Why is everyone using USB/XMOS. Why not PCIE SPDIF Out?

[cheapsoundguy]

I have been "out of the game" for a while. When I was last paying attention, around 2011-2012, the USB interfaces on most DAC were terrible.

You would literally get "crackles and pops" especially at higher res streams (e.g. 96k). Usually Coax SPDIF was the "best" way to connect with a DAC.

It seems that the USB issue is now "solved" with XMOS 208 and 216 chips. But it seems to me that USB is fundamentally a poor interface for audio, and we have had to invest a lot to work around USB's limitations.

It also seems that almost all PCs motherboards have dropped Coax SPDIF output, but almost all of them still have TOSLINK SPDIF output.

So two questions:

1) why don't more of you have PCs setup as the fundamental source using PCIE SPDIF output rather than USB?
2) why did mono makers select TOSLINK over Coax for their remaining SPDIF interface? (I recall TOSLINK is almost always more jitter/less bandwidth)?

 

[earlevel]

I have been "out of the game" for a while. When I was last paying attention, around 2011-2012, the USB interfaces on most DAC were terrible.

You would literally get "crackles and pops" especially at higher res streams (e.g. 96k). Usually Coax SPDIF was the "best" way to connect with a DAC.

It seems that the USB issue is now "solved" with XMOS 208 and 216 chips. But it seems to me that USB is fundamentally a poor interface for audio, and we have had to invest a lot to work around USB's limitations.

It also seems that almost all PCs motherboards have dropped Coax SPDIF output, but almost all of them still have TOSLINK SPDIF output.

So two questions:

1) why don't more of you have PCs setup as the fundamental source using PCIE SPDIF output rather than USB?
2) why did mono makers select TOSLINK over Coax for their remaining SPDIF interface? (I recall TOSLINK is almost always more jitter/less bandwidth)?

A few thoughts...

First, laptops dominate the market. That's pretty much the end of story right there—the market is going to focus on USB.

As far as USB being "fundamentally poor interface for audio", that hasn't been true for a long time. Recognize that it's the most widely used interface for professional (and semi-pro) grade multichannel digital audio for recording studio applications. (RME claims to handle up to 70 channels in each direction, at 44.1/48.)

I use USB for my Topping DX7 Pro, never had an issue.

 

[Killingbeans]

1) why don't more of you have PCs setup as the fundamental source using PCIE SPDIF output rather than USB?

Because USB is super convenient and omnipresent. Don't know... I use TOSLINK myself.

2) why did mono makers select TOSLINK over Coax for their remaining SPDIF interface? (I recall TOSLINK is almost always more jitter/less bandwidth)?

Mobo makers? Well, it gives zero problems with ground loops, and modern DACs have no problem squelching the extra jitter. Besides, what do we need all of that bandwith for?

 

[cheapsoundguy]

A few thoughts...

First, laptops dominate the market. That's pretty much the end of story right there—the market is going to focus on USB.

So right you are. I still have a heavy gaming PC, so I am a bit out of the norm. I forget that sometimes.

 

[voodooless]

This thing has what you ask for: https://www.terratec.de/details.php?artnr=12001&lang=en

Most argument have already been made: most interfaces are external nowadays, so very little people still need an internal card. It was standard for the last several decades though. And it was just as much driver hell as the early USB implementations.

 

[NiagaraPete]

I use usb, coaxial, and optical.

Usb = iPad / Laptop
Coaxial = DLNA from server
Optical = Airplay 2 iPhones etc

 

[Lambda]

why don't more of you have PCs setup as the fundamental source using PCIE SPDIF output rather than USB?

We have. for the professional market. "thunderbolt" is PCI-E over a USB-C connector

Thomann Thunderbolt Audio Interfaces

Thunderbolt Audio Interfaces at Europe's largest retailer of musical instruments - fast delivery, 30-Day Money-Back Guarantee and 3-year Thomann warranty

www.thomann.de

why did mono makers select TOSLINK over Coax for their remaining SPDIF interface? (I recall TOSLINK is almost always more jitter/less bandwidth)?

Jitter is no problem. Ground loops and EMI is a problem

For consumer the standard way to connect a dac to a pc is HDMI or DP.

The question is why dont we use more Ethernet / AVB?

 

[bluefuzz]

It seems that the USB issue is now "solved" with XMOS 208 and 216 chips. But it seems to me that USB is fundamentally a poor interface for audio, and we have had to invest a lot to work around USB's limitations.

