The DDC and Digital Reclocker thread

I put a DDC between my SOtM bridge and my Amber 3. This is a $1500 bridge with a good onboard clock… still, the DDC still made a noticeable difference??? There was a noticeable improvement in instrument separation in particular. Nothing else really changed a lot even though it all sounded better but it was the instrument separation that really stood apart. So it seems like there’s a lot to be gained by getting off USB even at the higher end.

USB for audio suffers from two things, 1) USB noise from the power chain itself since noise generated in your PC can be introduced into your DAC via the USB cable. 2) The time domain which is muddied by USB audio signal needed to be converted into I2S to communicate with the DAC.

We take care of the first issue by separating (external) power supplies, galvanic isolation via USB decouplers, however way, it all helps, yet still they do nothing to address the second issue.

DAC’s commonly re-clock incoming USB signals, they sometimes regenerate it entirely, but most often they correct it with a PLL They still have to have a clock though they aren’t asynchronous devices. ref @Polygonhell You see the clocks in this Amanero 384 USB (which is in a lot of decent mid to higher tier DAC. Or Shiit’s very own UNISOM USB, another well regarded USB implementation.

So if via USB the signal is regenerated or cleaned up before it’s sent to the DAC why do I see improvement? DACs only speak I2S they don’t speak USB so anything coming into the DAC via USB needs to be converted. Perhaps it’s this point that seemingly is an Achilles heel?

The SOtM I referenced above doesn’t suffer from USB noise coming from power (unlike a dirty PC environment). I have a very high quality ifi Power Elite feeding it, and the SOtM cleans and re-clocks the signal it sends out to a DAC, but it only sends out that signal via USB. Yet still there’s performance improvement when you re-clock regenerate this already clean signal. So what’s in USB that is inherently noisy?

There are other streaming bridges like the Pi2AES that perform this same cleaning (re-clocking) up of the signal but they send it out via I2S or AES/EBU, BNC or SPDIF Coax. So it bypasses the USB to I2S conversion.

The difference is if you send via USB, the DAC is responsible for the clock, if you send via anything else the clock is on the wire and for everything except I2S has to be de-multiplexed out of the signal. ref @Polygonhell This may also explain why often people claim that an I2S out from a re-clocked signal to an I2S input in your DAC is “the” way to go. But it also goes to show that there’s clearly room for improvement in a lot of DACs by getting off of USB altogether even if you’re already giving it a clean re-clocked signal as in my case. Perhaps it also explains why things like the Pi2AES sounds so good to begin with for the price range. It’s simply not burdened to begin with.

Clearly the ultra high end world solves these issues but we’re talking upwards of $5k DACs and well into the price of a small 4 door hatchback. But for gear less than that, try to move your gear around. I had my DDC sitting unused in the closet and what do you know? A nice little upgrade to my 2 channel stereo for zero dollars spent.

Hopefully we can use this thread to combine a lot of the disparate conversations about DDC in the site and have a good central point for discussion so feel free to add your experiences or correct stuff that’s not entirely clear or accurate in my write up.


Exactly why I picked up a Matrix Audio X-SPDIF 2, to sit between the PC and DAC allowing me to convert USB and feed the DAC via AES/EBU. I was using an Allo DigiOne for this purpose, but that was limited to coax/spdif though an improvement it was not the best use of that device - also being that I use it as a roon endpoint too, a bit redundant when there is a PC so close already that functions as an endpoint. Also, the X-SPDIF 2 does much better cleaning the USB and re-clocking. I now want to get a couple more of the X-SPDIF’s or another DDC appliance to use at my secondary listen desk and my 2ch space. The difference in sound even before getting ifi xpower and better than bargain basement USB cables was very apparent - which I attribute to the re-clocking primarily. And my DACs (Soekris) already had better than the norm USB implementations.

There are factual inaccuracies in this.
It’s not mile off but.

The big difference between USB and the other inputs on a DAC, is that there is no clock in a USB signal. The USB circuit in the DAC provides one.

All the other digital inputs on a DAC do provide a clock from the source, with I2S being considered the best, because the clock signal is separate from the actual data, on everything but I2S, the Input has to extract the clock from the data.

Even on AES/SPDif etc, DAC’s will commonly either correct the clock with a PLL or even regenerate the clock, some usually higher end DAC’s will allow you to disable this correction.

The quality of a USB signal on the data lines is unlikely to affect the sound of a DAC, it is almost certainly decoded perfectly by the DAC and clocked accordingly. It can have errors since there is no error correction, but in practice they will be extremely rare.

The USB signal entering the DAC on better DAC’s will be galvanically isolated from the signal to the DAC. This isolation is likely not perfect, and the the thing reading the USB signal itself and converting it is probably putting out it’s own noise.

What USB to USB DDC’s can do is add an additional layer of galvanic isolation.
One that converts Network to USB can go further by simply introducing less noise that needs to be isolated than your PC does.

A DDC that converts USB or Network input to say SPDIF or AES or I2S can go a step further because it generates the clock and if it can do a better job than the USB device in the DAC it’s a win too.

I also suspect that most Network transports are more complex than just a DDC, i.e. they apply their own filters to the input signal, I know for example that the Aries transports skipped some of the processing when using Roon at one point (since fixed) and RAAT was considered inferior on the native Lightning protocol and even DLNA.


So in my example the gain is coming from the clock on the DDC going to the DAC via SPDIF is a better overall than the SOtM clock going into whatever the internal USB module on the DAC is doing there before it sends it to the DAC?

