Budget ddc between mac mini and naim dac

So I’ve been using an xmos based budget usb to spdif converter (douk u2 pro) between a 2018 i7 macmini with roon and a 2010 ndac. This goes into sn3+hcdr.
Cable from mac to xmos is ugreen “printer cable”, mogami coax from xmos to ndac, chord signature from ndac to sn3.

Sounds satisfying, the recent uplift of the hcdr was very noticeable for me, especially in the bass region where I most appreciate it.

I’ve been investigating my next upgrade and can’t justify at this point more than 250€, as the hc is very recent. I think the lowest hanging fruit in the chain right now is the conversion to spdif, as computers are known to be noisy and to pass that noise on to their usb output.
So I was pondering if there was any way to make the output of the spdif interface look more as an nd5xs2 to the ndac. Without the sizeable outlay that is.
I’ve been looking into usb isolators ( ADUM4166 based less than 80€), also upgrading the clocks on the xmos spdif converters, and finally buying separate lps for both units, 75€ at audiophonics.
But truth is I have no idea whether any of this would work with the ndac. It is my understanding it relies on its own clocks, and maybe isolation is already there (i eant to use coax because of optical limitations, although I guess isolation is best on optical)
So the question is: what would be the most sensible upgrade, if any is possible within budget?
Or maybe change the approach, get a different ddc? Amanero based maybe?

Thanks for reading this and any help you can offer.


If you want to totally galvanically isolate the MacMini from the nDAC, there are loads of USB>Toslink cables on the market. So the optical connection will fully isolate any electrical noise between the two assuming that optical lead doesn’t use a conductive mechanical shield or metal Toslink plug (some do but it’s rare enough to assume they don’t).

Just be aware that optical will limit the maximum bitrate far more than a coaxial or USB connection. It will support hi-res audio but not to the same degree. Best check the nDAC manual for it’s maximum supported bitrate over optical.

Generally, I prefer optical for connecting anything potentially noisy to a DAC. But if I was in your shoes, I might choose to do nothing and put the money towards a dedicated streamer even if that is 1-2 years away.

There are numerous USB to digital converters a huge range of prices, and price is not necessarily any indication of performance. There have been some comparative reports of some on the market in various places, certainly I’ve seen such somewhere a few years ago (possibly Audio Science Review?), and there has been some discussion of such devices in the current thread impressions of the Chord Qutest, however performance into a different DAC might not necessarily apply to the nDAC.

A whike back I used a Gustard U12 which I found very effective (into Chord Hugo, a DAC known to be very susceptible to superimposed RF) but didn’t compare it with anything else. That instance was feeding from a Mac Mini running Audirvana, fully optimised including using a dedicated USB bus within the MM, playing files stored in the MM: That setup performed better than the same Mac Mini used as a NAS (Serviio software) into an ND5XS as “transport” feeding the Hugo, though in terms of difference it was marginal not orders of magnitude, as indeed one might expect.

A silly question perhaps but does your vintage of mac mini have an optical output? If I remember correctly, many generations did via a dual use output port.

Best regards, BF

IIRC, Apple dropped the optical output from mac minis around 2014 and definitely gone by 2018. A shame IMO. I used optical from an early Mac mini, run headless, into nDAC and it was rather good. Slightly better indeed, at least to my cloth ears, than my CD5XS into nDAC.



Best ddc I’ve used was Berkeley Alpha. Not budget but worth every penny. Not a bad option is Sotm with a clock and power supply upgrade.

Thanks for those suggestions, those are new to me.

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Yep, 2018 has no optical out. I’d rather avoid the 92khz limitation though and that’s why I prefer coax.

Dedicated bus? Tell us more! What is the principle behind that?


My Mac Mini is a “late 2012” model, and has an optical output. Received wisdom, however, with Audirvana was that the latter’s “direct mode” bypassing the Mac’s own sound circuitry and drivers and reserving a USB bus just for the audio output offered better inherent sound quality - however I haven’t compared.

That’s understandable. When I was using a Mac mini it was with files ripped from CDs and Hi Res wasn’t really a “thing”.

Mind you, although I usually buy downloads in the highest quality I can, I’m not sure I can reliably tell 96/24 from 192/24 for example.


Thanks for your answer. I am using roon in fact just for the convolutional filter support as I got some HAF filters. Those were made to remove some nasty room modes, which they successfully did. So I am a slave to roon at the moment and the idea of inserting a streamer to use as just a roon endpoint to get a decent coax spdif sounds not the most efficient.

I don’t know if there are streamers which could apply a given conv filter? (Not standard room correction such as dirac etc)

Otherwise I’d like to keep within my limited budget and get the best sound per pound possible optimizing the signal in between mm and dac.

My doubts as well have to also do with the particular implementation of the naim dac. It serms it does not rely that much on the external clock received through the spdif input but on local clocks. That made me think that maybe inproving clocks on the usb to spdif converter might be useless.


I am no expert on either the Mac’s design or Audirvana’s internal workings. I assume it means that there are different USB buses within the Mac’s architecture (3 rings s bell from somewhere), and that Audirvana’s coding is such that it can ensure that its output and nothing else can use one, any other USB functions being routed via the others. For more info you’d probably have to research Audirvana.

I have no knowledge as to how true or what actual effect they may be, but it made sufficient sense to me to not question the claim, while sound quality is very good.

Ah, I understand. I imagined an external usb device which it is not.

Intona 7055c USB isolator. No reclocking, but it’s a lab grade solution. I love mine.

Interesting, thanks, do you use it in a chain to feed an ndac?
In the systen in your profile I fail to see where the isolator would fit, but not familiar with the inouts of an ndx2, does it accept async usb? Or did you use it maybe in a second or prior system?


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Audiowise SRC-X - I wrote here in the forum about my experience lately and I have a very similar setup as yours. Sorry I don’t know how to link my post…

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I actually used it in my prior Chord Qutest setup that fed my SN3.

Roon Nucleus+ → Intona → SRC-DX → HPF BNC Filter → Canare L8-CUHD 75r BNC cable → LPF BNC Filter-> Qutest.

Transitioned from that to my current NDX 2 + XPS-DR.

Yes, the Audiowise I believe mostly made for Chord dacs as they have 2 BNC inputs and than it can upscale to 752 hertz.
The Ndac SPDIF input anyway is max of 192 so I use just one BNC cable. I upscale from Audirvāna. The results are amazing and better than CDX2.2+xps2 I had.

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I will try to upscale from roon and see what happens.