Modding the PS Audio Directstream DAC MK1 and MK2

The internet can be a weird place. I've generally seen negative comments about PS Audio DACs outside of the PS Audio forum so it's a little surprising that you've tripled sales after moving away from the forum. But it is possible that the website helped people feel like the transformers are more of a business and not just a thing where you message some guy and hope to get something back after dropping $600+. 

Agree. Thanks for posting this. We feel these transformers are a much better investment than say $1000 power cables and it’s immediately noticeable and measurable.

The MK1 upgrade makes a lot more sense for many instead of the large investment in the MK2 which they still have not moved past Beta testing even thou they are and have advertised it as a "ready for market" product however we feel the MK2 transformers are a must over the currently configured Edcor’s being fitted in the MK2.  Look at the sweeps we have done of each.

If I had to rate the value of audio products purchased or mods I've done over the years, the APS DSD MkI mod is at the top of the list. It transformed a decent DAC into a total beast. The value proposition is off the charts. 

Hello folks, still here occasionally :) Thought I'd share some things.

The Vocm mod with JK high nickel trafos is quite good and would likely satisfy the majority of listeners IMO.

I will say though, the pinnacle of DS DAC mk1 sonic performance is, Diff amps topology mod (also found some diff amps I prefer to the AD803x), along with a bi-polar PSU that then allows for no caps or trafos on the output. This also allows Vocm to be=ground, so no mod needed for it anymore. It's not trivial to do but can be done, I'm listening to mine here now with it.

Now we're really talking, now there is no audible distortion (quite rare IME) and you are hearing the fw performance basically. Any further improvement would be upgraded fw. I asked if we could get a Mk2 version improved fw for Mk1 and the answer was no.

BTW I prefer the older Sunlight fw on mine; it's more open and dynamic and alive sounding. It's playing here now. 

I recall someone on the forum had done some topology mod effort, but they claimed they didn't like it. I don't know what the problem was there, and maybe I had also misguided somewhat with some poorly suggested values at the time. But whatever, I don't have the time or energy these days to try and maintain and acceptable S/N ratio of a web forum and that's when I called it quits there basically. The truth of it is what I posted above.

TK

Some other news, this summer I was able to get Tom C of Neurochrome Audio to do a special version of his Modulus "error correcting" amp boards (thanks Tom!). Notably, we eliminated the OA input buffer, and the input coupling cap (and feedback cap!) and added back a DC servo since its now DC coupled. IMO this should allow the most transparent Modulus you can do basically. I’ve been listienng to it for months (its playing here now with a new proto preamp) and it’s quite good in fact. Note that, with the OA input buffer gone the boards are single ended input only, which is fine. The amp modules themselves are also single ended anyway, as most amps are internally. And again, its fine.

However, for best results it does need the best OA we can manage for the "error correcting" portion, and for the DC servo. Most industrial OA are evil in comparison; discrete ones generally less so at least. I socketed my build and prefer the Sparkos SS3602 in the error correcting location and a Muses01 in the DC servo. Muses OA appear standard old industrial but they are far from it, employing a Cu leadframe for example. They put a lot of effort into these in fact and you can definitely hear it. The 01 is a JFET input and is very clean and quiet, also good for a DC servo IMO. The 02 is a bipolar input and "rocks" a bit more in comparison IME. But not as good for a DC servo due to input bias currents.

I have mine in a Naim NAP180 chassis with what I call a "super" PSU in it. I think I would recommend a good SMPS for it if DIY. As Tom says, with this much error correcting horsepower available the boards are somewhat immune to PSU, but still, better PSU is better in general.

If you want to DIY your own, ask Tom for the "Todd King" edition Modulus boards. I can recommend them.

TK