take it the wrong way if I misunderstood you

Tubenut: I've measured the DC offset from the Musical Fidelity A3, and it reads 0.448 volts. As per the spdif input schematic, I have input caps in between the AD8561 comparator and the CS8414. Should I have an input cap before the AD8561 instead?

Thanks
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Old 7th April 2005, 01:58 PM   #5
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Guys i figured out the problem,

Tubenut provided the correct clue, which was the DC offset from the musical fidelity. Putting an input cap before the AD8561 solved the problem.

Take care,
300_baud
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Old 7th April 2005, 02:50 PM   #6
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I should also add that i removed the caps that were in between the comparator and the cs8414. It sounds a lot better when there is a cap before the comparator than afterwards.
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Old 7th April 2005, 02:52 PM   #7
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SPDIF should be DC-free by definition......Of course DC affects the tripping level of the comparator. Have a 100k resistor to ground after the cap for the leakage current in/out the comparator.

Jocko, glad I am King of something! (and not King Gang Bang!!)
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Old 7th April 2005, 02:54 PM   #8
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Quote:
Originally posted by 300_baud
I should also add that i removed the caps that were in between the comparator and the cs8414. It sounds a lot better when there is a cap before the comparator than afterwards.

I know, I know.
Jocko knew it all along.......
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Old 7th April 2005, 02:54 PM   #9
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Quote:
Originally posted by Elso Kwak

Jocko, glad I am King of something! (and not King Gang Bang!!)
Who knows what the future may have in stall !
__________________
No More Mr Nice Guy
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Old 7th April 2005, 02:57 PM   #10
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Default Re: Issue with SPDIF Input Circuit by Elso and Jocko

Quote:
Originally posted by 300_baud
Elso, Jocko at al,

My problem is that the spdif input circuit works beautifully with my Philips 963sa DVD Player and my Emu 1212M computer soundcard, but fails to work properly with my Musical Fidelity A3 CD player. I say "fails to work properly" because it *does* work, except the SPDIF cable has to be loose in that only the signal part of the connector is left connected and the ground part is left disconnected. Does anyone know why this is happening? The Musical Fidelity worked before with the stock CS8414 input cap set up. The cd player also works with my Denon Receiver, so I know the musical fidelity is working properly.

Thanks,
300_baud

Edit: This is the schematic i'm using: http://www.diyaudio.com/forums/attac...amp=1026982395

You should use the improved schematic.
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