As @garbz pointed out, wired digital interconnects are often transformer isolated to avoid ground loop issues. IIRC it's mandatory for AES/EBU in the transmitter, and for some versions of the spec in the receiver too, although someone better versed in these may correct me. You can see the transformer in the internal pics of the DAC-SQ3 or even the £16 Fun Generation UA-202. It's not quite universal - see the HifiBerry Digi+ Standard which has an unpopulated footprint for the transformer, or various PC motherboards - but it's certainly not unusual.May sound like a smoke screen until you witness one when trying to interconnect three or four different types/mixes of interfaces, including analog audio.
If you tell me again that ground loops don't exist (and/or "nothing of the sorts"), I shall ignore your comments. Cheers!
I currently stream music from a HTPC to a Denon AVR4600 (SINAD of ~99ish in pre-out mode) via HDMI. I've wondered about the potential improvement a D10 or similar would provide as a USB-Coax converter compared to HDMI. From what I've read so far, am I right to assume there is likely no discernable improvement to be had? Any other benefit to getting away from HDMI?I have measured coax input for some. Hard to generalize though. Here is an example:
There is no standard for this. You'll have the check the manual of your equipment. Tascam units seem to use 50ohm BNC but have a selectable termination resistance of none, 50ohm and 75ohm. Mutec seems to use 75ohm BNC predominantly with some devices providing both 75ohm and 50ohm outputs.is BNC 75 Ohms compatible with spdif 75 ohms ?
But not electrically, which is the entire point of termination. Now here's a question for you. Jitter is basically a non-issue in audio, so the terminations involved here become trivial. But is it still a trivial matter when you spend $4000 on a master clock source to improve something already imperceptible only to then hamper the effort by choosing the wrong one? I think when we're talking about the use of master clocks we've moved far beyond "going to be an issue", and are well and truly in the realm of "is it ideal"All BNC connectors are mechanically compatible. In this instance, the slight impedance mismatch isn't going to be a issue. I'd use whatever I might have lying around and not give it a second thought.
...on the other hand; it would not cost you oodles if you get rid of the "mis" part, as a good practice!...the slight impedance mismatch...
Uh, you can easily get 75 ohm coax, and BNC's that fit. (or buy it made up) $10ish bucks for "more perfecter". At that price, why not? OH, yes, that would be a regular RF cable, not Audiophile pricing....on the other hand; it would not cost you oodles if you get rid of the "mis" part, as a good practice!
Or offload the hi-grade hardware which relies on providing the best wordclock sync you are trying to achieve, while cheezing out on coax/RF signal integrity.
As always, YMMV.
You're missing something. To use a transmission line you need a constant impedance across the line. Having a 75ohm BNC plug mated to a 75ohm BNC socket doesn't help you if your cable is 50ohm, or your source is 50ohm.Uh, you can easily get 75 ohm coax, and BNC's that fit.
To be clear, I have both 50 Ω and 75 Ω cables with proper connectors of various lengths, and when practical I'll use the correct type. If buying a cable for a specific purpose, I'd obviously get the correct one too. Still, I won't hesitate to use mismatched cables if that's more practical and the use case isn't too sensitive. Audio related things never are.
You keep repeating that claim, yet you persistently refuse to give a single example of actual equipment that suffers measurably from this so-called problem.While the edge speeds in SPDIF are slow, which some may conflate with relaxed requirements for impedance matching, the voltage levels and hysteresis are also low, which does present the potential for jitter, which is not theoretical, but has been illustrated. If you have a new competent DAC, it probably does not matter, and given the limits of human hearing, in most cases it would not matter anyway, but there is still the potential for additional jitter with poor termination and the end result with some DACs will be < 16 bit performance.
It is nothing of the sort. Most semi-competently designed DACs will have transformer isolated coax inputs which far outperform crappy Toslink, or they simply galvanically isolate digital and analogue signals between the receiver and the DAC chips. And by outperform I mean in terms of a reasonable looking waveform at the receiver and also the liklihood of longer cable runs or cheap junk cables actually simply working.
The DAC-SQ3 which was used for this test is no exception.
You keep repeating that claim, yet you persistently refuse to give a single example of actual equipment that suffers measurably from this so-called problem.
No, this is a common trope that is repeated on audio forums but is incorrect.
Galvanic isolation of coax SPDIF is not perfect. First, there is the interwinding capacitance of the transformer to account for. The Newava S22083 has 15 pF from pri to sec. This is around 100 Ohms at 100 MHz.
Second, trying to galvanically isolate an interconnect that uses a shielded cable forces a compromise. Imagine you have a Class I appliance with metal enclosure. That enclosure is connected to PE as required for safety. When you add a BNC or RCA connector for your coax, you need to decide if it's an insulated BNC or one that connects to chassis. If it's insulated, you do still have isolation, but now you have an RF "hole" in your enclosure and you're bringing the coax shield into the to chassis through it. If it's not an insulated connector, that solves this problem but you have just defeated the purpose of the isolation transformer.
TOSLINK provides better isolation and there is no audible issue with the increased jitter. The only disadvantage is probably max cable length as you mention. I guess some transceivers don't work at 192 KHz either.
I am not sure on the technology as stated here. DACs buffer the data stream so the jitter is a function of the DAC clock, not the layer one transport. Think about it. It has to as R & L come in a serial stream! Now if some DAC implementation was so cheap it tried to lock a clock to the incoming stream, well shame on them. It will be all over the place and noise might effect it.This has nothing to do with the scenario here and what is tested. Jitter is created by the quality of transmission of S/PDIF over Coax in DAC-SQ3. The filtering is occurring in Topping DX3 Pro+ receiver/ESS DAC it has. It is not fed USB audio to care one way or the other in this testing.
I am not sure on the technology as stated here. DACs buffer the data stream so the jitter is a function of the DAC clock, not the layer one transport. Think about it. It has to as R & L come in a serial stream! Now if some DAC implementation was so cheap it tried to lock a clock to the incoming stream, well shame on them. It will be all over the place and noise might effect it.
So, yea the quality of the coax, optical and USB matter, but they are a function of the DAC execution, not the host. I wonder if that is why the JDS I just plugged in does sound smoother than the Schiit. Better clock. If we believe anything OEMs say, both these companies have talked about interface implementation being more significant than the DAC chip used. From what the recent measurements you have made on some DACs, they must have very very good clocks. One was even advertised to have an oven.
Is there another way to look at this? I have not torn into the schematics of newer DACs.
It's all fantastic info. But jitter seems not to be an audible problem in any real world implementations. Even Dacs scoring low SINAD are not doing so because of jitter.