Isolator for digital audio is needed in cases where coaxial S/PDIF digital audio link forms a ground loop in your audio system. Typically in coaxial S/PDIF connections the coaxial cable shield is connected to equipment cases. This arrangement easily creates ground loops which can cause noise problems in various places in audio system. A suitable transformer can be used to isolate the coaxial S/PDIF signal and avoid ground loop problems (other option is to use optical connection instead of coax). Here is the circuit of the S/PDIF signal isolator I have used:

ELFA catalogue product 56-550-55 “PE65612 Trafo dig.siirt.” is a tranformer suitable for isolating S/PDIF digital audio signal. The manufacturer for this product is Pulse Engineering and their product code is PE-65612.
Ratio: 1:1
Bandwidth: 100 kHz-55 MHz ±3 dB

Here is a picture of the S/PDIF signal isoltor I built (box open):


More information on S/PDIF and related circuits can be found on my SPDIF document.

Dear Author http://www.epanorama.net !
The excellent message, I congratulate)))))
Hi, since I found it very interesting and since I have on hand some of these transformers, can I have a more clear picture of the box, or at least an easy schematics of how to connect the 4 pins of the trafo, please? thanks in advance! Adolfo
Thank you for your feedback.
I add more information to the blog to clear out the details.
I just added a new circuit diagram drawing that shows the exact connection of the transformer I used in my ciruit I built. The RCA connector on the left connects to transformer primary and the RCA connector on the right the secondary. It ideal direction for the signal would be from left to right throught this isolator (although the circuit works also well on other direction).
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