It's to do with the USB Audio Class - not to be confused with the USB Standard version number (eg. USB3 or USB4). Since USB Audio Class 2 devices have become common (a bit over a decade ago) USB audio has essentially been a solved problem.

 

[Trell]

As far as USB being "fundamentally poor interface for audio", that hasn't been true for a long time. Recognize that it's the most widely used interface for professional (and semi-pro) grade multichannel digital audio for recording studio applications. (RME claims to handle up to 70 channels in each direction, at 44.1/48.)

RME uses USB 2.0 for this high number of channels and that is the reason RME has so few USB 3 or Thunderbolt interface: Not needed and adds to the cost.

RME USB - Transport audio with lowest latency and industry leading stability - RME Audio Interfaces | Format Converters | Preamps | Network Audio & MADI Solutions

RME Audio Professional Live, Studio, Recording and Broadcast Solutions. Unrivalled Quality, Performance & Stability MADI Interfaces, Converters & Preamps.

www.rme-audio.de

 

[abdo123]

Convinience, a small company like Topping would have to make discreet circuits to implement PCI-E or something else. With USB you just slap an XMOS chip on it.

 

[somebodyelse]

The question is why dont we use more Ethernet / AVB?

Competing standards, and networking requirements that most people will find too complicated or confusing. Doubly so for AVB given its networking hardware requirements, and the prices of compatible switches.

 

[somebodyelse]

Keep in mind some of the PCI-E cards are actually bridging PCI-E to USB on the board, and using a USB audio device. See the EVGA cards reviewed here for an example.

 

[Bernd]

2 more reasons for USB

1. Bandwith : it can handle everything: PCM everything up to 32bit/768 khz; DSD up to 1024 I believe. I believe Toslink is limited to PCM 24bit/192khz and SP/DIG RCA 75 Ohm 32bit/384Khz (don't nail me down on that - could be slighty different; and DSD I do not know anyway - they were specified before SACD/DSD were brought to market)

2. Asynchronous file transfer protocol: the DAC does not have to synchonize it's time signal with that of the streamer. In SP/DIF & Toslink the DAC has to work quite hard to sync with the clock of the streamer. If the SPDIF/Toslink interface is not well implemented than jitter will occur because even the best DACS cannot correct for that.

SPDIF/Toslink are really legacy interfaces and are kept rather for backwards compatibility than for superior quality ( and because well implemented they are also good enough for most users)

 

[fastfreddy666]

S/PDIF (Coax and TOSLINK) has no defined data rate. Instead, the data is sent using biphase mark code, which has either one or two transitions for every bit, allowing the original word clock to be extracted from the signal itself.

The main advantage of TOSLINK optical fiber cables is that they are immune to ground loops and RF interference and that's why they can come in handy. 24/192 (stereo) has been supported by both SPDIF Coax and Toslink for quite some time now but it depends on the capabilities of the DAC (duh). Most modern DAC chip brands (Sabre ESS, AKM and Cyrus) have some form of Jitter reduction. I don't know if the Realtek chips on PC motherboards use it but you should avoid using those things anyway. The insides of a computer are full of RF noises and can seriously degrade the audio quality. Just buy a decent audio interface (with balanced inputs and outputs) if you want good sound or make some music. and buy a pair of active monitors while you're at it. Jitter is not a problem anymore. It certainly isn't audible. This was a thing with early CD players. But just to make sure use a good quality cable and keep the length as short as possible. This is always good advice.

I had some ground loops with my TV and receiver when I used the Enhanced Audio Return Channel (eARC) HDMI port. My Kef subwoofer started to hum loudly so i could clearly hear it above the background noise (40 db+ the perks of living in a city). I think it's due to cable TV. When I disconnected the TV cable the ground loops were gone. So instead of using the eARC I use a TOSLINK cable from my TV to my Receiver. I mostly use streaming services out of convenience and the bitrate is not even 1mbps for audio. Bandwidth cost money! That's why they're still trying to reduce the bitrate of audio and video with new more sophisticated codecs. The successor of video codec H,265 (HEVC) is called H.266 (Versatile Video Codec aka VVC) and is already being developed.

 

[bravomail]

everyone has its own story. I had a good and cheap motherboard with optical SPDIF and Firewire. From 2012. Time goes, new CPUs keep coming. So when I upgraded during the lockdowns, mobo prices skyrocketed and I got barebones AMD X570 mobo without optical SPDIF. It still has somewhere inside coax SPDIF, but u need to open a case and pass the wire etc. Wtih old PC I had EMI issues over USB audio. With new PC - I have no EMI or ground loops with USB audio. So I don't use my coax. Laptop argument is very valid for USB.

