75ohm to 110ohm Impedance Transformer?

[Maximus89]

My cheap DDC only takes USB to SPDIF/Toslink. I want to move over to balanced XLR AES/EBU, but not sure i want to spend the money for an expensive new DDC as my current one(a chinese dac with ddc that was modified by a tech) sounds better than the more expensive m2tech or denafrips i previously had. Would a 75ohm bnc spidf to 110ohm aes/ebu impedance transformer (along with a bnc to rca converter on my DDC end) degrade sound quality?

A quick online search shows Neutrik, and Canare make affordable impedance transformers, but no real in depth reviews or measurements anywhere.

 

[sergeauckland]

For short lengths of cable, say under 10m, you can just connect the unbalanced S-PDIF to the balanced AES-EBU XLR just as you would an analogue source. Join together XLR pins 1-3 and signal to pin 2. S-PDIF has exactly the same data as AES-EBU, and although the voltage level for S-PDIF is lower, I'm never known an AES-EBU receiver that wouldn't lock to the lower signal level.

One great benefit of digital is that it'll either work or it won't. There are no audio quality degradations possible, it either works completely properly or it won't work at all.

S.

 

[Maximus89]

For short lengths of cable, say under 10m, you can just connect the unbalanced S-PDIF to the balanced AES-EBU XLR just as you would an analogue source. Join together XLR pins 1-3 and signal to pin 2. S-PDIF has exactly the same data as AES-EBU, and although the voltage level for S-PDIF is lower, I'm never known an AES-EBU receiver that wouldn't lock to the lower signal level.

One great benefit of digital is that it'll either work or it won't. There are no audio quality degradations possible, it either works completely properly or it won't work at all.

S.

I suppose i was leaning more toward the jitter side of the question rather than "would it pass the 0s and 1's or not?" That's the degradation i meant. Would it introduce more jitter to the signal?

 

[mansr]

although the voltage level for S-PDIF is lower, I'm never known an AES-EBU receiver that wouldn't lock to the lower signal level.

The minimum signal level at the receiver is the same for both, 0.2 Vpp. AES/EBU transmitters have a higher level, up to 7 Vpp, in order to withstand higher losses of longer cable runs.

 

[mansr]

I suppose i was leaning more toward the jitter side of the question rather than "would it pass the 0s and 1's or not?" That's the degradation i meant. Would it introduce more jitter to the signal?

Don't worry about it.

 

[Maximus89]

Thanks gents. I feel more confident about giving it a go now, though the Japanese do pin 3 hot and that's the only thing left i have to figure out. Do i reverse phase on the dac? I think Acrolink, being Japanese as well, probably does pin 3 hot so it would be at the impedance transformer where i would get a different xlr pin configuration.

 

[mansr]

Thanks gents. I feel more confident about giving it a go now, though the Japanese do pin 3 hot and that's the only thing left i have to figure out. Do i reverse phase on the dac? I think Acrolink, being Japanese as well, probably does pin 3 hot so it would be at the impedance transformer where i would get a different xlr pin configuration.

Polarity doesn't matter. Bit values are encoded as the presence or not of a transition within a time interval, the direction making no difference.

 

[Maximus89]

Bought the impedance transformer and bnc to rca adapter. Got my expensive cable. Excited to hook it up. No sound output. BUT, i know it's not the transformer or cable or adapter. I've had a aes/ebu cable with a mutec in here before told him his cable didn't work, because i didn't get sound output out of it, but i did with spdif. It turns out i must have an issue with my AES/EBU input on my dac. No idea if it's broken or if it's just an early version? My dac is from 1992. The brouchure says minimum input 0.2v, 250ohm. I know this cable and xlr digital inputs are 110ohm now right? Is that the problem? Was 250ohm the standard back then and is there anything i can do to make it 110ohm?

 

[egellings]

If that transformer was not wound with oxygen-free copper wire, I am not even going to bother to stop by and listen!

 

[Speedskater]

Does it work without the transformer?
The difference between 75 Ohms and 110 Ohms is not a big deal for cables shorter than about 10 meters (30 feet).

 

[Maximus89]

Does it work without the transformer?
The difference between 75 Ohms and 110 Ohms is not a big deal for cables shorter than about 10 meters (30 feet).

