USB connection to DAC: multi stage improvement

Berkeley Audio Design excludes USB connections from their DACs to protect the delicate digital-to-analog conversion circuits from computer-generated electrical noise and clock phase noise. They believe that connecting a DAC directly to a "dirty" USB source inevitably degrades audio performance.

@jmrrobbie1 - I have read and heard about the detriment of USB connections from others, in addition to Berkeley.  Interestingly, Aries Cerat has just released a $12K interface (Hronos-Project X) (link) that accepts a USB signal and feeds their DACs a customized discrete signal on a board that replaces the USB input board.  They imply it makes the source/streamer quality mostly irrevalant and that it achieves a level of sonic improvement that is comparible to upgrading to the next higher DAC in their line-up.

Because I use two different DACs in my main system, it has been easier for me to route a high quality USB output into a DDC, which can then route two separate (non-USB) signals to the two DACs. 

After reading conflicting reports about which inputs sound best for my DACs, I tried comparing the AES or S/PDIF rca inputs on my DACs (output from the Singxer SU-6 DDC) to a direct USB input (output from my Sonore Sig Rendu SE Deluxe Opt. streamer).  The results I heard were close and I concluded the USB directly from the Sonore sounded very slightly more fluid. 

After researching the SU-6 as well as reading more about the pros/cons of USB vs. AES or S/PDIF, I have decided to try again with the supposedly higher quality Berkeley Alpha USB Reference Series interface, which I now have on order. 

There is so much to this digital source issue, including the network capabilities and isolation, streamer quality, interface choice, and of course the DAC itself and how well it is optimized for a particular interface.  It seems there is clearly no one-size fits all approach.

Just a comment on DDCs: the principal benefit of USB connections is that the DAC‘s clock slaves the server. So unless the DDC‘s clock is as good as the DAC‘s (unlikely unless the DAC is cheap) that benefit is lost. The problem with USB is it‘s proneness to incursiins of noise via the 5V line and picking up noise elsewhere due to its two way protocol (ground, RFI/EMI). Hence the effectiveness of galvanic isolation in decrapifiers. What I am trying to point out is that clocking and noise reduction need different measures

"Highly sensitive to clock phase noise. Direct USB connections can introduce this jitter into the DAC’s master clock, reducing sonic clarity".

@jmrrobie1 Hi, they fed you confusing marketing blurb here: clock phase is one thing (frequency related), jitter is another (time domain related).

@mitch2 +1 

“It seems clearly there is no one-size fits all approach.”

Congrats to the OP for their persistence/diligence in pursuing their sonic goals. 

I do want to comment briefly that the approach taken by Berkeley Audio ‘Designs (convert USB to SPDIF) was developed quite a few years ago. There is no question of the superb performance of their DACs. However, USB interfaces have advanced markedly in that time. So has the availability of hi-res content. Those factors make USB more attractive to me and many manufacturers. While it used to be orthodoxy to prefer SPDIF or AES EBU, that is no longer the case.

In my own use case, I’ve recently acquired a new streamer in one of my systems (Synergistic Research Quark) which can be used as a roon core or to output digitally. I compared the stream via Ethernet to the renderer built into my DAC (works great) vs its output via USB into my DAC (even better). FYI: The only digital output offered by the Quark is USB. (Same for the JCAT S1 Evo under consideration for one of my systems). 

A relevant tangent:  surprising to me, I am now happily using Roon for library and streaming management with the Quark. Some may recall I’ve been critical of Roon in the past for its sonic penalty. 

Things change, technology advances and the complexities of making the nearly unlimited variables in our respective gear work seamlessly (it often doesn’t) mean that an approach that works well for one may not work well for another. Absolutes I once held are now easily disputed by my own experiences.

Plenty of great comments in this thread, shows how good this forum can be. 

(that's a thumbs up, not a hand shake icon)

I will confess, all this digital stuff makes my head spin. I have no interest in even attempting to understand how/why because it would take decades, and then I'll not even know 5% of what some of the experts already do. I will trust some of them instead. (the two mentioned below are on my list) 

@mitch2 

Interestingly, Aries Cerat has just released a $12K interface (Hronos-Project X) (link) that accepts a USB signal and feeds their DACs a customized discrete signal on a board that replaces the USB input board.  They imply it makes the source/streamer quality mostly irrevalant and that it achieves a level of sonic improvement that is comparible to upgrading to the next higher DAC in their line-up.

Not sure if there is any optical isolation in Stavros' solution, but sounds alot like what Andreas Koch has done with his MPS-X or USB-X4 isolators. 

USB-X4 Purpose:

this simple USB to PLINK interface is designed to isolate any USB source from the sensitive DAC via our high quality, synchronous fiber optic PLINK connection. It borrows this concept from it's bigger brother, the MPS-X, which is not just limited to the USB interface like the USB-X4, but also includes a variety of other interfaces and features as well (see MPS-X product page for more details). Any digital source with a USB host interface can connect to the USB-X4 which then is connected to any of our DACs(*1) through PLINK. All asynchronous clocks that are mandated by the USB interface standard and any other digital noise from the source are therefore kept from entering the DAC where they would always cause some audible deterioration. Asynchronous data streams from the USB source are carefully filtered with our PDFAS algorithm and synchronized to an internal high quality audio clock. This results in a dramatic sonic improvement when compared to a direct USB connection to the DAC. The sound stage becomes even more defined, the performance even more liquid and overall more "analog-like". A valuable addition to any of our products