 

[somebodyelse]

Depending on which physical interface spec they're following, coax SPDIF may be transformer isolated to break ground loops too. The transformer is more likely to be on the output, but sometimes on the input too. You can look for a pulse transformer close to the socket as in the HifiBerry Digi2 Pro, but not in the Digi+ Standard. Alternatively check for continuity between the outside of the RCA connector and the device ground. Motherboard audio could really benefit from this, but I've yet to see one use a transformer. This could be because the connector was sometimes jumper switchable between SPDIF and composite video, or just because they want to save a few pennies.

 

[Killingbeans]

I believe Toslink is limited to PCM 24bit/192khz

Lol, "limited"

32bit/768 KHz... 192dB SNR and 384KHz frequency extension. Fell free to call me a cynic, but people who think they can hear anything remotely in that range are nuts, IMO.

EDIT: Corrected a brainfart.

 

[Deleted member 23982]

im pretty much with you, usb has too much flaws for audio tho it still seems the best compared to "jittery" toslink, spdif seems to be a good alternative aslong no noise/groundloop is present (tho i didnt compared, actually never used toslink/spdif so far...)

i clearly hear a improvement with my moode setup, even if its still USB (modded topping D10 which just leads me to the conclusion that noise of a "normal" pc has too much influence on the sound, even if its not measureable.... and the "minimal" setup with a rpi4 improves that, also the IFI Isilencer+ helped a little but still...
i also should say i have a usb split cable to power the topping D10 thorugh a powerbank, tho the problem remains, it sounds worse on a windows pc and the only leads connected are the two data lines.... its not just 0 and 1 unfortunaly

i was just thinking yesterday... if i get a hifiberry digi+ i/o for my moode setup if jittery is a no-existant issue if i connect with toslink to the moode rpi4 and it gets processed by the processor to usb (so maybe i can avoid the noisy normal pc altogether, but still get sound for movies/games in realtime) instead of getting way overpriced "audiophile usb cards" or even rebuild a complete "music-pc"... (im pretty sure both would help tho) but the toslink route is probably the most costeffective way todo it, specially if the "reprocessing" by the rpi4 cpu maybe helps getting rid of toslink jitter again

 

[storing]

usb has too much flaws for audio

Come on, how can you say that in a world which has so many USB audio devices which work completely fine for so many usecases? Not saying it's perfect (what is though?) but 'too much flaws' is simply proven wrong by reality.

i clearly hear a improvement with my moode setup ... which just leads me to the conclusion

There are alternative conclusions which cannot simply be ruled out without hard data. One being: you just thinking there's an improvement while there is in fact none.

its not just 0 and 1 unfortunaly

It is, it's literally the definition of digital. Which doesn't mean a 0 cannot accidentally get treated as a 1 or vice versa due to some interference, but that would normally be measurable. Do you happen to have a microphone or ADC for trying loopback tests for instance?

 

[Deleted member 23982]

It is, it's literally the definition of digital. Which doesn't mean a 0 cannot accidentally get treated as a 1 or vice versa due to some interference, but that would normally be measurable. Do you happen to have a microphone or ADC for trying loopback tests for instance?

well, i just have a untrained guess and that is interference have an effect on the usb circuitry (maybe even the whole dac circuit), it doesnt have a affect of 1`s you are right but it has some kind of influence
i clearly hear a differences with close critical listening, even between pcie usb cards and native mainboard ones for example... in fact pretty much all usb sources (mainboard pc, pcie cards pc, laptop, usb hubs) color the sound somehow (specially with power/gnd connected but not only) all a bit different and like i said, the ifi silencer+ helps to some degree with that (tho moode + rpi4 still sounds superior, and i just can explain that with lower noise/jitter floor)

in fact i wish it would be easly measureable, which seems to be not the case, that would make things way easier

There are alternative conclusions which cannot simply be ruled out without hard data. One being: you just thinking there's an improvement while there is in fact none.

i did too much testing with very reproducable results/conclusions for this, and this tells me its not just my mind playing tricks else i would just hear it "different" each time but not each time exactly the same kind of "different", sorry but its ok if you dont believe me

Edit: tho i should say its not completely "crap" usb works good (i guess) but if you have setup where most "weak-links" are already ruled out you begin to hear the differences of the usb sources, atleast it was exactly this that happened to me, and at this point it was just mind-boggling so i started/kept testing.... i remember while tinkering with usb cables/usb sources and the ifi isilencer+ that the main difference was what i think is what people mean if they say "it sounds more analog"