I only have rca spdif and they work. My converter and the only way i can get music out of my computer is rca spdif or toslink. All work. ST works. Only AES/EBU has an issue and the previous time i thought it was the cable, i used both a mutec and a m2tech converter and it didn't work. I can't use this xlr cable otherwise. Will xlr to rca adapters work on both ends?

 

[Maximus89]

I have digital recorder i/o's, both rca spdif and AES/EBU. The RCA Spdif recorder input worked and output sound. The AES/EBU recorder input once again, no sound.

 

[sam_adams]

It would help if you would let us know what the brand/model of the DDC is.

 

[Maximus89]

It would help if you would let us know what the brand/model of the DDC is.

CM6631A? Dac portion is disconnected, only using it as usb to spdif. Modified by a tech, but as i've said a mutec and m2tech failed to produce sound on the AES/EBU and at the time, i blamed the cable. Now i know it's the dac. So now i need to see if it's worth getting a pair of 110ohm to 75ohm impedance transformers for each end + the bnc to male rca adapters. I already spent 60 on the adapters and 75 to 110ohm transformer and not to mention more than half a grand i spent on the cable itself. So even possibly pricey repairs + potential resale value hits if i have to replace the original connectors on this Accuphase DC-91- i may just have to sell the cable used and take a hit before even getting to hear it.

 

[Maximus89]

Polarity doesn't matter. Bit values are encoded as the presence or not of a transition within a time interval, the direction making no difference.

I spoke with an Acrolink rep who thinks i need to change the polarity of the xlr cables to match the Accuphase pin 3 + xlr input, but the thing is i've used american xlr's with pin 2 + on 3 different Accuphase units-but those were all analog i/o's including my current dac analog outputs-xlr cables work with the pin 3 + configuration on the dac just fine.
If you're positive polarity shouldn't matter with digital aes/ebu xlr in terms of sending the digital signal(This DC-91 dac was made with the matching DP-90 cd transport source which was also pin 3 + output). Then the only thing left to consider is defective xlr connectors or solder join on the xlr connector of the dac right? It just makes me wonder what are the odds, of all the connections on this unit, only the AES/EBU don't output sound, and it's not just 1, but 2 AES/EBU inputs that won't work.

 

[mansr]

If you're positive polarity shouldn't matter with digital aes/ebu xlr in terms of sending the digital signal

I'm certain it doesn't matter. In fact, the polarity changes from one sample to the next depending on the value of the last bit.

 

[sergeauckland]

I spoke with an Acrolink rep who thinks i need to change the polarity of the xlr cables to match the Accuphase pin 3 + xlr input, but the thing is i've used american xlr's with pin 2 + on 3 different Accuphase units-but those were all analog i/o's including my current dac analog outputs-xlr cables work with the pin 3 + configuration on the dac just fine.
If you're positive polarity shouldn't matter with digital aes/ebu xlr in terms of sending the digital signal(This DC-91 dac was made with the matching DP-90 cd transport source which was also pin 3 + output). Then the only thing left to consider is defective xlr connectors or solder join on the xlr connector of the dac right? It just makes me wonder what are the odds, of all the connections on this unit, only the AES/EBU don't output sound, and it's not just 1, but 2 AES/EBU inputs that won't work.

There is one distant possibility that I've come across only once. As part of the data stream, there is a bit which denotes whether the stream is 'Consumer' or 'Professional'. The audio data part of the stream is identical, but one of the status bits can be different. One (and only one) piece of equipment I've come across was set such that the AES-EBU input would only respond if the status bit was set to 'Professional' and would ignore any stream where the bit was set to 'Consumer'.

It's a long shot, but that is one possibility.

S.

 

[Maximus89]

There is one distant possibility that I've come across only once. As part of the data stream, there is a bit which denotes whether the stream is 'Consumer' or 'Professional'. The audio data part of the stream is identical, but one of the status bits can be different. One (and only one) piece of equipment I've come across was set such that the AES-EBU input would only respond if the status bit was set to 'Professional' and would ignore any stream where the bit was set to 'Consumer'.

It's a long shot, but that is one possibility.

S.

Well it does mention professional several times

Would any tech know how to change it from Professional to Consumer?