Battle of S/PDIF vs USB: which is better?

[svart-hvitt]

I have a USB to I2S interface (I think). Is there a cheap DAC with both in them to test against?

Well, you do have this beauty:

http://en.cayin.cn/products_info?itemid=109

It depends on what you define as «cheap»...

And it’s all digital so no analog complexity added.

 

[Fitzcaraldo215]

I think there are only 3 key questions regarding data transmission protocols: bit perfect transmission, jitter and noise.

Bit perfect transmission is a complete non-issue, except some protocols may support higher sampling rates than others, but they are all adequate for most folks. There is also the question for some, like me, of support for Mch formats without multiple runs of the interconnection protocol. Except for those issues, which are possibly significant for some, none has a general advantage here.

With jitter, Amir has supplied pretty good measured evidence that at least some, though not all, implementations of each protocol would seem to offer audibly insignificant amounts, though possibly not with HDMI transmission, due to its control by the video clock. However, I do not think he has yet measured anything via I2S. Has anyone? But, still, it may be technically harder and/or more costly for a maker to reduce or eliminate jitter with some protocols than with others. Offhand, though, I don't recall seeing any measurements of asynch USB that seemed to suffer excessive audible levels of jitter, but possibly some implementations of it screw that up. And, with I2S, there is always the question of jitter induced by the long, external clock leads.

Noise transmission that interferes with the D-A to me seems like just a DAC issue, not a transmission protocol issue, although some insist that it must be painstakingly eliminated upstream and/or via gizmos in the transmission path. But, for some reason, there still seem to be plenty of DACs that have schiity noise rejection. Does Toslink have a significant advantage here? I doubt it vs. a properly isolated DAC, and Amir has numerous measurements of DACs metallically connected that show no significant problems. I also just love DAC makers who make and recommend their own addon de-noiser along with their DAC. It's like a reviewer guy recommending that you use an after-market, audiophile power cord with some electronics, duh. Did they forget someting in their original design?

So, what else could we possibly need? I will add a 4th key issue, which is wide availability of the connections for the protocol at both ends to the commonly used devices. Add to that relative ease and lowest cost for effective implementation. I think here is where we see some separation between different protocols. I will not score all common protocols on that, because the answers are fairly obvious. But, it should be noted that the non-standardized I2S protocol has a problem here.

So, in light of the thread topic, here I am with the best sound of my lifetime using asynch USB in hirez 7.1 Mch up to 384kPCM or DSD256 with up to 7.1 channels into a galvanically isolated DAC, but simply sourced from a noisy stock PC via simple plug in to a connector that was already there on the PC, actually multiples of it, and all with proper plug'n play drivers. Why on earth would I want to consider something else, like I2S requiring added hardware and driver software on the sending end in the PC?

Is there some other special sonic magic, better measurements, etc. about I2S that overcomes its practical limits in cable length, interconnect and plug standards, sharply reduced DAC selections, etc. What is the "pot of gold" for going to the trouble with I2S vs. plain old, highly performant asynch USB into a wide choice of different, well designed DACs at a wide range of price points?

Sorry, but, I am still seeing little but a mythology, an "anything but USB" dogma based on precious little actual evidence that I2S is in any way an improvement beyond asynch USB.

 

[amirm]

Well, you do have this beauty:

http://en.cayin.cn/products_info?itemid=109

It depends on what you define as «cheap»...

And it’s all digital so no analog complexity added.

That is nice looking. And not bad at $800 on sale.

 

[gvl]

That is nice looking. And not bad at $800 on sale.

One problem it is not a DAC.

 

[k9gardner]

Hi, I've just joined this forum, having dropped into this discussion from a google search on USB vs S/PDIF. A couple of questions based on what I'm reading here: First, since it's not mentioned anywhere, I guess everyone already knows about the elephant in the room - the 12k spike in all the graphs above - but I don't, so I'll ask. What the heck is that? And does this imply that all DACs know that they have to deal with this (sort of like the RIAA codecs for vinyl)?

Second, the discussion of Ethernet vs WiFi. Really? We've finally been able to get rid of the damned cables for computer networks in our homes and office thanks to WiFi, and now we're bringing them back for audio?! Ugh. I'm not sure if that's progress. In any case, I just did a little reading on this to catch up on this development I seem to have missed over the last decade and a half, but I'm still not grasping the reason why Ethernet would be preferable to traditional speaker cables in a home audio situation. Aren't we just adding two more interfaces to the equation, and isn't that generally a bad thing? Perhaps you can point me to some reading material on this.

Thanks!

 

[amirm]

Hi, I've just joined this forum, having dropped into this discussion from a google search on USB vs S/PDIF. A couple of questions based on what I'm reading here: First, since it's not mentioned anywhere, I guess everyone already knows about the elephant in the room - the 12k spike in all the graphs above - but I don't, so I'll ask. What the heck is that? And does this imply that all DACs know that they have to deal with this (sort of like the RIAA codecs for vinyl)?

The 12 Khz tone is what should be there. That is in the original file being played. Everything else is distortion and noise created by the DAC.

