Impedance mis-match?

Hi Steve,

Preferably neither. Frankly, I wouldn't use those two components together. And as far as I am aware, a 50 ohm output impedance is non-compliant with the S/PDIF standards.

I see that the manual for the V-link model you are probably referring to does indeed indicate a 50 ohm output impedance, which is very surprising to me. And a quick Google search reveals a number of people expressing concern about the resulting impedance mismatch, along with some not very conclusive indications that it MIGHT be a specification error.

If there is no other choice my instinct would be to go with 75 ohms, so that the match at the receiving end is as good as possible, and given the possibility that the 50 ohm spec might simply be wrong. But which is best could very conceivably vary unpredictably depending on the length of the cable and the unspecified risetimes and falltimes of the V-link's output signal. Preferably, as I say, I would avoid using that component altogether.

Best regards,
-- Al

Edit: My response was composed before seeing ZD's. Great minds think alike :-)

Thanks guys - that was my thinking also

However, I do have these two components and they work extremely well together.

Perhaps it's a typo on the v-link spec? - I'll have to contact them

Perhaps it's the cables I'm using - which are far from standard 75 ohm cable specs

If you're interested in the cables I'm using I've posted details on Cheap Tweaks

02-19-15: Williewonka I don't know why this works - but it does...

It would be interesting to actually know what the scoop really is :-)

Chat Later

I would use 75 ohm cable, since reflection from the other end is possibly worse, as Al stated, but also because output RCA connector is not likely 75 ohm anyway.

I would use very short cable - as short as possible. Wire becomes transmission line when propagation time is longer than 1/8 of transition time. Assuming typical 25ns output transitions cable should be limited to propagation time of about 3ns, equivalent to about 2 feet (5ns/m). Since internal connections on both sides (including PCB traces) count I would limit it further to 1foot max. Otherwise I would use 1.5-2 m cable to ensure that reflections from the other end miss originating transition.

I use a V-link192 connected with a 75 ohm Wireworld Starlite 7 cable into a Wyred4Sound Dac1. Sounds better than my Esoteric UX-3 SACD player.

I'm using a v-link to a bifrost and have so for almost a year. It gets used about 40 hours a week. Never has faltered at all and sounds spectacular for the money.