SPDIF out of the PC is the worst way to connect up digital audio?

Continuing the discussion from Effect of Roon Core PC hardware configuration on sound quality:

@Carl - I took the liberty of trimming out most of your comment from the originating thread. This is really a spinoff topic on your last statement about S/PDIF. I was shocked to see it - given that all the best DACs in the world seem to use S/PDIF, and you would not think they would do that if it was a way to totally ruin the benefits of the uber-expensive clocks they use. That said, a bit of research on-line quickly led me to understand that MANY people feel S/PDIF is horrible, and likely to lead to jitter. So…

What is the best way to connect ANY Roon to a quality DAC? I can’t accept USB as an answer IF we are talking about putting a PC (or Mac) anywhere near my hifi. And long runs of USB cable are likewise problematic. That could leave balanced AES, but as I understand it, it’s subject to the same problems as S/PDIF. Plus few DACs support that for input. So then what?

Granted, when RAAT and RoonSpeakers are available and implemented, there may be some better answers. But for now, what way would you recommend?


PS - Anyone else that can speak well to this question, please chime in.

PPS - Tone is tough to master in the written word. So if this seems like a confrontational question, please note that it’s not meant that way. The statement surprised me. I found others that seemed to agree. And am now genuinely curious about where that leaves us, though also am not yet convinced the original statement is always correct.

I believe the general issue is typically with the PC’s clock, not with the S/PDIF interface itself. Look at something like the Wyred4Sound Remedy Reclocker to reclock the optical output of your PC (or any problematic source with an S/PDIF output (Toslink or Coax), e.g. Airport Express, CD transport, etc.).

As far as the “best way”, that is highly dependent upon the streamer, downstream DAC and your ears. USB has gotten very good recently, including support for higher resolutions (e.g. 384KHz / DSD). S/PDIF optical (Toslink) provides galvanic isolation, but I’m not well versed enough to compare / contrast S/PDIF coax and AES with Toslink.

Whilst I respect your distaste for having a computer close to hifi equipment (backed up by Roon staff members posts on this forum), a Mac Mini directly connected by FireWire to a high end DAC has provided me with 4 years of sonic bliss. I look forward to experimenting with a future RoonReady streamer and letting my ear be the judge. Other advantages of a local computer (also connected to a good TV) are the ability to view YouTube music videos and concerts and play movie files saved to the computer.

Getting back to your original question, at the moment, there there are no ways to get great results without a computer connected to a DAC, with the exception of some Meridian gear. Using SPDIF out of a computer with specialist sound cards is all but forgotten now. The advent of asynchronous USB audio revolutionised the world of us computer audiophiles. Some companies like Berkley Audio have seperate boxes for USB>SPDIF and DAC with SPDIF input with great results. It all depends on the implementation. Expensive quality DACs usually support multiple inputs to give a user flexibility in connecting legacy kit.

Looking to the future, products like the Auralic Aries currently has:
Input: Ethernet, Wi-Fi
Output: USB, Coax S/PDIF, Toslink, AES/EBU
I assume it could become RoonReady by a firmware upgrade. I would choose the USB, but would try all interfaces that my DAC supported.

Before I even begin my reply, I’d like to start with a disclaimer… I’ve got no experience with anything connecting to a DAC but asynch USB and various S/PDIF connections. And clocks? I’m still trying to wrap my head around the MULTIPLE clocks in this musical reproduction process. Thus my OP.

Thanks mrvco. And now that I’ve done a bit more digging, I see that it’s not as simple as saying “the PC’s clock” - as I am understanding it. There are, depending on the subject in question, multiple clocks. As far as S/PDIF is concerned, there appear to only be one - the clock that governs sampling rates. And the source owns that clock. Which is supposed to be a bad thing, but has me scratching my head.

That’s because a cursory review of truly high end (that’s spelled $$$) CD transports show that many of them use S/PDIF connections to a DAC. Common sense says that S/PDIF must be able to be used without jitter, or the various vendors of crazy expensive DACs would not expose themselves to criticisms around poor performance. So S/PDIF must nor always be bad. Or so it would seem.

Jeff - I respect your respect. Thank you. It’s good to be able to disagree in this way. HOWEVER, at the end of the day, people with aversions to PCs (Macs) in near proximity to their Roon device either need to be satisifed that there is no need for concern, or that there is a workaround (which I’m looking to RAAT/RoonSpeakers for). So IMO it’s not off topic. Though - naturally - we do not want to decend into the rabbit hole of disagreement. Clearly we are in a space where people’s mileage are going to vary.

