Show me, please. This idea keeps being trotted out, yet I have never seen a shred of evidence suggesting that it poses the slightest problem.
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Study: Is I²S interface better for DACs than S/PDIF or USB?
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So much of the dialogue here can be summarized with that pithy description.
audio2design
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It's not an "idea", has been shown many times in the past, i.e. like 10-20 years ago, but is not as big an issue now because most DACs are pretty good at jitter rejection. I have seen a combo at an audiophile friend that would drop out when first turned on, cable was electrically okay, but obviously issue with the implementation (SIM DAC, can't remember what the CD transport was). Once it warmed up, the issue would go away. Changed to a 1/2 meter cable, no issue. 2 meter cable no issue. I actually scoped that one out of curiousity.
Do the math, it is absolutely a very feasible occurrence. I am sure it is raised as an issue more often than it is, but it absolutely happens and given all the crap expensive low tech DAC implementations out there, would not surprise me at all.
So show me a real, replicable example.
audio2design
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Really, do you hear yourself? I am going to go find equipment I had access to 10 years ago (and or I am going to waste time recreating today), to show you something that is pretty obvious to those skilled in the art, just to accomplish what? To try to impress someone and convince someone who does not appear to understand the issue? It is a digital transmission, with slow edge speeds, with connectors that are not impedance controlled in many implementations, with a cable length ideal for reflections to cause issues .... and you are questioning whether this "can" cause an issue.
Purely because I have the link bookmarked, you can have this:
A Transport of Delight: CD Transport Jitter Page 4
After measuring the first two products (the PS Lambda and the Panasonic SV-3700), I went back and repeated my measurements to make sure the analyzer was giving consistent results, and that my test setup was correct. When I remeasured the SV-3700, I got about half the jitter than when I first...
www.stereophile.com
Say what you will of John Atkinson's conclusions in his writings, he is consistent in his methodology and to that end, the jitter measurements are not really disputable. These levels of jitter in a modern properly designed DAC, or even one with most any modern DAC chip won't be audible. However, have you seen some of the crap (NOS DACs) that twaddle around claiming high end? Absolutely can see them not dealing with this adequately.
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I understand the "issue" perfectly well. Try as I might, however, no cable abomination I've concocted has had any measurable effect on the jitter at the output of even the cheapest of receiver chips.
audio2design
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And yet Stereophile was able to clearly measure it ....
Are you talking chips properly implemented by you or others at ADI (who had a clue what they were doing) and used in a lab environment ... or real world crap that gets designed?
I'm talking about chips by e.g. Cirrus as used in $5 DACs from China. Any jitter from cable reflections will be above the PLL corner frequency and thus a non-issue.
audio2design
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I see the issue in how you are approaching this and why you may have the belief you have.
You are approaching the jitter as a purely random event. However, reflection induced "jitter", and perhaps that is a poor word to use in this case is more like a clock teetering on a sharp peak. Mainly it stays on the peak, but then it falls off the edge a bit, which could be one clock off, or it could be several in a row, and suddenly you are getting in the range where the jitter attenuation is not that great. Cypress doesn't even spec jitter attenuation out past what, 100KHz, where it is about 10db and it rapid drops to 0 below that frequency.
Now add in some electrical noise from a poor implementation out in the great consumer wild, a touch of power supply noise, some coupling into the signal from EMI caps, even a small bit, and those reflections at inopportune times can do strange things.
The Stereophile article was made in 1993? Old, but we most certainly had SPDIF receivers with PLLs with low corner frequencies back then. The jitter measurements are sub-20KHz in the article.
This is what reflections caused by RCA connectors actually look like:
Does anyone seriously believe that those tiny blips are of any consequence whatsoever? They're not even anywhere near the zero-crossing.
Those measurements seem to be done on the S/PDIF signal itself, not the recovered clock. As such, they are only of interest to someone designing a clock recovery circuit. For anyone else, they are meaningless.
audio2design
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This is what reflections caused by RCA connectors actually look like:
Does anyone seriously believe that those tiny blips are of any consequence whatsoever? They're not even anywhere near the zero-crossing.