See this article on "J-test": https://www.audiosciencereview.com/forum/index.php?threads/understanding-audio-measurements.2351/

 

[amirm]

Second, the discussion of Ethernet vs WiFi. Really? We've finally been able to get rid of the damned cables for computer networks in our homes and office thanks to WiFi, and now we're bringing them back for audio?! Ugh. I'm not sure if that's progress. In any case, I just did a little reading on this to catch up on this development I seem to have missed over the last decade and a half, but I'm still not grasping the reason why Ethernet would be preferable to traditional speaker cables in a home audio situation. Aren't we just adding two more interfaces to the equation, and isn't that generally a bad thing? Perhaps you can point me to some reading material on this.

There is no superiority to Ethernet other than being more reliable. If Wifi works well enough where there is no dropouts, you can feel free to use it.

 

[watchnerd]

Second, the discussion of Ethernet vs WiFi. Really? We've finally been able to get rid of the damned cables for computer networks in our homes and office thanks to WiFi, and now we're bringing them back for audio?! Ugh. I'm not sure if that's progress.

Well, I don't.

My Roon server runs on an iMac in my home office / DAW mixing set up.

My Devialet is in my living room.

I stream from Roon to the Devialet over wifi.*

*Well, technically, there is another wifi access point in the living room that connects from the AP to the Devialet over ethernet, but all of the intervening connections are over wifi. The only reason I bother with the short 2' ethernet cable is that the Devialet phono stage is quieter with the wifi card disabled.

 

[jakevoss96]

In my recent experience, I guess it really comes down to what works for you. Since USB is the winner here I would prefer to use it but since my PC delivers an audible electrical hum through both 3.5mm and USB my only option is to use optical which delivers to me an absolute clear channel (to my ears) devoid of any audible interference.

 

[Sal1950]

In my recent experience, I guess it really comes down to what works for you. Since USB is the winner here I would prefer to use it but since my PC delivers an audible electrical hum through both 3.5mm and USB my only option is to use SPDIF which delivers to me an absolute clear channel (to my ears) devoid of any audible interference.

I take it you mean using the Toslink optical removes the hum = ground loop hum.
I struggled with one myself, no reason not to use optical, it will sound as good as any other. Only possible negative is you may have trouble with 192 sample rate files, maybe not?

 

[jakevoss96]

I take it you mean using the Toslink optical removes the hum = ground loop hum.
I struggled with one myself, no reason not to use optical, it will sound as good as any other. Only possible negative is you may have trouble with 192 sample rate files, maybe not?

Depends on whats pushing the optical output. My AE-5 can only do 96Khz over optical but the new AE-9 can push 192Khz over optical according to their specifications page.

 

[Sal1950]

Depends on whats pushing the optical output. My AE-5 can only do 96Khz over optical but the new AE-9 can push 192Khz over optical according to their specifications page.

Spec's can sometimes only tell you so much for sure. I can do 192 over Toslink from my computer to my Emotiva DC-1 if I keep the cable down to about 1 meter. Much longer and it won't lock on? I don't have any 192 stereo files to stress over in any case, I keep one on the drive simply for various testing purposes.

 

[Rockfella]

Sal1950, did you accomplish this by installing a sound card with Toslink in the computer, then connecting the computer to the DAC via Toslink?

I might have to do this if I face issues connecting my K5 Pro to my PC through USB.

 

[Sal1950]

I might have to do this if I face issues connecting my K5 Pro to my PC through USB.

Ground floating cheater plugs can be your friend.
(NO, I did not recommend this. )

 

[RCAguy]

Very interesting analysis, Amirm. Notice the 60 & 120hz hum in the USB v. none visible in the SPDIF. Is this because optical SPDIF can nave none of USB's metal ground loop? With 18in subwoofers flat to 31Hz and capable of monitoring subway rumble in recordings, during quiet passages hum can be objectionable.

 

[watchnerd]

TOSLINK FTW because lazers are cool.

 

[Mark Lawless]

I've always struggled with a ground loop hum when using USB or S/PDIF over coax between my tower and DC-1.
I could solve it by doing some things I'm not totally comfortable with, like floating all the power grounds, etc.
Toslink neatly solves it without any negatives I can see here.

I have recently discovered that Optical with my Topping D30 is nowhere near as good as my USB sound quality that is, connected to laptop. I had some issues with usb but it was a connection problem. I believe the optical has problems with jitter issues. But whatever the USB sounds amazing.

 

[Sal1950]

I have recently discovered that Optical with my Topping D30 is nowhere near as good as my USB sound quality that is, connected to laptop. I had some issues with usb but it was a connection problem. I believe the optical has problems with jitter issues. But whatever the USB sounds amazing.

That shouldn't be, though Amir found some issues with the D30's handling of S/PDIF data. I'm not sure I believe the issues to be audible but short of a DBT of the two impossible to say for sure.

 

[DonH56]

TOSLINK FTW because lazers are cool.

"Laser" (light amplification by stimulated emission of radiation) but actually it's a red LED in a TOSLINK connector...

 

[watchnerd]

"Laser" (light amplification by stimulated emission of radiation) but actually it's a red LED in a TOSLINK connector...

Satire my friend.....hence the "Z".....

(Full disclosure: degree in Applied Physics, worked on signal processing for x-ray laser research projects in upper division lab work)