First, as far as I understand it, anything providing digital input to a DAC is a computer, CD transports included. It’s just that some are “traditional, personal” computers, and some are specifically tailored for audio. Meridian and many other vendor products fall into that category. There are currently many music serving computers (one of the cheapest being Aurelic Aries) that the industry is falling over themselves about that apparently serve up spectacularly good signals to DACs, and can do it over S/PDIF.

Therein lies my confusion over S/PDIF as poor source.

And it’s made a difference for me. It’s what I use. But even asynch USB as a medium for music transport is not without it’s challenges (which I why I have a Schiit Wyrd). So I’m hard pressed to see it as ideal. Though - as I understand it - its one GREAT strength is that it turns all sampling rate clocking (not media transfer rate clocking) over to the destination.

As before, where I’m off base, please set me straight. Thanks!

Hi Jeff,

I believe that work is underway as we speak to make the Aries RoonReady.

As a personal aside and at the risk of derailing @scolley’s thread, my little audio world would be complete (for now !) if the Aries could also be an HQPlayer NAA. That would enable HQP to stream to the Aries after Roon sends output to HQP.

I emailed Mr. Wang about it and he indicated it may be a possibility in the future but Auralic is a small company and has other things to develop. Accordingly I am encouraging anyone with an interest in the Aries and HQP to contact Auralic and let them know the extent of this emerging HiFi crisis !

Danny suggested that greater integration with HQP so that content could be returned by HQP to Roon and then streamed via RAAT would be the best outcome, and I agree with that. I posted to Jussi in CA about that and he noted that it could involve a reduction in SQ. I think that means no (or at least not at this stage) because I can’t remember anything that Jussi has done with his product that would involve a reduction in SQ …

/derail over

I believe high end manufacturers still sell CD Transports because some folks want to buy them, not because they deliver the best sound from a “Redbook” 16 bit / 44.1 kHz digital audio file. The high end manufacturer Linn discontinued CD transports years ago because they were inferior, expensive, old fashioned, mechanical technology. My system has no transport for sound quality and user interface reasons. The downside is that the user has to be a computer geek.

Yes, the Aries has a SPDIF coax output as well as USB and Toslink

@andybob Which Aries output do you use to your DAC and why?

I currently use the AES/EBU because the USB input in my DAC (Vega) is needed for Roon. If I had my d’ruthers the Aries would be able to switch from RoonReady to NAA and I would then use the USB from Aries to DAC to enable streaming DSD.

A friend of mine swears by the AES/EBU connection (which I understand is still SPDIF) saying that it provides a rock solid connection for the VEGA Exact Clock setting and that DSD is basically just a way of listening to demo tracks, not the music you want to listen to. He also thought it was a slightly “darker” sound, more forward in the mid-bass, and that he found USB a bit lacking in that regard. Streaming Tidal or Redbook after upsampling to DSD in HQ Player would mean the second reason was irrelevant.

Edit: I use USB in for Roon, which is 99% of my listening. I think it sounds “airier” and I can listen to demo tracks in DSD whenever I want. I have an UpTone Regen which made a small but significant improvement. I use a 5m Belkin cable which I plan to replace by shifting things around.

Thanks @andybob , this is an interesting tread!
Chris Connaker from Computeraudiophile site reviewed the Berkeley Audio Design’s Alpha USB interface. Berkeley go to great lengths to put an extremely accurate clock in the US$1,895 Alpha USB. The secret is great engineering and implementation on a product by product basis.
I have paid a lot of money for a DAC with a good clock and am loathe to buy more kit, but concede the Berkley approach of getting good clock timing in the USB or ethernet interface box as well as good isolation from the computer gear looks very sound.


All my research suggests that SPDIF is one directional and if used, the clock of the upstream source is used , not the DAC clock.

A note from an IT infrastructure guy: the relevant clock is not necessarily where you think it is. It is a simple matter, no matter which interface type is used, to simply land the data (audio stream) and then feed it to the DAC using an internal clock. So long as the external interface is faster than the internal need for data, no problems will ensue. All the interfaces being discussed can easily transfer data at a far high rate than required by any DAC hardware. All modern DAC implementations that I know of have an input buffer for just such a reason.

In terms of sound quality, electrical noise (digital or analogue) and the quality of the analogue stage will have a far higher impact on sound quality than the input port used to transfer the data. Don’t worry over the data transfer method and just trust your ears, they are the best tool for analyzing the sonic quality of a DAC.

