Mutec MC3+ USB DDC/Reclocker Measurements

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ChitChat:

The Mutec MC3+ USB is indeed a ‘digital to digital converter’ or ‘reclocker’. Taking one digital input format such as AES or USB and providing a reclocked output in AES, SPDIF etc.
But, it does differ from products such as the Singxer SU-6, Audio-GD DI20HE, Denafrips Gaia and other ‘audiophile’ oriented products in that it’s mostly designed for professional use and has some features specifically for that.
This doesn’t stop audiophiles from using it of course! And so I wanted to give it a run through its paces to see how it performs relative to other products.

What ‘professional’ features does this have which other DDCs do not though? Well, there are a few:

  • Internal DSD to PCM conversion (PCM processing is bit-perfect however)
  • Word clock distribution and generation
  • Multiple clock rate outputs simultaneously

Most DDCs do not have external clock support, and if they do, it’s 10mhz only, whereas the MC3+ can take word clock or 10mhz reference input.
It can also then redistribute the word clock via the plentiful outputs on the rear. This is intended for studio situations where many devices need to be synced to the same clock.
This output clock signal can also be generated using its own internal clock.

Rear I/O of the MC3+

But realistically, most users will not be buying a several thousand dollar 10mhz clock to pair with this, so lets have a look at how it performs as a standalone unit.

Before we do though, let’s have a peek inside.

Mutec MC3+ internals


The internals of the MC3+ are functional, but in my opinion do raise a few questions about whether the over £1,000 price tag is justified.
No doubt a significant amount of R&D has gone into this product, but when the first thing you see when opening the device is a bent PSU shroud, and the 2nd is a clearly crooked tantalum capacitor on the board, it does not leave a great first impression.
Especially when there is a green checkmark QC sticker on the main FPGA which implies someone SHOULD have looked at this.
The fact that this must have been seen but considered ‘fine’ is a bit concerning for a premium product like this, especially one intended for professional use where downtime and unreliability is not an option.

Though otherwise, the board is laid out very nicely, with regulators for everything that might possibly need one. And quite clear labeling on many components too! Which may not be of much use to the end user but is quite nice to see.
There is a large FPGA which handles all the main functionality of the device, and next to it you can see the single 1ghz clock that the MC3+ uses.

This is seemingly a proprietary clock as I cannot find any product information about this part elsewhere, but it is odd to find just a single clock rather than two, and moreso one that is neither a multiple of 44.1khz or 48khz.

Typically high performance DDCs will have at least two good clocks, one for each base-rate. As synthesizing a 44.1khz or 48khz clock from a reference clock that is not a multiple of either will inevitably not be perfect.

Clocks in the Singxer SU2 KTE edition. Two large accusilicon clocks and two smaller ones.


But, perhaps this is necessary to allow the MC3+ to perform its task of handling various clock ins and outs at the same time.

Removing the USB board we can see the XMOS receiver chip, and an AKM resampling chip which is used for the DSD to PCM conversion.
On the right, there are some galvanic isolators to prevent any noise from the host device being passed through to the MC3+ itself.

So overall, the internals seem ok, but with a few quality concerns that really should not be present on a product as expensive as this.

BUT, if the performance makes it worthwhile then this can likely be overlooked by many.

Measurements:


Test Setup:

– Audio Precision APx555 B-Series Analyzer
– AudioQuest Carbon Coaxial Cable and AES cable(1.5m)
– Intel PC via ifi iGalvanic 3.0 and iUSB 3.0 as USB source
– 44.1khz and 48khz real music played through device during measurement
– Coax output used unless otherwise specified

Jitter:

To measure jitter, the device is connected to the digital input of the APx555, and the analyzer is set to analyze jitter, not audio content.
These measurements do not show audio/analog info, but instead show the spectrum of jitter, ie: time-domain inconsistencies.
This is the primary factor that a good streamer or DDC will seek to improve.

44.1khz Jitter
48khz Jitter

Not off to a great start….
Jitter via the coax output of the MC3+ is very high, and is beaten by all the other DDCs I have tested so far by a comfortable margin.
However, the AES output was much better.

AES 48khz Jitter
AES 44.1khz Jitter

Now performance is starting to look much better. But, it’s still not all that great. And is around the same as the $199 pi2aes streamer (which also features I2S output):

Though interestingly whilst peak and RMS values are similar, the pi2aes has much less deterministic jitter content.

Noise however, is absolutely fantastic.

Worth noting that sometimes a switching PSU can reduce leakage in the 50hz/100hz areas at the expense of causing increased ultrasonic switching noise, but overall, seems to be doing great.

So it seems that as a standalone unit, the MC3+ definitely does its job, and does it quite well. If you need good performance with huge flexibility in clock distribution and I/O, then the MC3+ is a great choice.
But if you’re wanting the lowest jitter digital source for your personal listening setup, then other products provide better performance for the same or less money, and will feature i2s output which the MC3+ lacks.

