SPDIF RCA phono to male AES/EBU XLR

[wilkinsi]

I have a synth with a coaxial RCA phono output, which can have its format changed to send an AES signal instead of SPDIF. I want to connect the synth to my AES/EBU interface but don't know the correct impedance the cable should be. It would also be handy to know which pins are soldered to which wires. Help greatly appreciated.

[nickrose]

I would just plug it in to the SP/DIF – should work OK.

[wilkinsi]

The only way is a cable with RCA on one end and XLR on the other. The problem is I don't know for definite what impedance the cable needs to be.

[nickrose]

AES is 110 ohms, SP/DIF usually about 75. Not critical unless the cable is long.

Connect pin 3 of the XLR to ground on the RCA, pin 2 to hot. Or the other way round – it will work either way.

[wilkinsi]

Thanks. Is there a set impedance per metre guideline? At what length does the impedance become important? Or rather, is there a "x" metre = "x" ohm conversion rate?

[nickrose]

I did transmission line theory at University, but it was a long time ago. Impedance for a cable is constant, and not affected by length.

The issue is more that problems caused by mismatches increase with longer cables.

I think you are worrying too much – do what you think is right, and worry about problems only when they occur. Example – AES specifies 110 ohms, but most people use mike cables – who knows what the impedance of a mike cable is ?

[wilkinsi]

Thanks for the reassurance

[wilkinsi]

Unfortunately, it didn't work. No audio full stop.

[wilkinsi]

Had the cable redone – got audio buried in digital clipping. Please, for the novice that I am, post a diagram stating which pins should be connected at both ends.

[nickrose]

AES is symmetrical, meaning it can be connected either way. Try connecting pin 1 and 3 to ground, and pin 2 to hot.

[wilkinsi]

I'll try that. Meanwhile, I connected SPDIF RCA from the EMU to the Eclipse, and the same problem occurs – its the clock of the EMU that's at fault.

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