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A good USB or S/PDIF implementation is a good implementation. S/PDIF has served the audiophile community well for many years and is very mature. USB has some advantages, but it is a general purpose interface that has been embraced by the audiophile community and continues to be optimized for audio applications.

The main reason that putting a PC or Mac in your listening room isn’t considered ideal is due to fan noise, mechanical drive noise and potential RF / EMI interference (things that should never be an issue with a quality CD player or transport). I do have a Mac Mini attached to my DAC and recently swapped the HDD with an SSD due to the periodic clicking of the HDD. Converting the Mac MIni to fanless is the next step, but hopefully the Sonore μRendu becomes available before I get that itch.

I also have an Oppo Blu-ray player that I use as a transport (Oppo–>Remedy Reclocker–>DAC). However it has become rare that I stick a CD in it when my entire library is at the ready in Roon and any sound quality differences are negligible at best.

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Lot’s of great dialogue here. Thanks folks!

In my web wanderings to get more info on this question, I found a couple of videos that seem to provide a great deal of clarity on this topic. Worth a look if you have a few minutes.

A video intro to DAC interfaces


More detail on DAC interfaces, specifically problems with the connections.

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@scolley thanks for the links to the excellent YouTube videos by Hans Beekhuyzen. I also purchased his eBook “File Based Audio” but have not read it yet.

Thanks for the feedback Jeff. I thought the videos were pretty good also. VERY good actually, IMO.

However, I would not have known about them had another Roon community user not turned me on to Hans Beekhuyzen a few weeks ago. So here’s my shout out to @gmt for pointing out that excellent resource. Thanks pal!

A pleasure - this was linked on the amazing Meridian Unplugged forum (which also has a Roon section)

Meridian - Streaming Hardware with Roon Application


Wow… let’s looks exactly like what I’ve been dreaming of for my 2-channel system.

Thanks for the heads-up… I’ve subscribed to their e-mail list.

So glad I read this thread.

When I hooked up my DAC by USB for the first time I could hear quite a lot of popping/cracking. Instead of trying to fix that I swapped to my optical input which sounded great I thought and had no popping sounds.

Also, the USB input is a max of 24/96 and the optical SPDIF is 24/192, so I though, great I will leave it like that.

After reading this thread, I tried the USB again and managed to sort the popping sound by isolating the DAC to its own USB controller. Now it is working, I notice a significant improvement in the sound. I don’t know why, just that it is better. A lot better. The vocal seems clearer and the sounds ‘tighter’.


When I had a Hugo, I tried the toslink, high rate USB, and standard USB with an Olimex galvanic isolator - which at that time was the fastest version available, limiting playback to redbook.

As much as I thought I could hear differences between toslink and high speed USB, I could never settle on a preferred, which looking back I conclude they were the same and I simply ‘wanted’ to hear something. In fact I learned the hard way about this in general - I think we are fooled by our hearing system far more than we think and wrongly assume our ears are a calibrated, consistent and reliable tool for comparative listening which is no way influenced by our subconscious brains or even how our body is feeling in general on any given day.

From memory Rob watts felt toslink was better on the Hugo and that was his primary input for development, bettered only by the Olimex solution.

I hated the Olimex solution. Who knows why - maybe it was the additional USB cable in the chain - but it sounded horrible. I ended up mainly using the standard high speed USB input from my Mac mini, predominantly because it just seemed simpler as it supported everything.

I’ve read loads about toslink jitter, but then again I’m sure it depends on how much money was spent on each input on a device and how mature each system is. USB was after all invented to connect printers or whatever, and has somehow been upgraded and managed to make work better for Audio simply because it’s become an incredibly common and standard connection and that is often what wins over ‘better’ solutions.

I know there are technical pros and cons for all, but I wonder in the real world how much effect the input has on well designed kit, compared to other factors like your mood on any given day, fluctuations in power, noise generated by other appliances in the house, atmospherics, temperature, background noise changes, etc etc.

It’s good we always strive for the best, and I’m sure I’ll keep fiddling with my setup, but I’m a lot more ‘over it’ in all that experimentation now. Room correction had miles more impact than any other tweak I ever wasted time worrying about, so I’ve learnt to just plug in a few times and see what makes me happy and is also convenient, and then move on to other things. But then I don’t have an Uber hifi (it’s the best I’ve had but nowhere some peoples systems), so maybe these things aren’t as obvious.

I thought you guys might be interested in this thread setting out some of the differences between the different protocols (including RAAT) and clock ownership.