Modding the DirectStream DAC MKI

The output stage looks impressive.

Though it’s so weird that you’re talking about an ultimate upgrade but you’re still using the mediocre stock power supply. Even this inlet with “filter” that chokes the power… seriously?

I guess you are from the camp who don’t think that power cords, hook-up wire, and power supplies matter, aren’t you?

But from my experience, all this does matter a lot. Because (I said that before, and I will repeat again) through your improvements you’re not only can hear more details in the music material, but you can also hear more noise from the power supply!

It going to be a speculation, but just saying… probably… the stock analog board but with a thoroughly upgraded power supplies (*upgraded main power supply board, and an additional PSU for the analog board) could beat your “Studio DAC” if it has a bad power supply part.

I hope I’m wrong, and in all versions of your Studio DACs, you took great care of the power part. But I have never heard of that part from you. And I read all 5540 messages in this thread.

You are always talking and bragging about weird professional concept mods (opamp swapps, oscillators and their power, output stage, etc) for a very narrow circle of people. While the simplier mods laying on the surface (well, of course, this depends on how good one at soldering) would give improvements for this DAC without changing its original structure. With mods discussed in this thread, we’ve been trying to hear the best version of Ted Smith’s DirectStream DAC. And you’re trying to build your own DAC using the parts of this DAC.

Sorry for the many letters… Don’t get me wrong, I admire all your concept ideas (even if I don’t understand them to a full extent).

What I am asking here is what mods have you tried for the stock power supply board?

Look closer- you’ll see there’s a new PSU in there for creating the new bi-polar output stage PSU :slight_smile:

The stock PSU to the analog stage is good. It’s not noisy, it uses a high performance discrete regulator along with some passive input filtering.

And regarding the stock output stage- it beats nothing, no matter how good the power to it is.

It appears you haven’t read that much really. Way back I had created a large, mostly passive new bi-polar PSU for the output stage, etc. Most don’t get that far from what I can see. There are several issues that come from doing that, including a serious power on crowbar issue that can burn things. I haven’t seen anyone else mentioning that yet. I did it so we could get rid of the output DC blocking. That version DAC is playing here now in fact.

Try these things yourself and see for yourself. And don’t be so negative FFS.

Please pardon me, I didn’t mean to be negative or rude.

Of course, I saw it. But, having a dedicated PSU for the output stage doesn’t fix the noisy stock PSU. And you have all the noise from the input board, and the display/processor board in your superior output stage.

Many would disagree. Even though, there are regulators and filters on the analog board, they have a weak power to regulate from the stock power supply. When you have good separate power supply it’s easier for these regulators and filters when they’re dealing with better input, so they giving better output. It’s easy to hear when you have a dedicated power supply. A dedicated power supply for the analog is the way to (at least to try to) isolate analog and digital power. This one is the easiest mod and a must-have.
(That’s why many didn’t like the sound of the Bridge II card. It sounds way better if one fixed the power in the DAC. But this is a whole another story. )

I did see that. But, again, it’s all about the modified output stage. After all, it has nothing to do with “mortals.” Thus, nobody reported their experience with that mod.

The stock PSU has to be fixed before you go that far.

There are so many simple mods that you can do, and you haven’t even tried them, have you?
Like, (already mentioned) separate PSU for analog, changing rectifying diodes, changing regulators, separation power of the display/processor board from the one for the input board, changing wiring, etc. Just throw away this stock inlet FFS and install one from Furutech.

With your conceptual mods, these simple mods should give more obvious changes. I mean, compared to people who didn’t power supply mods before the analog board mods.

One more thing.
If I were you, and I have that specific equipment you have, I would see objectively (vs subjectively when you listen for changes) how to add a shielding between the analog board and PSU. Many installed aluminum one, and this doesn’t make any sense. It doesn’t work, of course.
Ted Smith said that the later power supply has shielded transformer because without shield 60Hz and its harmonics get into the output (he said, for some weird reason, more on the left /furthest from PSU/ channel).

