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When should you use a USB to S/PDIF converter?

  • This week I added USB-S/PDIF converters and S/PDIF re-clockers to the Darko DAC Index. I’ve had direct experience with a number of these now and it’ll come as no surprise that some are better than others. Some are more expensive than others too so my star rating attempts to capture that old standard: bang-for-buck.

    I’ve rambled about the importance of these units before. Essentially, the stock USB in many budget DACs won’t give you as good a sound as a high-quality S/PDIF feed from one of said external USB converters or re-clockers. Think of it as outsourcing your USB management for better sonic results.

    Experience tells me that most budget DACs benefit from an Audiophilleo or Resonessence Labs Concero or Wyred4Sound uLINK acting as a go-between betwixt computer and DAC. The technical whys and wherefores are for engineers to explain but I essentially it’s down to a combination of re-clocking – that erodes phase-error inducing jitter – and (some degree of) isolation from the host computer’s noisy USB power supply.  In short: re-clocking and power supply.  Clocks and power.


    My first taste of an Audiophilleo being surplus to requirements came when reviewing PS Audio’s PerfectWave MKII DAC. Paul McGowan’s Digital Lens “NativeX” tech now buffers/re-clocks EVERY input on the second version of the PerfectWave. Essentially it can correct timing errors within the USB data stream.  From a reviewer’s perspective, this is NOT a good DAC with which to test the quality of a USB converter.

    It’s not uncommon these days to see more thought put into USB implementations further up the DAC food chain. For its USB input, the Metrum Hex feeds an OEM Hiface module via an internal power supply; it sounds wonderful. Ditto AURALiC’s Vega; which also powers its large USB buffer internally. For these DACs, I’ve found a USB converter unnecessary – they sound tremendous in their own right.  Good!  After all, when you’re spending $3k+ on a DAC you’d probably expect not to need to deploy the Concero or the uLINK to optimise the fidelity of your new toy.  Both Metrum Acoustics and AURALiC have done excellent things with clocks and power.

    Moreover, your USB-S/PDIF converter should never make your DAC sound worse!  If it does, something is very wrong.


    Again, from a reviewer’s perspective, neither the AURAliC nor the Metrum are DACs that would reveal differences in off-board USB converters.  At the other extreme, the original Metrum Octave Mini offered no USB input whatsoever but its S/PDIF input was extremely sensitive to upstream converters/re-clockers.

    In the sub-$2k market stock USB is more inconsistent in its implementation quality. Things are improving though. The widely-deployed XMOS chip has brought an overall lift to the budget USB game and players like Schiit and CEntrance pay particular attention to their implementations, whether it be by eschewing the stock XMOS firmware code and writing their own and/or paying closer attention to the USB input’s power supply quality or galvanic isolation or whatever. I’ve heard great things about Kingwa’s newer USB32 module over at Audio-gd. It’s something that I’ll be investigating personally as time permits.

    So – how do you know if your DAC will benefit from a USB-S/PDIF converter or not?  First up: ‘asynchronous USB’ gets touted by marketing departments as a fix-all solution.  It isn’t.  I’ve heard numerous DACs that use an async USB implementation but slap an Audiophilleo or Concero on them and presto (!), an altogether more vivid and propulsive presentation.  We need to dig deeper into what the manufacturer has done with USB to find clues as to how good it might sound.  An XMOS chipset is no magic bullet either.  Ditto galvanic isolation.  They all help, yes, but they still might not surpass the tonal colour and bass energy that you hear from many an off-board box.


    I’ve said it before: if 2011/12 was the year where the digital audiophile in the street woke up to fixing jitter with better data clocking, 2013/14 will be the year he wakes up to the quality of USB power.  Look for manufacturers that not only make a big noise about their USB being asynchronous but also where the power is sourced from within the DAC itself (and NOT your noisy PC) or a power supply that’s heavily regulated/filtered.  Of course, you can take power supply matters into your own hands with iFi’s excellent iUSBPower unit or by slipstreaming some battery juice via Elijah Audio’s BPM module and ISOLAATE cable solution.  Want re-clocker and battery power all in one box?  John Kenny has you covered with his Ciunas converter.

    I’d like to open this discussion to the floor.  I’m keen to hear from readers in the comments section below: Which USB converters make a difference to which DACs?

