Digital Coax to XLR adapters?


Hi. I'm a newbie audiophile, so apologies if my question is naive.

Recently made some purchases on a "starter kit":
- Totem Acoustics Forest
- Music Hall 25.3 DAC
- NAD 375BEE integrated amp

The weak link in my system now comprises my sources: Sony CD carousel, Philips CR player/recorder, and Samsung DVD that can also play CDs.

My question: The digital outputs of the Philips CD and the Samsung DVD are both Coax. The DAC has only one digital coax in slot. But it has an unused XLR slot.

Is there such a thing as a Digital Coax-to-XLR converter? I have found XLR-to-RCA converters online, but I think those are for analog signals. Don't I need a special digital converter? Does one exist, and if so, can anyone recommend a good source?

Responses most appreciated!
128x128dquarasr
You shoul ask the folks at Music Direct, who I think sell the adaptors. or ask Cardas; they sell very good RCA/XLR adaptors. I don't see why the would not work. Just passing a signal, but what do I know. Just a dumb lawyer who thinks digital means pertaining to fingers or toes.

Neal
The input on your DAC is AES/EBU which is a balanced XLR connection, but intended for a digital signal at 110 ohms. Your coax input on your DAC and output on your CD player is a coax S/PDIF input, which is a 75 ohm digital signal. So no, you can't use a connector to adapt one to the other. They are very different connections and use different standards and protocols. You need to go coax to coax using a digital RCA cable (NOT an analog RCA cable). Perhaps there is a digital coax splitter you could find, that would allow you to switch between inputs, but I don't know much about that. Google is your friend. Or maybe someone else can chime in.
The input on your DAC is AES/EBU which is a balanced XLR connection, but intended for a digital signal at 110 ohms. Your coax input on your DAC and output on your CD player is a coax S/PDIF input, which is a 75 ohm digital signal. So no, you can't use a connector to adapt one to the other

BINGO .. also the Single Ended out's OUTPUT voltage may not be high enough to drive the AES's INPUT stage to full rating

But this should do the trick and kill two birds with one stone Monarchy Dip Classic

It will accept Optical .. Co Ax and AES/EBU on it’s inputs and it will output a De jittered signal on either Co Ax or AES balanced

Run one Co Ax to the Dac (present set up) and the other Co Ax to the DIP and take the Balanced output from the DIP to the Balanced inputs on the Dac ... I’d also run the OPTICAL out from the Sony CD carousel to the OPTICAL In on the DIP

What ever Co Ax and the OPTICAL feed you run through the DIP will get the benefit from the DIP’s jitter reduction circuit

So you have a home for your other Co Ax out .. can use your AES input on the Dac properly and get some Jitter reduction also

I think you can still buy the DIP Classic new from Monarchy for around $100

Actually, what you need is 75 ohm to 110 ohm impedance transformer. Get one of these: Canare BCJ-XP-TRB 75 Ohm to 110 Ohm Digital Audio Impedance Transformer. For the money, it's worth a try. Note that it wants a BNC connection on the coax in side, so you may need an adapter for that.
I used this transformer and it works (with Benchmark DAC1). Be careful with the 6MHz Canare transformer bandwidth since protocol requires always 64 bits per sample (32bit per each channel)

44.1kHz x 64bit=2.82MHz OK
96kHz x 64bit=6.1MHz OK
192kHz x 64bit=12.3MHz Not working

Protocol is pretty much the same but characteristic impedance and levels are different. Since you need to get from S/Pdif to AES/EBU you need to change characteristic impedance from 75ohm to 110ohm and increase voltage from 0.5V to 5V (active circuit or transformer required)

Bandwidth limit of 6MHz will also slow down transitions to about 27ns. It won't affect typical player that has about 25ns transition but will affect more expensive transports' faster transitions - for better or for worse. I wouldn't worry about it now since it is system dependent and effect are unpredictable. Transformer is cheap and also sold on Ebay where I bought mine. Be sure it is BNC to XLR and not the other way around (XLR on transformer has to be male). Use number Drubin provided to avoid mistake.
Excellent points by Kijanki, as usual. How did you calculate the 27 ns, though? If it were similar to a first order RC-type rolloff, for instance, the risetime and falltime corresponding to a 6 MHz bandwidth would be 0.35/6 MHz = 58 ns. Also, putting a bandwidth limitation corresponding to a 27 ns transition time in series with 25 ns I believe would result in risetimes and falltimes of about 37 ns, corresponding to the square root of the sum of the squares (I think :-)), which could very conceivably result in an audibly significant increase in jitter (timing fluctuations) with some DACs in some setups.

Another possibility to consider is shown here, a (two-way) S/PDIF to AES/EBU converter that utilizes active circuitry, rather than (or perhaps in addition to) a transformer. It would not require an RCA-to-BNC adapter, and is described as being suitable for applications up to 24-bits/96 kHz.

I have no experience with any of these devices, though, and no feel for the extent to which inserting the Hosa converter into the signal path might result in an increase in jitter (as a consequence of either its effects on signal risetimes and falltimes, or noise it may add to the signal, or impedance inaccuracy). Although the user comments that you will see posted at the B&H link by various pro audio people are generally very favorable, FWIW.

Another alternative, at considerably higher price points, would be certain "reclockers," whose purpose is to improve sound quality by reducing jitter in the digital signal. Some of them can accept S/PDIF inputs while providing AES/EBU outputs.
Apologies if my question is naive.
At this point in the thread it would seem to be well established that it is not :-)

Best regards,
-- Al
Al, you're right 58ns it is. I took fastest hypothetical slew rate corresponding to 6MHz being 1/6e6/2pi=27ns. It would be more realistic to take 1/3 of the cycle for -3dB attenuated signal. I'm not sure if 27ns in series with 25ns should be calculated as square root of the sums of squares but if it is we get SQRT(25^2+58^2)=63ns - very slow. It might be a very bad thing in a noisy system. Reclocker is always wonderful solution opening possibility of PC Audio server. My Benchamark DAC1 has reclocker built in reducing jitter effects making possible problems that transformer brought (jitter) inaudible.
To all, wow, what great responses. Yeah, I figured this wasn't just a simple "connection" adapter but also required some sort of format/signal modification from one format to another, which is why I asked here.

The responses were, frankly, bewildering, not because they were inappropriate but because my frame of reference is like a kindergartner sitting in an advanced calculus class.

"I think you can still buy the DIP Classic new from Monarchy for around $100"

Would it were true. List price these days is $249 per the website (thanks for that link; that's a perfect component for this situation). Not sure it's worth the investment for as often as I'd need to use the DVD through the NAD, though; at this point in time in my system's evolution I'd be happy to simply unhook one and connect the other. But that does not diminish my appreciation of the wealth of info provided here, most appreciated.