Thursday, August 21, 2014


For a while I debated about whether to change the connector of my SPDIF line from kitchen to living room that now carries high rez audio from my Mac/Amarra and BDP-95 to the main system.  This line uses all RCA connectors on the cables now.

This line is particularly complicated for other reasons, when connecting to the Mac.   It works, but I now go through two levels of optical/coax conversion.  First, a very fine Inday Toslink splitter splits the Toslink output from the Mac into 4 Toslink outputs.  This Inday active splitter has always worked perfectly, whereas passive splitters never work.  From the split outputs, one goes to kitchen receiver, another goes to a DAC to provide analog to my hard drive recorder.  The third gets converted from Toslink to Coax via another very fine M-Audio CO2 converter.  As I explained previously, this combination of splitting and subsequent conversion to coax requires two levels of optical conversion (or 4 levels if you count both the optical emitters and the receivers).  It also goes through at least one transformer for the coax (in the CO2).

With all that conversion going on, it's a wonder that it works at all, but in fact it has always worked perfectly, as far as I can tell, though I worry about jitter.  What did not work very long was a different converter I got to split one Toslink to two Toslinks and one Coax.  I had lots of problems with that converter, then after I did get it working, it stopped working after one day.  So back to the Inday Toslink splitter, and the two levels of optical conversion, which bother me but always work perfectly.

Well I figured I could optimize this a bit by trying to make the coax connection better.  Currently that is very complicated.  From the CO2 I run a 12 foot budget video cable from spare box (vinyl cable with stranded wire--about the same as Radio Shack's lowest grade AV cable from 2006) to the kitchen connection panel.  There it runs through an RCA to F adapter, into the panel, where it then runs through 50ft of Belden Precision Video cable.  In the panel in the living room, there is a second RCA to F adapter, followed by two short lengths of Monster Video 3 cable joined with an old RCA barrel adapter.  This is what stuff in the real world looks like.

One way to make the connection better would be to eliminate as many RCA connections as possible, particularly the ones that must go through those questionable impedance RCA-to-F adapters.

The original plan for this SPDIF line was that it would only provide data from the Mac.  Then I would simply get a cable with RCA connector on one side (to connect to the CO2 converter coax output) and F connector on the other side (to connect to the F connector on the kitchen patch panel).  In one fell swoop I would be replacing the low grade 12ft video cable, remove one RCA connector, and remove one RCA-to-F adapter which might be even worse than just one RCA connector.

But once I started feeding the SPDIF line from both Mac and Oppo, I needed a connection which would be easy to change.  Screwing and unscrewing F connectors is a big pain.  For awhile, I looked for SPDIF switches, but there's hardly anything like that available and often it is way overcomplicated with re-clockers and the like.  So back to just using the patch panel as a patch panel, and changing the cables to switch the playing device.  So then back to finding a good connection for patching.

On a lark, I looked for a push-on BNC connector.  Sure enough, Neutrik makes a special push-on BNC connector that was intended for patch panels.  It appears that I could special order a cable with this connector on one end through Markertek, as they are a Neutrik dealer.  The I could get (and already did) a BNC to F adapter for my existing patch panel.

That might be an optimal solution, but I wondered if even a push-on BNC might get a bit bothersome after awhile also.  One thing about RCA connectors is that they ARE easy to plug and unplug.

I also realized I was not seeing the big picture.  I could get just as much benefit by replacing the cable in the living room with one having F connector on one end and RCA on the other.  That would also eliminate the need for the F-to-RCA adapter in the living room, as well as the barrel adapter.  And all this business about impedance matching in the coax line is probably insignificant compared with the two levels of Toslink conversion.

So, for now, I've decided to stick with RCA connectors in the kitchen, where I must change the cables often.  I ordered and have now received from Blue Jeans Cable a 10 foot Belden 1505 with RCA on both ends for the Mac-to-Panel connection.  I used that cable to verify that a 10 foot cable would also be correct for the living room, and I will order that second cable with F connector on one end.

I've got a new plan for the Toslink splitting.  I'll use two (now out of production) M-Audio CO2 converters in series connected together with coax.  It's hard to know if that would actually be better than the current setup though.

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