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Old 22nd July 2003, 11:18 PM   #1
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Default SPDIF Transformers

Old PC network cards are free for the asking nowadays.
Are the transformers suitable for Spdif input/output ?.

Eric.
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Old 23rd July 2003, 12:34 PM   #2
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Fred ?.
Jocko ?.

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Old 23rd July 2003, 04:37 PM   #3
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are these 1:1 pulse transformers such as Digikey part # 257-1015-nd?

This one is actually OK'd by Crystal for CS8414/8412.
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Old 23rd July 2003, 05:46 PM   #4
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Default Transformers

No(MF) and No(H)

I looked at the specs for dozens of thse and they were really not very suitable. The best sounding commerical ones are in the Monarchy DIP. This was a few years ago and they may have changed types for all I know.

With a few mods the DIP was the best sounding device of its type and blew the DTI Pro and Ultra Jitterbug digital interface devices away. Even stock it was better than either of those two. I have not heard the new one though.


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Old 23rd July 2003, 06:37 PM   #5
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Minicircuits and Scientific Conversion make nice transformers for SPDIF. I can recommend Minicircuits T4-6T.

http://www.scientificonversion.com/mission.html

http://www.minicircuits.com/transf.html
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Old 23rd July 2003, 07:11 PM   #6
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Thanks Fred but

I didn't say that pulse transformer was "good sounding". I just said it was spec'd by Cirrus as a recommended transformer:

http://www.cirrus.com/en/pubs/appNote/AN134-4.pdf


I might give one of the above mentioned transformers (F, JP) a try myself..
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Old 23rd July 2003, 10:49 PM   #7
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Thanks all,

Eric.
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Old 23rd July 2003, 11:08 PM   #8
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Default Been there, done that

" I just said it was spec'd by Cirrus as a recommended transformer"

Yes an I have talked with John Marshall at Schott who designed it. I have done enough measurements to tell you the shortcomings of these and sevral of the designs from Scientific Conversion. There are real measured and sonic differences is pulse transformers. I spent a year refining my design and have measured and listened to over a dozen other designs.
Most pulse transformers are designed for the absolute minimum capacitance between windings to the detrement of every other parameter. SPDIF transformer design is an art and one of the most difficult designs I have ever done.
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Old 24th July 2003, 04:16 AM   #9
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This is usually the part where I get booed off the stage, but in a digital system you need to get the bits from one end to the other without errors and with a specified average rate. If your architecture relies on decreasing the standard deviation of edge-to-edge arrival times, your architecture is broken.

The scientific conversion and schott transformers are good enough because they get the bits into the receiver without degrading the signal. Anything else is overkill. If you can get the interface up and running without any pulse transformer, that is even better.

Synchronize the clocks in the transport and the DAC, buffer the signal in the DAC to reject jitter, and make sure your word clock (bit clock for ΣΔ designs) is low-jitter. Case closed.

-jwb
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Old 24th July 2003, 06:09 PM   #10
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Quote:
Most pulse transformers are designed for the absolute minimum capacitance between windings to the detrement of every other parameter. SPDIF transformer design is an art and one of the most difficult designs I have ever done.
Fred, which are the important parameters ?.
What sort of sonic differences do you find ?.
I could not find an Audient page - have they evaporated ?.

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