    John H. Darko

    Written by John H. Darko

    John currently lives in Berlin where creates videos and podcasts and pens written pieces for Darko.Audio. He has also contributed to 6moons, TONEAudio, AudioStream and Stereophile.

    Darko.Audio is a member of EISA.

    Follow John on YouTube or Instagram


    1. Hi John,

      I can attest that the Ciunas DAC alone does a much better job than the iUSB > MF V-Link192 > EE Minimax combo.

      The iFi iUSB did a great job lowering the noise floor but the sound still had a certain sterility to it.

      The Ciunas DAC completely does away with that and I would imagine the converter would be just as competent when used with an equally competent DAC.

      Reclocking the signal at the chip’s input, thus reducing jitter, is probably the main reason for its non-agressive sound. Its minimalist design does what some much more complex topologies can’t seem to nail.

      I’d be curious to see what a better spec’d chip could achieve in a similar design. Mind you I’m no expert at interpreting a chip’s technical data but the 5102 does appear to have inferior dynamic range when compared to other chips being widely used(namely ESS)How would this translate? I don’t know…I’m basically just rambling on at this point.
      I trust Kenny has good reasons, other than cost, for choosing the 5102…or not.

      • It doesn’t surprise me that you prefer the Ciunas to the MF + EE. Even the JKDAC32 was a superb unit.

        • I find it interesting to see how DACs like the Minimax, certain Audio GD offerings and a few others are beginning to lose feathers as the bar is being raised by newcomers. Everything is relative.

          I’ve never had the chance to listen to the Auralic or Hex “dream machines” but I’d like to see to what degree the law of diminishing returns applies when compared to the Ciunas.

    2. I have used the W4S uLink and the iFi iLink and from what I am hearing, the iLink is much better. I Also have used these converters with Twisted Pear’s Buffalo Dac II. I also have used in the past M2Tech HiFace but have graduated from it and moved on. The Buffalo dac is a good performer on its own and it is taken to another level by introducing the iUSB Power and iLink into the chain.

      Hope others would also share their experience with the iLink, being one of the newcomer in the converter arena.

    3. This may sound like a ‘look what I’ve got’ comment, but I promise that isn’t the case.
      I have a danish Audio designs DAC, designed and built by Ole Nielson (you may have heard of OnTech). This is now a three-box unit, having started as one and me having been a guinea-pig for developments… The DAC, the PSU, and a large amount of capacitive smoothing for the power supply. No USB input.
      To this I have added an original Sonicweld Diverter, ‘won’ in a swap for some other kit I had. I have tried many other USB -> S/PDIF converters in the past, including the HiFace, JK HiFace, HiFace 2, Audiophilleo, Kingrex, SotM, and others. Perhaps unsurprisingly I feel the SW is the best of that bunch… With my DAC. This may not always be the case. We did once try a blind comparison, btu the differences are so stark my wife can tell from another room.
      Key in using an external converter is the power supply. The Kingrex and SotM are particularly affected by this.
      Try a few. See what works for you.

    4. The USB 32 chip should be really good. The good thing is that it is included in all newer Audio GD units regardless of price. Looking forward to your comparison to how it fares against other USB implementations.

    5. The better the DAC and USB implementation, the more the mid-level USB converters become irrelevant. That doesn’t mean that you *can’t* improve on the PWD or Hex though, just that the Audiophilleo or Stello or similar converters are no longer enough.

      The Off-Ramp 5 into the PWD II with NativeX turned off for example beats the PWD’s own asynch input with NativeX. It’s that good. The question there is whether you should spend $2K on a USB converter into a $4K DAC, or just put all the money into something like a Luxman DA-06 or Bricasti. Of course there’s no guarantee that just because you’re spending $6-7K, the native USB inputs on those DACs are any better than the PWD’s or Metrum’s. Price is still doesn’t correlate to USB input quality.

      • That’s interesting to learn about the OR5 + PWD combo – thanks. I guess that’s the conundrum with the OR5 being so much more expensive: do you splash on it or put the $2kish towards a better DAC. As you correctly assert though, more expensive DACs don’t necessarily bring better USB.

    6. Great article, I think you’ve sold me on the uLink to stick between my Mini and Peachtree Nova via coax ( it has adaptive USB and limited to 16/44.1 or 16/48, unlike the new Nova 125).

