Is there any problem running an RCA coax cable (streamer output) to an AES/EBU input (dac), other than a difference in wiring connections in the connectors? Just discovered my dac’s BNC port, which I was planning to use for a streamer, was swapped out during an engine upgrade for a Toslink, without my having asked for it.
One is a balanced connection and the other SE.
1 Like
So no problem, just different wiring in one or both of the connectors, or is an adapter needed on the AES/EBU end?
It’ll work with most DACs, and it won’t hurt anything to try.
1 Like
Just the cost of a good cable…
What streamer and DAC are you trying to connect?
For starts, I’m likely to go for good quality low cost unit, such as the Wiim Ultimate, to see how subscription streaming works and how much I actually use it (I have a large music file collection and use it currently with an SSD plugged into a digital only modified Oppo 203) The dac is a Lampi GG3.
Lucas Domansky and those I know who’ve bought his LDMS server/streamer have touted spdif over USB. That jibes with what I’ve read over the years. That’s where my specific question comes from (in addition to having a favorite digital cable, the PAD Neptune). I don’t have an opinion from comparing myself, however, and LampiNA does now tout their USB as being superior. Given the unexpected change that occurred in input ports, I’m looking at my options.
in most cases it will just work.
a 75 ohm coax cable but with an xlr on one end works fine for me whenever i have need 
1 Like
or use the toslink input (assuming streamer has a toslink output) - free galvanic isolation and especially at 44.1/48 is rock solid.
plus, it uses lasers, man, ain’t nothin’ cooler than lasers
3 Likes
Admittedly I stopped trying different DACs some years ago, but until the DS DAC Toslink was always the worst-sounding input on everything I ever tried. The DS is (was?) special in its ability to just ignore jitter, which is Toslink’s major flaw.
As always though the only thing to do is just listen for yourself. At least these are really cheap options to compare.
1 Like
AES/EBU is a digital 110-ohm balanced input. A digital coaxial cable like 1694A is 75-ohm unbalanced. Using a PIN 1 shield ground and a PIN 2 center conductor hot wired to an XLR. This configuration eliminates the CMRR, Common Mode Rejection Ratio (we no longer have a opposite signal balance), that enable superior BER, Bit Error Rate.
There is nothing but problems created mismatching balanced and unbalance even past the input impedance. Why does it sometimes “work”. Because we have short leads and the signal strength still manages to get the message across with the increased noise (no CMRR) and return loss reflections (RL) for the impedance mismatch when using a RF level AES/EBU signal.
Pure ANALOG is a little different as we use a high impedance LOAD (immitates infinity resistance) so we don’t really have true RF “reflections” off the load like RF and just lose the balanced noise rejection…but that’s something that’s valuable to keep.
For all the perfection we want in our systems, this is not something I would do, a proper cable isn’t that expensive. So that’s the technical reason for not doing it.
It is always best to use the right cable for the above reasons, analog or RF.
Best,
Galen
1 Like
Thanks. The question wasn’t about the proper cable per se, but dealing with mismatched output-input between devices, given that the dac’s BNC input was eliminated. What I read is that in recent years some or many of the better quality dacs have substantially improved USB handling (noise, hopefully ground loop issues). From my perspective that’s fine, with the caveat that finding a USB cable at a medium price I like sonically is apt to be a trying process. I’ve been assuming Spdif because, in addition to thinking I still have a BNC port, I know from previous auditioning that the PAD Neptune (RCA) has the modest bit of warmth I like, in addition to other qualities. But it sounds like USB will have to be it.
The problem with USB is the poor ground differential in digital USB systems. You can use an Audio Quest FMV dragonfly type device to galvanically isolate the USB gound from the connected device. I use one from my PC USB cable to the DAC, for instance. That shuts off the RF noise and ground differential.
Here are a couple links that describes the problem and the solution. It aplies to our use of PC’s and servers in the audio domain as well.
Best,
Galen
1 Like
The context of my question was streamer to dac, no PC involved. My reading is that some dacs have dealt with the galvanic isolation problem, and more.
A USB port is a USB port and they all have the ground problems. “Some DAC’s”? Has yours? Do you know that? The solution is less than $100.00 to USB port ground differential noise. It isn’t the DAC, either it is the USB SOURCE port to the DAC. Stop it at the source as the saying goes. Why let the noise go down the cable where the interference inductance is the worst?
The attached educate the USB port noise problem in plain speak, and how ground differential is a problem for any server, streamer or PC. Use the right cable and isolate the grounds between devices is the solution.
Best,
Galen
I notice the examples in the second article are dedicated computers. Excuse my caution, but the other thing I notice is that the other end of the AQ FMJ is USB-B, which means that the USB cable to the dac would have to be B to B, i.e., a custom build. Given the seriousness of what you pose, that would seem to be a commonly offered build or recommendation among better cable companies, if not also offering their own isolator themselves. That’s not something I’ve seen, AQ notwithstanding.
One end is a USB-A male plug, on the opposite end a USB-A female connector. The other end of the cable that goes into the DAC is a “B”. This is a pretty common cable, A to B.
As far as the tech, not all situations are considered, but if you truly want to maximize the BER headroom, getting the possible USB ground isolation issue out of the way is a good start. This isn’t a made-up problem with complex digital stuff. The Egor’s lab demonstrates that in actual measurements and tests, the FMV works and the probem is demonstrated to be real. I can’t really help more than this.
Best,
Galen
2 Likes
Perhaps I misread a review. No harm giving the FMJ a try, although I’m not sure how much I can tell it with the current set up: SSD to Oppo via USB. The SSD is in a 3.0 case, while everything else is 2.0. But the run has worked that way with little if any delay, so maybe the FMJ won’t cause any problems. Thanks,
One thing I didn’t mention re ground loops and noise is that those have disappeared, as all my main components have either signal or chassis grounds, and so will any server/streamer I eventually get.
I’ve just heard from LampiNA, which not only sells dacs but also a streamer (and more thsn just Lampi’s through their import business). They’ve found no ground or ground loop issues of any kind with USB, which they recommend.
All systems no matter how good have ground loops because of the resistance of the wire(s) between ground points. It is a matter of how bad they are, and bad enough we label them Ground Loops (we can hear them in analog domain). Thus, the problem is guaranteed as a byproduct of the physics behind it. We manage it, we can’t eliminate it within the device. We can galvanically isolate the devices, though. That helps.
There are also multiple ground paths through devices that impact ground loops in front of a USB circuit. I take it we don’t want to read the two articles that explain all this very well?
1 Like