[minimus]

I am looking for a way to connect my DAC, which has an XLR AES/EBU digital input, to my source, which has an RCA digital out. Does anyone know of a cable manufacturer who makes a single digital cable that is terminated on one side with an RCA connector and on the other side with an XLR connector and addresses the impedance difference between XLR (110 ohm impedance) and RCA (75 ohm impedance)? Morrow makes a digital cable that can be terminated with an XLR on one side and an RCA on the other, but he doesn't know how it addresses the impedance mismatch, only that no customers who have bought them returned them, suggesting to him that they must work OK.

Any suggestions would be much appreciated.

 

[poo]

I am using a DIY cable like this for my DAC1 USB - XLR out of DAC1 into RCA, not sure about a 'manufacturer' as such, but many (or most) of the cable companies who advertise here would make you one.

 

[Jon L]

Digital is totally different from analogue. To convert AES digital signal to spdif, you need a special converter, usually using impedance-matching transformers like this one.

Studio Hub MatchJack Adapters and Cables at Markertek.com

 

[NightOwl]

Since your source uses a digital rca out, you should use a 75 ohm cable to maximize your source's signal. Even this is not perfect since it is physically impossible to make an rca jack or connector that is 75 ohms. Most measure at about 50 ohms. A true 75 ohm connector would be a BNC or F connector. In any event, Canare has a good digital rca connector as shown in the link below. I have also read that the tiffany style connectors from Vampire measure fairly well.

Take Five Audio - Canada's Online Source For High-End Audio, Parts and Accessories - Canare RCAP C4F 75 Ohm RCA

I'm assuming that the input in your dac is balanced. If it isn't then ignore the following since the difference between a 75 ohm cable and a 110 ohm cable over a normal run will be very small at the dac end.

If you are sending an unbalanced signal to a balanced input, then this will have more effect by the potential introduction of noise into your dac than the impedance of the cable would. One way around this is to add a balun (or transformer) to the cable near the balanced end. This would create a quasi-balanced signal. This is probably more trouble than the potential benefit since you are already compromising the signal.

My suggestion would be to try a 75 ohm cable with an rca on one end and an xlr on the other as made by Morrow. It should work fine. If you get rf noise, you could add a ferrite choke at the xlr end. This will raise the impedance of the cable and help filter out rfi, although I don't think it will be necessary.

 

[minimus]

All,

Thanks for the advice, especially NightOwl. I think I will try the Morrow cable, since he offers a 60-day trial period.

 

[minimus]

Just as follow up for future reference (if anyone needs to find an XLR AES/EBU to RCA digital cable), the Morrow digital cable works fine with my DAC. Mogami also makes a similar cable, sold at B&H.

 

[krmathis]

Sure! Just buy or build a cable with RCA in one end and XLR int he other end.
Works fine, as long as your transport and DAC have the needed connectors.

 

[poo]

You really don't bother paying any attention to what's written in a thread before you post do you krmathis?

I can't imagine having a conversation with you... purple monkey dishwasher indeed!

 

[les_garten]

So there was not format conversion needed as suggested in one of the other posts here?

Les

 

[les_garten]

Hi,
Ohhh, which DAC are you referring to, the Northstar?

Les

 

[boomy3555]

an RCA plug and an XLR plugs are not availlable in digital or analog. The only thing that would be digital is the signal generated and recieved at the other end. The standard digital cable is simply shielded coaxail similar to cable tv. I said Similar so don't bite. So Headphone Addict is exactly right. It's just a matter of soldering an XLR to one end and an RCA to the other end of a coaxial cable. The hard part would be knowing which of the three or four XLR connections is which. RCA is simply positive and negative

 

[les_garten]

Quote:

Originally Posted by boomy3555 /img/forum/go_quote.gif an RCA plug and an XLR plugs are not availlable in digital or analog. The only thing that would be digital is the signal generated and recieved at the other end. The standard digital cable is simply shielded coaxail similar to cable tv. I said Similar so don't bite. So Headphone Addict is exactly right. It's just a matter of soldering an XLR to one end and an RCA to the other end of a coaxial cable. The hard part would be knowing which of the three or four XLR connections is which. RCA is simply positive and negative

Learn something new each day.

AES is basically the "Pro" version of S/Pdif if I am reading Wiki correctly. I guess an issue may be that AES Equipment expects 110 ohms and S/Pdif equipment expects 75 ohms. If you data can get thru the Impedance mismatch and Balanced versus unbalanced, it apparently will "work".

.

 

[NightOwl]

Quote:

Originally Posted by les_garten /img/forum/go_quote.gif Learn something new each day. AES is basically the "Pro" version of S/Pdif if I am reading Wiki correctly. I guess an issue may be that AES Equipment expects 110 ohms and S/Pdif equipment expects 75 ohms. If you data can get thru the Impedance mismatch and Balanced versus unbalanced, it apparently will "work". .

S/PDIF is an offshoot/adaptation of AES/EBU (which is the original professional digital standard). It is said to have been designed as a cheaper method of implementing that data transfer protocol in consumer equipment. Coaxial cable instead of twinaxial or twisted pairs. BNC (still expensive) or RCA connectors instead of XLR. Optical came along later.

The advantage of matched impedance is that maximum electrical energy will be transferred from the source to receiver. Because the shield is also part of the signal path (in coax cable) any rfi picked up is also transmitted down the cable. If the impedances are matched, the electrical energy and rfi is usually fully drained into the receiver. By having higher impedance at the receiving end, not all the rfi may be dissipated and the surplus will be bounced back up the cable. Because the source impedance is lower than the receiving end, it's usually sent back again. This can cause "reflections" and, in a worst case scenario, can set up standing waves in the cable (highly unlikely in this application although there have been reports of problems with some older tube amps).

What sometimes happens (and may not even be noticeable as it's much more of a problem in video, think "ghosting") is that your signal will have a little less gain and a little more noise.
Since a balanced signal uses a different method of noise rejection, then sending an unbalanced signal may introduce some noise into your balanced input as well as losing the benefit of balanced (except for the better connector). In reality, and as I said in my earlier post, these are problems more in theory than in practice. I wouldn't worry about them unless they actually crop up.

 

[is2us]

Sorry to bump this, but what about this for a solution?

Canare BCJ-XP-TRB IMPEDANCE TRANSFORMER PLUG FREE SHIP - eBay (item 110329428038 end time May-21-09 14:52:59 PDT)

You can get an RCA/BNC cable and use this adapter.

 

[les_garten]

Quote:

Originally Posted by is2us /img/forum/go_quote.gif Sorry to bump this, but what about this for a solution? Canare BCJ-XP-TRB IMPEDANCE TRANSFORMER PLUG FREE SHIP - eBay (item 110329428038 end time May-21-09 14:52:59 PDT) You can get an RCA/BNC cable and use this adapter.

Except that it is BNC on one end and XLR on the other. Does the BNC work for you?

.