      I am curious, though, if you have had any dealings with Peachtree’s own X1 USB/SPDIF converter. I have no need for BNC or even the optical at this point, but it is $100 cheaper than the uLink, although I am not sure how it will work with Audirvana.

      Thanks and keep up the good work.

      • Alas, not heard the X1. I *do* know the uLink lifts the Nova125’s performance.

    7. My DAC is the Bel Canto 2.5, which is not top of the line by any means, but a step up from the $1,000 – $1,500 DAC’s I auditioned. Earlier this year, I had in my system, at the same time, the following usb/spdif converters: Berkeley Alpha, ART Legato II, Bel Canto REFLink, and Bel Canto uLink. All 4 converters improved the sound of my system, with the Berkeley Alpha USB coming out on top (unfortunately for my wallet). I am very happy with the Berkeley unit. One other note, with the very best usb converters, such as the Berkeley, even expensive, well-regarded DACs can be improved. For example, I have researched and reviewed every comment or review I could get my hands on, and anyone who used the Berkeley Alpha USB, with the Berkeley Alpha DAC (both the original, and version 2), reported a very noticeable improvement in sound quality. The Berkeley Alpha DAC is, in my view, very much among the best DAC’s available, particularly if you value a neutral sound. So, it is not just the lower end DACs that can be improved with a usb/spdif converter.

    8. I got this from Jason at Schiit on July 9th, 2013:

      Keeping in mind that I would most likely not need balanced / XLR connections on any other component and that our computer is a 4.5 year old Dell Inspiron 530 PC running Windows Vista Home Premium 32 bit … which is the better way to go (or the preferred-by-you way to go) for better sound ?

      Option 1.
      Buy one of your Bifrost’s with the Gen 2 USB input upgrade and the Uber Analog upgrade with an M2Tech HiFace Two USB to SPDIF converter (that plugs directly into one of the computer’s USB ports so there would not be an interconnect cable between it and the computer) and a Kimber Kable or Audioquest digital / coaxial cable out of the HiFace Two into your Bifrost’s digital / coaxial input ?

      JS: “Actually, if you get the Gen 2 USB input, you don’t need the HiFace–and our USB implementation is superior to pretty much any affordable USB-SPDIF converter out there.”


      Option 2.
      Buy one of your Gungnir’s with the Gen 2 USB input upgrade (built in I think) and use a Kimber Kable or Audioquest high quality USB cable directly from one of the computer’s USB ports without any USB to SPDIF converter ?

      JS: “Same here. Gungnir will be better than Bifrost across the board, even from the RCA outs….”

      • Jason’s sending me a Gen 2 USB-d Bifrost next month so I’ll be able to hear this for myself. 🙂

    9. I had a Audio-GD DI v1 between my MBPro and Rega DAC for a long time (over a year). And the difference between the DI and the optical out was very slight at best. So I was skeptical about USB/SPDIF converters. And $600 for the better converters is too much for my system.

      However, I came across a great deal for a MF V-Link 192, and this really did have a noticeable improvement upon the MBPro Optical and DI.

    10. Hey John,
      Introducing the vlink 192 to the uber bifrost certainly wasn’t a night and day difference, but there was better low level detail and slighty better separation of instruments. Small changes but good changes. Curious to compare to Schiits new USB implementation.

      • Thanks for adding to the pool of real-world experience, Alex. Much appreciated.

    11. I hope Jason includes the Uber analog card with the Bifrost. It is well worth your time.

      My set up includes the Ubered Bifrost sans USB. Instead I am using the Audio-GD DI-V3S & DI-PSU. The combination is a lot of fun. I don’t have experience with too many converters, but I do like the DI-V3. However, I felt the Uber made a more substantial improvement to the Bifrost sound than the DI-V3, in my system. The Uber is that good.

      • That’s good to know – and yes, I’m getting the works on the next Bifrost.

    12. I’m a big believer in external USB-to-S/PDIF converters. I use an Audiophilleo 1 with my Rega DAC and a Sonicweld Diverter HR (the original version) with my Berkeley Alpha Series 2 DAC and get wonderful sound. I don’t necessarily agree that an external power supply makes a difference but an open to reconsideration. See my column in Positive Feedback Online for more details. Thanks.

      • Thanks for stepping into the discussion, Andy. I recently got my hands on a Sonicweld Diverter but haven’t had time to play with it…yet.