SOtM also makes available a better re-clocker, the SOtM tX USBultra. Which is supposed to have a better clock and from what I’ve read further cleans up the signal as well. However it too only has USB out. It would be an interesting thing to compare.

I own the SOtM tx USBultra, without reclocker and the SPS500 with silver cable and love it. The combo makes a noticeable and immediate difference and I am also using it to the Amber 3 with Amanero

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So if a dac doesn’t have a “clock off” feature, the re-clocking benefit of a DDC is lost?

Curious to see @Polygonhell response, but I don’t think that’s the case. It seems with clocking, the better the signal in, the less work any clean up that happens has to do. So it’s a GIGO scenario. Good clock is good clock. (perhaps maybe the only exception maybe if it goes into a USB where you don’t get the most bang for the buck.

Would like to see some numbers… help me ASR, you’re my only hope. lol

I think the SOtM tx USBultra i s ONLY a re-clocker as it’s supposed to have a slightly better clock than the SOtM SMS 200 Ultra built in clock.

No because you can only time correct a signal that is close to correct to start with.
But if you have an input signal with a very high quality clock, sometimes disabling the PLL on a DAC that allows it will produce an improvement.

In fact I think @M0N runs multiple reclockers in series, and hear’s a difference in doing that.

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Ah yes, I meant to say it is the USB reclocker/regenerator, but I don’t have the Master clock input option (in case I wanted a dedicated clock)

That SOtM master clock is mucho dinero.

Too much for my blood (for now).
Which USB cables are you running on your reclocker and on your DAC?

From the Bridge to the reclocker a short Silver Dragon. From the Reclocker to the DAC a SPDIF Coax (Audioquest Cinamon I think?) I’m looking to maybe change from SPDIF to AES/EBU although I don’t know how much of a difference that may make. You know, just screwing around with cables.

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Ofc YMMV, but I felt after I added the SOtM combo in, I have noticed more of a change in USB cables. If you dabble some more down the line, make sure your best cable is after the reclocker (you want to maintain that clean signal).

Might experiment a bit, on both occasions that I’ve gotten off USB on the Amber 3 I’ve perceived a change, didn’t think it was cable related but who knows. The Silver Dragon USB is the best thing I have in the house at the moment, maybe I’ll try experimenting with something further upscale. I always assumed the USB input, it’s a pretty noticeable bump like I said in the OP.

One can never leave well enough alone right? lol Certainly not in this hobby.

So I’m going to ask a potentially stupid question. Why bother with USB at all? Use a streamer and go I2S/AES/Coax to the DAC.

The SOtM is USB only out. The DDC corrects that. It’s the amount of correction that surprised me since it’s already supposed to be a clean platform with a good clock on board.

Yes I do, but it doesn’t always make sense to do that (and while it may improve the sound, it’s not going to be as massive of a jump doing so, like assuming you have equal quality reclockers, and this is highly dependent on the setup anyways, if adding one gives a 100% improvement, adding the 2nd one in chain might give 120-150% total, it’s not going to double performance if you get what I’m saying. All depends. And you want to make sure the best ddc is the one that is last in the chain imo if you are chaining

Currently on my main desk I run USB from my pc to an Ideon 3R Master Time blackstar, which then via it’s usb out goes to a totaldac d1 digital mk2 reclocker, which then gets sent over to my aes distributor (which can reclock if I let it, but I found that in this case enabling it either gave no difference or felt slightly worse since I already had a better clocked signal). So PC (via usb) → Ideon (via usb) → totaldac (via aes) → ati (via aes) → DACs. In this setup, I can also take the streamer at my desk which is a dcs network bridge and run it into the totaldac via it’s aes in, so that improves the streamer as well.

Something interesting I’ve found is that while in my experience adding more unneeded or extra things in an analog signal path is seldom positive, chaining things together and multiple recolocking/regeneration/isolation in digital signals has actually been positive changes. So that’s been a weird trip tbh

On the idea of USB vs spdif formats, personally I’ve heard good results with both. Depends on the gear at hand, a well implemented usb can be further improved by a good usb streamer or reclocker, and same goes for using spdif/aes. So all depends on the design, and I wouldn’t make any blanket statements, just depends on your setups

I am going to try something absolutely stupid when I get one of the denafrips in I ordered along with the term (the gaia), which would be this chain

PC → iFi iUSB3.0 → JCAT USB Isolator → Teddy Pardo TeddyUSB → Ideon 3R Master Time Blackstar → Berkeley Alpha USB → ATI DDA212-XLR → Denafrips Gaia → Totaldac D1-Digtal-Mk2 → DAC

This is bound to either not work, provide no benefit, and is simply for experiment purposes and personal curiosity to how much shit I can chain in and what happens. I’m sure I could look around more of my house to find more shit to chain in (I guess I could throw my eventide h9000 in there for no reason whatsoever), but this is all for shits and giggles and not anything serious. Still want to try it though

Depending on the dac, sometimes it makes more sense to disable internal PLL or reclocking, sometimes it doesn’t. But typically with any high end dac, a moderately nice ddc/streamer/source will give some positive benefits. But on some of the really high end dacs, sometimes you might find the internal solution to give better results than your current digital source either because your digital source ends up being worse than what the dac can correct or do on it’s own, or it bypasses some sort of processing. But the majority of the time a nice digital source is an upgrade to most higher end dacs, with varying levels of quality jump

:rofl: :rofl: :rofl: :rofl: :rofl:

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I figured I might as well try something stupid if I’m presented with the opportunity lol. I can’t image it going all that well, but oh well I’ll have to find out when I get to it

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