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Old 1st September 2014, 10:50 AM   #1
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Default SPDIF transformer and signal quality.

Hi.

SPDIF transformer breaks ground loop, but can it distort the digital signal? For example PE-65612NL which I want to buy.

The second option is use Toslink, but in this in this topic is a lot of different opinions and I do not know if it is worth.
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Old 1st September 2014, 10:56 AM   #2
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I've been using PE-65612NL for several years in my DAC designs without issues.
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Old 1st September 2014, 12:05 PM   #3
Eldam is offline Eldam  France
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I bought a murrata RF 1:1 for one of my two SB Duet and lazy to implement it to an AB test (with ears)...

Some designs do not use it with sucess as the Subbu DAC.

If one transformer : position have to be nearer to the end of the line (source) than the beginning (streamer, player) or not important ?
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Old 1st September 2014, 12:16 PM   #4
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Quote:
Originally Posted by Eldam View Post
Some designs do not use it with sucess as the Subbu DAC.
As it is not a must, just a good to have safety feature. 1 is enough where ever you like.
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Old 1st September 2014, 12:45 PM   #5
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I prefer to put the trafo at the receiving end, after the termination resistor. The grounding is important as the S/PDIF link is a means of introducing CM noise into a DAC.
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Old 1st September 2014, 01:21 PM   #6
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According to the datasheet the pe65612nl is only ok up to 96khz, but has anyone done tests? Murata is more expensive but doesn't have this (apparent) limitation. Lundahl also make a decent one too (more expensive again)...
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Old 1st September 2014, 04:54 PM   #7
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The easiest solution is to leave for example one input without transformer, because PE-65612NL is up to 7mbps and 192kHz/24bit needs 9.216 Mbps.

192,000 (samples per second) x 24 (bits per sample) x 2 (channels) = 9.216 Mbps.
S/PDIF max bitrate? - AVS Forum

Unless someone checked this transformer with 192kHz/24bit...
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Old 1st September 2014, 05:57 PM   #8
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Worth reading: The SB3/SPDIF output thread.......
PE-65612 measurement on page 2.

@elektryk
Yes, transformer can distort signal.
Leaking inductance, interwinding capacitance, line impedance, reflection coefficient (return loss) are keywords. And for 192k/24bit, you will need transformer with >100Mhz bandwidth.
In general, if you can't measure it, better leave it out of circuit, it will do less harm.
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Old 1st September 2014, 06:16 PM   #9
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Quote:
Originally Posted by Eldam View Post
I bought a murrata RF 1:1 for one of my two SB Duet and lazy to implement it to an AB test (with ears)...
I hope it is DA101C

Quote:
Some designs do not use it with sucess as the Subbu DAC.
A lot of people don't have the knowledge to implement transformer properly.
A lot of people just don't care, all sounds the same to them.
But why are they building DIY audio stuff, if everything sounds the same???
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Old 1st September 2014, 06:26 PM   #10
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Huh, to find a different, maybe better sound...

I was thinking about Ethernet transformers, but they are designed for use with twisted pair differential signal and has additional inductors.

http://i.imgur.com/Mi8SW4o.jpg

How would You propose to properly implement PE-65612NL?
Probably most often will work at 44.1kHz, 48kHz or 96kHz sampling frequency...
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