        • Thanks John. I have considered getting my Audiophilleo 1 updated to use the new external power supply but (a) I’m not sure that it’s necessary as I like the sound the way it is and (b) I’m not sure I have room for another “wallwart” in my power strip under my desk in my backup system. I look forward to reading your articles on external power supplies. I know that, at last count, Josh at Sonicweld had no plans to make an external power supply available for the Diverter HR2. At least that’s what I read in a forum with a reply from Josh. I look forward to your thoughts and observations of the Diverter HR2 (which is the one I assume you have). Best regards, Andy

          • Actually, I have the original 24/96 Diverter on loan from a mate – probably won’t be reviewing it here.

            • That’s still a nice piece of equipment. That’s what I started out with. It just doesn’t do 24/88.2.

            • Yeah, there’ll be no software up-sampling going on when I finally hook it up.

          • Andy’s experiences with the SonicWeld mirror my own. For convenience, the Halide Bridge is hard to beat, but in terms of performance the Sonicweld seems to be head and shoulders above most, and is better than any other similar product I’ve tried.
            I’ve not found too many problems with the lack of 88.2 support. Maybe I’m just lucky? There’s the occasional recording I can’t replay but hey are very few and far between.

    13. Schiit uses the CM6631A in their new USB boards, not XMOS. I’ve been using an Off Ramp 3 with mid level options for several years (last generation adaptive USB) and recently compared it to a new relatively inexpensive DIYINHK async USB-S/PDIF converter based on the latest generation XMOS XS1-U8A-64-FB96. Running into a Schiit Bifrost Uber. The older Off Ramp is noticeably more full and organic than the DIYINHK, but the the latter was powered by the USB port with the converter’s internal filtering. I’m also suspicious of the quality of the S/PDIF output in the DIYINHK box which could easily play into the sound quality of the converter. Steve Nugent at Empirical Audio knows proper S/PDIF implementation and I expect I have a proper connection from the Off Ramp 3 to the Bifrost via an Audioquest VDM-5 silver digital coax cable.

      I have another relatively inexpensive async USB-S/PDIF converter in route from Hifiwow based on the same CM6631A as Schiit uses in their latest USB boards. I expect Schiit’s board would be superior for a number of obvious reasons, one of which is there’s no S/PDIF step to degrade the signal. It will still be interesting to compare it to the XMOS based converter and Off Ramp 3.

      Afterwards I’m rebuilding my music server and installing a Paul Pang Professional Audio Studio USB card and an ApeXi AXF-104 PCI/PCIe power filtering card. The USB card is entirely powered by an external 5v power source, in my case a linear regulated PSU, and everything powered by the USB connector will be sourced from it. I suggest you look on the web for information on both of those items. They are relatively inexpensive components for improving computer music servers. After the server upgrade I’ll run the comparisons again.

      I’m very much looking forward to your impressions of the Bifrost Uber. The Uber upgrade makes a very noticeable difference. Also looking forward to your impressions of the new USB input versus the converters you’ve been sampling connected to the Bifrost Uber.

    14. I had the original Sonic weld diverter – It was in a different league to the jk ciunas, jk mk3, and PurePower AP2 that I also owned. The new HR version is said to be even better.

      The only downsides of the original version are lack of 88k support, and not being able to play above 96k. These problems are addressed with the later version which now supports up to 192k.

      The only reason I sold it is due to the fact the USB input on the AMR DP777 DAC I now have is equal (but not better) than it. Other DAC’s I have tried with very good native USB input are the VEGA, MSB Analog and Lampizator.

      • Thanks gav. Yeah, the USB on the AURALiC is excellent isn’t it? Thanks also for adding MSB and Lampi as additional data points.

    15. we should just stop using USB altogether…what an inferior solution from computer to DAC….ethernet is the only way if you want proper timbre and colour of instruments and lifelike transients, and it wont include all the noise that travel along USB cables.

      • I’m not at all inclined to disagree, but I’ve not seen any simple way to get audio out of the Ethernet port, or any DACs that will accept an Ethernet input.

        USB does have limitations and drawbacks, but it is very widely supported.