Either a DI20HE or Singxer SU6 could be purchased, both of which boast RMS jitter about 50ps lower and peak jitter about half of the MC3+. Even if you need SPDIF input, the DI20HE can do this so you are not restricted to USB only.

So to conclude, I’d recommend the MC3+ if you specifically need the featureset it offers. But for your own listening in a normal audio setup, there are better products to buy.


Daisychaining:

One thing that it seems some users of this product (and other mutec reclockers) take to doing, is not just using one, but buying several and daisychaining them one after the other.

In fact, Mutec themselves have a page where they advocate doing this: https://www.mutec-net.com/artikel.php?id=1388254422

This was a bit iffy for a couple reasons, firstly; if this did provide a demonstrable benefit, then Mutec of all people would have the test equipment to demonstrate this. Not even necessarily to show whether the difference was audible, that’s an entirely different question. But just simply to show that four of these in series does in fact have lower jitter than just one. Then people can decide for themselves if the difference is audible and worth the added cost.
Instead the page talks purely about the subjective findings which were not done in any controlled manner at all, and being that they are from the manufacturer, who I’m sure would love for you to buy four of their products instead of one, is not exactly unbiased.

“With two devices, I found the difference already uncomfortable, with only one stage unacceptable and the bare DAC as a source sounded to me like I would rather stop listening to music.”

This quote stood out to me. Are Mutec themselves saying that just one sounds bad?

And secondly, this simply isn’t how reclocking works. Reclocking implies clock decoupling, putting information in a FIFO buffer and re-transmitting using the device’s own clock. The timing with which data is put into that buffer does not matter so long as it is not so bad as to cause buffer underruns or overruns (where the buffer becomes full or runs out of data).

It does not get lower with each successive reclocker, and jitter performance will be dependent on the last device in the chain.

Anyway, just to see for myself I did try both feeding the MC3+ from the APx555B’s own advanced digital I/O output via AES. And also even tried a daisychained stack of KTE SU2 -> DI20HE -> MC3+ USB.

In both instances, jitter performance was the same as or slightly worse than just connecting the MC3+ via USB. And was still not as good as just using a DI20HE or SU-2 standalone.

‘Triple Reclocked’ Jitter 48khz from MC3+
‘Triple Reclocked’ Jitter 44.1khz from MC3+

So please, do not purchase multiple DDCs/reclockers to daisychain them. You will not get an increase in performance and money would be much better spent buying a better DDC, or upgrading other equipment in your chain.

3 thoughts on “Mutec MC3+ USB DDC/Reclocker Measurements”

  1. Your measurements are quite valuable but I don’t understand why you give strong advice on something that you have neither measured, not heard.

    I had one Mutec MC+3 UBS when a friend, who had two, brought them over. We tried one/two/three chained. The first fed from SOtM SMS-200 ultra and connected to each other by AES/EBU. The second unit gave a very clearly audible advantage, I’d say another 50-70%. The third one another 20-30%. I know these percentages just arbitrary.
    This was repeatable and also worked the other way round as we started removing the units one by one. I ended up buying a second one and have not regretted it. (Plus added a Mutec Ref 10 later and also removed the SMSP and use LPS now in the units.)

    When I asked Christian Peters, the head engineer at Mutec, in Munich 3 years ago, why this is happening, he said, he had no clear answers, but about a dozen people came to him at the show asking the same who also had two or more units chained. Perhaps the re-clocking process will result in lower jitter when the incoming signal has lower jitter too. I know it makes little sense when the input signal is USB and is asynchronous but then why do the SOtM SMS-200 ultra and the txUSB ultra have expensive re-clocking panels in them, not to mention several high-end USB PCI cards that put emphasis on their low-jitter clocks?

    Reply
    • Because it simply isn’t how reclocking works.
      If there were a proprietary link/protocol between the MC3+ units then yes that’d need further testing, but there isn’t. It’s using standard SPDIF/AES and so the effects of stacked DDCs or even just any SPDIF source vs USB can and are demonstrated above.

      Even as you said, the Mutec engineer has no reason why it’d make any improvement. But I’m sure they’re quite happy for people to be buying 3-4 of their products instead of just one.

      In regards to the test, I’m not discounting what you heard but I’m guessing that this was a sighted test.
      If someone is happy to lend 2-3 MC3+ units I will test the daisychaining (both measuring, and I’ll listen sighted and blind) and if there is any demonstrable improvement I will give them $1000.

      This simply isn’t how reclocking works and whilst it’s not what owners of 3-4 MC3+ units will want to hear, the likely truth is that it’s just expectation bias. It’s an immensely powerful factor.

      Reply
      • I know what expectation bias is. I spent way too much on this hobby, I ‘expect’ things not to make a difference. I was a reviewer for a magazine for years and didn’t buy most things, very few, in fact.

        I hope you’ll have a chance to test two units in the future or just out of curiosity chain two DDCs of different brands to see if there is any difference. Perhaps in AB and BA order. You only need a cable…

        Reply

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