Coax to BNC connection for digital


I one has a DAC with unused BNC input and a streamer with coax output, can a cable be made with appropriate terminations that would not sacrifice sonics?  
mesch
Yes.  I would suggest getting a BNC-to-BNC digital cable and then use a Black Cat BNC to RCA  adapter.  Those are the best adapters.  This configuration would actually be better then having a cable made with BNC on one side and RCA on the other side.
Hi Mesch,

To add to Auxinput’s response, just make sure that the input impedance of the BNC input and the impedances of the cable, the BNC connector(s) on the cable, and any adapters that are used are all 75 ohms, and not 50 ohms.

Also, if you already have a suitable 75 ohm RCA-to-RCA cable at hand, you might consider trying it in conjunction with an inexpensive 75 ohm BNC male to RCA female adapter, such as this one:

https://www.bhphotovideo.com/c/product/1024160-REG/remote_audio_app38_rca_phono_female_jack.html

Happy holidays! Best regards,
-- Al

I use the DH labs d750 which is terminated with rca on the transport end and bnc on the dac end.  No adapter necessary.   It is an excellent cable imho.  
https://silversonic.com/products/digital-cables/d-750/?_vsrefdom=adwords&gclid=Cj0KCQiA0ZHwBRCRA...
Blue Jeans Cable offers a couple digital cable options with BNC to RCA terminations... https://www.bluejeanscable.com/store/digital-audio/index.htm
Thanks all for the this information. You have answered mine main concerns, regarding having a cable made, if there were adapters, and the issue as to 50 vs. 75 ohms service. I do have 75 ohm RCA cables and will will most likely look for an adapter. 

Given the DAC has BNC, should I purchase a server with BNC output I would  then just purchase a BNC cable which I suppose would need be rated for 50ohms. 
Forgot to edit..my main concerns.

Happy Holidays to all!

Given the DAC has BNC, should I purchase a server with BNC output I would  then just purchase a BNC cable which I suppose would need be rated for 50ohms.
Hi Mesch,

The output impedance of the server, the input impedance of the DAC, and the impedance of the cable should all be the same, or there may be adverse sonic consequences that are equipment and cable-dependent, and that are essentially unpredictable.  BNC outputs, inputs, and cables used in digital audio applications are often 75 ohms, but are 50 ohms in some cases.  It would definitely not be good practice to connect a 50 ohm output to a 75 ohm input, or vice versa, although in some circumstances doing so **might** happen to provide reasonably good results. 

Best regards,
-- Al


Thanks Al. The DAC I have purchased, however have not yet received, is the Mirror Audio Tubadour III. It has a BNC input along with USB, toslink, and coax. Currently the coax will serve my CD transport, toslink my DVD player, and thinking if I get a server I will use the BNC. I will verify the impedance for the BNC connection for the DAC and find a impedance matched server, when and if I follow that route.  
As an additional thought, I could use a coax output from DVD player with RCA cable and a RCA/BNC adapter as opposed to a toslink cable. Thoughts anyone?
That should work well, Mesch, assuming the BNC input is 75 ohms (as is likely) and not 50 ohms.  Also, it would be preferable to use an adapter specified as 75 ohms, such as the one I linked to earlier.

Best regards,
-- Al

Thanks again Al for your help! That said, I am embarrassed in that I was mistaken about the additional input being BNC when in fact it is AES. My only excuse for my confusion is that I haven't received the DAC yet, a poor platform indeed. 

So I now must explore the subject of going from a coax RCA
 output to an AES input. 
I still can't believe that in my mind I replaced the AES outlet available on the DAC with a BNC one. AT 70 I feel I am in good physical shape, however my mind may not be keeping up.  

After some exploration I believe I am best off looking for a streamer/server with AES output and use appropriate 110 ohm XLR cable. This will be a 'down the road' investment. 
Actually some equipment provides an AES/EBU interface on a BNC connector, with a 75 ohm impedance!

From this Wikipedia writeup:

AES/EBU can also be run using unbalanced BNC connectors with a 75-ohm coaxial cable. The unbalanced version has a maximum transmission distance of 1000 meters as opposed to the 100 meters maximum for the balanced version. The AES-3id standard defines a 75-ohm BNC electrical variant of AES3. This uses the same cabling, patching and infrastructure as analogue or digital video, and is thus common in the broadcast industry.

Best regards,
-- Al


Well thanks again Al!  I really appreciate the time you have offered me on this.  I dare chance some more. 

The DAC am purchasing has the AES/EBU input that I likely will want to use. Currently I have both a DVD player and a CD transport with optical and coax SPDIF outputs. I also have two 1.5 meter 75ohm RCA cables available for use. I would prefer to use these cables between both the DVD player and the CD transport and the new DAC to avoid use of the optical connection.  Obviously this is no problem for one of the two disc players however the other will have to be connected to the AES input on the DAC. 

It is the impedance issue that has me confused. I know that a XLR microphone cable lacks the proper impedance for digital use. AES when balanced is 110ohms as I understand it. I believe with my new DAC I would be using a cable in unbalanced mode at 75ohms. I guess I need to verify this with Audio Mirror. 

If one has an 75ohm RCA cable can one fit a male RCA to male XLR adapter for my needs?  How does the impedance of the adaptor affect this? Or, based on the first sentence of the wikipedia report, can one use a BNC/AES adapter at the DAC input if one has a 75 ohm RCA to BNC cable? 
Hi Mesch,

My reference to the fact that some equipment (mainly some pro equipment) provides a 75 ohm AES/EBU interface on a BNC connector was a lighthearted response to what appeared to be your not very serious reference to the possibility that your "mind may not be keeping up," for not having correctly recalled the kind of interface that is provided on the DAC. :-)

To connect a 75 ohm S/PDIF output to a 110 ohm balanced AES/EBU input you would need a device such as the following, as well as a 110 ohm balanced cable to connect the output of this device to the 110 ohm AES/EBU input:

https://www.bhphotovideo.com/c/product/395533-REG/Hosa_Technology_CDL_313_CDL_313_Data_Link.html

Using simple adapters to connect an unbalanced 75 ohm S/PDIF output to a balanced 110 ohm AES/EBU input **might** work in terms of functionality (i.e., it may play music), depending on the specific equipment, but it would be very unlikely to be sonically optimal.

Best regards,
-- Al
Al, I am slowing down to allow my mind to keep up. :-).  I have decided that I will hook up the CD transport via RCA, and the DVD player via toslink and reserve the AES input on the DAC for a server/streamer should I purchase one.

I began a search for adaptors and in that search I came across the data link box you provided a link to. Given that I only use the DVD player for video I have decided that toslink optical will be the best approach. A single quality glass optical cable can be had at the price of this box.

Thanks once again for your help. Have a happy New Year!
Sounds like a plan!  All the best to you and yours for the new year.

Best regards,
-- Al