    16. Hi John, I’m going to purchase one of these spdif converters to go from my pc to my rega DAC. I’m using my NAD CD player as a transport at the moment because I can’t seem to get as good SQ from the pc, using either USB or the spdif out on my computer. I’m not sure whether to just get a budget hiface 2 or something a bit more expensive like audiophilleo 2. anyone have any recommendations? i would prefer to go for the cheaper option but not unless I’ll hear a good improvement. Thanks

        • I agree. I use an AP 1 with a Rega DAC in my backup system and get fabulous results, better than the Ayre QB-9. Save your pennies for the AP 2.

    17. Relatively inexpensive combination of Weiliang “Breeze Audio” CM6631A USB-S/PDIF converter (Newest stereo C-Media USB receiver, NOT CM6631) with a DIY Paradise Ultravox ADuM4160 USB isolator for up to 24 bit 96 kHz. Users must understand the restrictions (operates as a USB 1 full speed device). Relatively inexpensive combination with amazing performance value. Much better than my Off Ramp 3.

      Schiit DAC owners with the new gen 2 USB board (CM6631A) should try an ADuM4160 USB isolator. Provides a significant improvement on stereo image bloom. Same restrictions as mentioned above.

      • Thanks NY. I’ll be getting a Uber Bifrost next month. I guess I should drop some cash on the ADuM4160 USB isolator?

        • I think you will find the result interesting. I know Jason at Schiit is aware that isolation on the USB input creates a quality advantage and they’re working on something related to it. You may want to try connecting an Audiophilleo to compare versus the gen 2 USB input alone and with the ADuM. I’m getting significantly better image bloom with the Ultravox ADuM and CM6631A converter combo on the Bifrost Uber than with the Ultravox on the CM6631A gen 2 USB board, although there is still a significant improvement over just the stock gen 2 USB alone. Please keep in mind that ADuM4160 devices are incompatible with most newer async USB receivers including the XMOS that many high end manufacturers are using. You can read about my recent experience on page 28 of the Bifrost Uber Upgrade thread at Headfi. A lot more information there. That thread is ground zero for testimony on the Uber upgrade. I expect you’ll find the Uber a very noticeable improvement over the stock DAC board. Most of us did. -Thanks for your time.

          • …and thank YOU for your excellent post. I’ll investigate the ADuM further.

            So – *definitely* doesn’t work with XMOS receiver chips?

            • I looked in tech forums for experience with the ADuM on XMOS receivers and the little I found indicated incompatibility. I tried the Ultravox ADuM on a new inexpensive USB-S/PDIF converter based on one of the latest XMOS receivers and it didn’t work.

              The ADuM was popular when adaptive USB in computer audio was popular. As I understand it, and I’m no expert to be sure, as USB technology in audio equipment evolved, audio equipment manufacturers shifted toward asynchronous USB protocol with compatibility for higher resolution music, the tech manufacturers designed USB receivers for audio and throughput solely at the USB 2.0 spec. The ADuM is USB 2.0 compatible with the host but it won’t pass a host-peripheral handshake at the USB 2.0 spec, so all the newer USB receivers that can’t operate at USB 1.0 won’t work with the ADuM. When the ADuM mostly stopped working for newer audio applications I believe most people with experience stopped thinking to try it and many people newer to computer audiophile USB have never heard of the ADuM and USB isolation. I expect many people prefer simple plug and play operation and have no interest in tweaking what they have.

              The ADuM is very limited to what it can do with today’s USB audio equipment. It apparently doesn’t work with the previous version of the C-Media receiver (CM6631) that Schiit used in the first generation USB board and nobody thought to try it with the new version. I happened to be in the right place to try it on a CM6631A device and the Schiit gen 2 board soon after. You’re in a great place to try it with the hardware you review.

              There are design advantages to the DIY Paradise Ultravox ADuM device over others. It is designed for use with audio USB where most others are likely based on the reference design for electronics projects and medical applications. The Ultravox is also more expensive including shipping cost. You’re a lot closer to the guy running DIY Paradise (Malaysia) and your shipping may cost less.

            • The Mytek DSD DAC would have been a great candidate to try an ADuM isolator on its USB 1.1. Or both USB ports. How often do you have something to test with a dedicated USB 1.1 port?

            • Cool. The quality with an ADuM can go either way. It made my Off Ramp worse. On the other hand, there’s a potential for magic. Or voodoo. What I hear on the cheap USB converter is certainly one of the two.

              Is the USB 1.1 on the Mytek async?

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