Those measurements seem to be done on the S/PDIF signal itself, not the recovered clock. As such, they are only of interest to someone designing a clock recovery circuit. For anyone else, they are meaningless.
Not sure what you are measuring, but that is a rise time of perhaps 3-5nsec. SPDIF is typically somewhere near 25nsec, but I have seen more and less. Of course your reflections are not near the 0-crossing. Where are you measuring? That is an exceptionally well matched to 75R connector assuming you launched with 75R characteristic impedance and received with the same. That looks like about a 5% mismatch, not atypical of RCA, though there are some actual impedance matched RCAs out there ...
That's showing the far end of a cable driven by an S/PDIF source and terminated into 75 Ω. The connectors are something generic unbranded.
If you want to convince me there's a problem, point me to a well documented (i.e. not Stereophile) experiment from a trust-worthy source (still not Stereophile) or describe something in sufficient detail that I can replicate it myself.
Lots of great info in this thread. My biggest issue with USB implementation with streamers running to DACs is connector compatibility—on many streamers such as SMSL’s DP5, the USB Audio output is USB B, which is also the INPUT connector for USB audio on most DACs. Finding a decent quality USB B to USB B cable hasn’t been easy for me.
Ifi’s Zen Stream has a USB A output to connect to the USB B output on my Topping D90se and those cables are easy to find. Why on earth a universal standard USB A output for streamers hasn’t been adopted, if DACs are going with USB B, is a mystery to me…
Ifi’s Zen Stream has a USB A output to connect to the USB B output on my Topping D90se and those cables are easy to find. Why on earth a universal standard USB A output for streamers hasn’t been adopted, if DACs are going with USB B, is a mystery to me…
Have you tried using a converter instead?
10 Pieces 5 Pin OTG Adapter Converter USB Male to Female For Computer Tablet Pc Mobile Phone: Amazon.co.uk: Computers & Accessories
Shop 10 Pieces 5 Pin OTG Adapter Converter USB Male to Female For Computer Tablet Pc Mobile Phone. Free delivery and returns on eligible orders.
www.amazon.co.uk
The explanation is simple, USB-B aren’t outputs, they are inputs. USB-A are often there to support external storage only, not for external DACs. RPi based streamers can usually output to external DAC via USB, the Zen Stream can as well, perhaps it’s built on n RPi, not sure.
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It’s not about the direction of data transfer. One end is a host, the other is a device. By convention USB-B connectors are used on the device end, hosts use USB-A. Not every host supports USB audio device class, but they can support mass storage which is what external discs are.
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Not only that, I have the latest firmware loaded on the DP5 and cannot get consistent playback via USB or iiS. The latter has a bit better stability but I still get zero sound output for quite a few files of differing sample rates. No audio with DSD 256 at all even though it shows as playing and my Topping recognizes the file and sampling rate. Same with several 96khz FLAC files.
The deal breaker is this freakishly alarming, explosive “pop” that brandishes my headphones when switching between files of differing sample rates. I’m sending this sucker back and sticking with my Zen Stream—it may not have the nice GUI or LCD screen but it’s rock solid stable and plays nice with anything—and I think it sounds superior as well.
I can’t seem to warm up to SMSL. They cut corners and their manuals are inscrutable. I doodled with the m400 and its cousin the Loxjie D50 for as long as I could tolerate them before returning them for a Topping D90se and a Gustard x26 pro and I feel no uneasiness having these in the chain like I did with the others.
If anyone has any updates on this popping issue with the DP5 or the SD-9, or experience with either the Cambridge Audio CXN v2 or Cocktail Audio N25, please do share?
Well I could, but I shelled out some big bucks for an Audioquest Coffee USB cable (with full acknowledgment of the controversies) and it feels a bit queasy to plug that into a cheap adapter. I’d rather stick with my Zen Stream and go without the SMSL’s graphical interface—I don’t need the DAC in the DP5 anyway.
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