Splitting Signal to Multiple DAC’s

If you are using SPDIF with BNC coaxial connectors, you can use a 75 Ohm video coax and use a BNC TEE connector on each input.  This will result in the passive connection, a very common way to do it.  However, this is a 75 Ohm terminated line, so each of those inputs will have a 75 Ohm resistor shunting to ground,  When you get three of them in parallel, you no longer have a perfectly terminated transmission line and you will get reflections up and down the line.  To avoid this, you must use an active SPDIF buffer so that the input is terminated in 75 Ohms and each buffered output becomes a separate 75 Ohm transmission line.  If this was an analog video signal, you could use a one to three video transformer and split it that way, while each line remains at 75 Ohms, there is a resulting loss of power in the three outputs.  One can use this approach with digital signals, too.  Here is an example of one, but uses F-Series connectors. https://smile.amazon.com/dp/B01M34OZ2S/ref=redir_mobile_desktop?_encoding=UTF8&aaxitk=f91e24525356a86d19934c46c0666b83&content-id=amzn1.sym.53aae2ac-0129-49a5-9c09-6530a9e11786%3Aamzn1.sym.53aae2ac-0129-49a5-9c09-6530a9e11786&hsa_cr_id=5958461450701&pd_rd_plhdr=t&pd_rd_r=444a4663-e0fe-4006-a7f1-73283e0ccb4b&pd_rd_w=RCQpJ&pd_rd_wg=Ev1Dl&qid=1665513757&ref_=sbx_be_s_sparkle_mcd_asin_0_img&sr=1-1-a094db1c-5033-42c6-82a2-587d01f975e8

If you are using SPDIF with Toslink optical cable, then you must use an active buffer - splitter, as there is no real way to split the optical signal into three and still have good optical signal quality.  Do note that TOSLINK optical cable has a 10 dB loss every meter, so if you need a long connection, then this is probably not a good solution unless the buffer is designed to handle long optical cables.  Likewise, don't increase the optical signal level and then use a short optical cable, as you will most likely overload the input circuitry of the receiving end.  It is wise to read the instructions and follow them!

There is a very good discussion of SPDIF here: 

A good quality SPDIF active splitter with specified jitter should do the job for you. If you are a decent DIY'er,  you can get some useful information here: http://www.hardwarebook.info/S/PDIF_output

 Hope this helps....

Robert

@spatialking-

Hello Robert- thank you for the response. When thinking about this early on I thought about giving this device a try. This is pricey but not outrageous when considered to other active splitters out there. 
FYI- just to clarify I would be using 75 Ohm BNC connectors from Naim Uniti Core to various coax inputs on the DAC’s. No Toslink.

If you don’t mind I’d be interested in your opinion on this unit as it pertains to your explanation above.

https://www.sonifex.co.uk/cmaesb3/cm-aesb3.shtml

Thanks!

Correction- meant to say “when compared to active splitters”

Very interesting reading from @spatialking- getting more into it seems as though clock issues with the SPDIF data stream with increased jitter/distortion potential makes this not so simple (at least from my perspective). Sounds like the answer may be along the lines of this-

https://www.mutec-net.com/product_mc-3-plus-usb.php#data

@bruce_philly 

Hello-

I just came across a thread you started 5 years ago where you mention using a Mutec 1.2 as a throughput device to stream your music playback to multiple DAC’s and CD player. I’d like to ask if you’re still using this device and if so how well has it been working for you? Have you changed equipment/configuration since starting the thread? 
As you can see from the subject of this thread I’m trying to find the best method of distributing a single source to three separate DAC’s. Any insight you can provide would be appreciated.

Best-

Designsfx

@designsfx 

Hi there, the Sonifex is the transformer splitter I told you about.   The only problem with this approach, if it is a problem, is there is a loss of power in the signal, so you "may" have a loss of fidelity in the digital signal.  Fidelity here means the difference between a "1" and a "0" becomes blurred.  This is where EYE Diagrams and BERT testing will show if this is a problem.  You can Google this to find out what I am talking about if you are interested in that detail.   Clearly, the higher the digital frequency then the more likely this is to occur.  They didn't specify the loss factor in the unit but they did say 100M of coax at 96 KHz, so use that as your guide.  Do make sure your cable is rated 75 Ohms, most video cables are 75 Ohms, so use a good one. 

Note that in a properly terminated 75 Ohm line, the source, the coax cable, and the receiving unit must all be rated at 75 Ohms.  In spite of what is often advertised, RCA jacks can't actually achieve a 75 Ohms impedance, but they can be close.   BNC's are not a problem for 50 or 75 Ohm lines. 

An active device doesn't have the loss factor since it drives each output independently of the others, as each output is buffered.  However, they are more expensive, require power to operate, and overall may not make an improvement in your system over the transformer approach.   So, if you can, experiment and decide for yourself.  

@spatialking -

Thank you again for your advice on this- it’s really been helpful. Quick background with Sonifex- I made an inquiry on their devices earlier this year, they make both active and passive. I didn’t care for their active SPDIF distribution device as all connections are RCA and their sales dept couldn’t comment on the the approach to buffering.
The transformer based passive unit seemed like the way to go but I held off purchasing because I didn’t understand if the signal loss would be too high due to the fact that it was designed for AES 110 ohm applications. I like the idea of the passive though. I asked if Sonifex’s engineers could perform a quick test with SPDIF over BNC but they declined as “it wasn’t worth their time for a single unit sale”.

At this point I like the thought of using the Mutec 3+ USB as it seems to be of higher quality, offers a selection of different outputs and also offers an excellent word clock (at least from what I’ve read). I’m not in a hurry with this so I’ll do a little more research before throwing money at it. Again- thank you for the time and the great advice.

Best-

Todd

You could use This and if your DACs don't have AES3 in use These. The reason this type of splitter mainly uses AES3 is because they're used in professional situations. 

@djones51-

Hello and thanks for the shortcuts. I spoke with the folks at Henry sometime ago as this was one of the first distributors I had seen. These are actually made a few minutes from where I live.

The question with this one comes back to the signal voltage between SPDIF and AES as SPDIF is lower coming into the device. Not sure of what actually ends up leaving and/or if it’s too low or higher than what the DAC’s receiver is wanting. 

Have you tried this product for this application in the past?
 

These are used as impedance transformer to take the output from  the Henry 110 Ohm to 75 Ohm as all outputs on the Henry are 110 Ohm. You would need one for every DAC that doesn't have AES3 inputs. I've not used this product but have used Hosa products to change or split digital signals.