As I said, it was just a speculation to make a point on how important good power is. I mean, of course, stock output beats nothing.

Now, my question without speculations.

JKRichards did a great objective instrumental comparison of different output transformers. He measured: frequency response, phase shift, and attenuation.

Can give any objective characteristics on your output stage vs. one with APS transformers?


Well ok, you seem to have a lot of thought and expertise with it, so why don’t you list and suggest how all the PSU issues you’re concerned with should be addressed? I’m interested. TK

I already posred, what 100% work. Still working on something else.
I’m looking for a spare stock power supply for experiments. I’m looking already for 7 months, but nobody offered. I posted a request on the marketplace.

Finally, JKRichards admitted (in his Audiogon thread) that for the DirectStream DAC to sound good, it’s not enough just to swap the transformers and do the simple Vocm mod. You need a good power supply for the analog board.

People here (including myself) already installed these power supplies 2-3 years ago. And previously, Jeff argued with me that he could NOT hear the difference with the additional power supply vs. without. Now, he can hear the difference!

Now, waiting [another 2 years?] for Jeff to admit that the stock power supply needs to be modified for all these mods to really showcase their best. Because the stock awful noisy power supply is still there in his “Signature Plus” version of DirectStream


I would love it if somebody would sell a replacement PSU board for the whole right hand side of the DS. Just make sure it supports 230V though please. You can use the space originally reserved for the Bridge too.

They’re all the same EU/US. Voltage selectable with a jumper(s)

I mean a better one. An Anton-approved one. An upgrade. A mod. Just in a nice simple swap-out-the-whole-right-hand-side package. :slight_smile:

You don’t understand that this power supply board is a hub between processor and input board. You can’t swap with another PSU. You have to work with what you have.

I know it’s not easy, not a DIY thing. But it’s “just” a PCB with components on it. It could absolutely be replaced with a different PCB with different components that do the same job better.

Don’t mind me, just dreaming out loud.

You can dream about it, but if you’re not going to do this, just stop trying to challenge me. Okay?

Actually, I think we’re allowed to be casual dreamers around here. It’s your tone in that last message which is more likely to be seen as out of place.

You’re a smart and capable guy. I encourage you to try being a little bit of a kinder one too if you can.


Engineers are not always people persons :shushing_face:

I have no hesitation in acknowledging you have skills in electronic engineering and I do not – any challenge you perceive in that respect is mistaken.

But I am a systems guy, and part of my expertise is being able to think broadly and explore alternative ideas. That right-hand board consists of a power supply (which the consensus seems to hold as a weak point in the system) plus a comms path for the display/control board to the digital board and some I2S lines for the Bridge module. The only thing preventing a full drop-in replacement kit being available, with a power supply for both analog and digital that Anton Himself would be pleased with, is economics. With some amount of money, it could be done.

It is a completely valid exercise/amusement to float that notion and consider whether the economic barrier is actually insurmountable. I “challenge” you to be OK with other people doing that, even if you don’t consider it worth spending your personal time and attention on.

Yes, you are right. It’s economically impractical to make a new power supply worthy DirectStream DAC. PS Audio came to this conclusion, back in the day, when they developed DirectStream DAC. They added the old power supply from the PerfectWave DAC to a newly designed DirectStream DAC (main board, and redesigned input board). And they have money, equipment, engineers, and - most importantly - schematics. Why would anyone try to do it now?

Again, it’s not a swappable PCB. Nobody will EVER design and manufacture a drop-in replacement. You have to resolder it on your own. But it’s rewarding, I promise you.

If I recall correctly (admittedly I may not), the PerfectWave power supply and case were kept in the DS DAC design so that PS Audio could offer an upgrade path to PerfectWave DAC owners via board swaps. The analog and digital boards followed the same back panel layout as the previous DAC for the same reason but I’ve never heard any indication that anybody other than Ted designed the circuitry on them.

Are there any microprocessors on the PSU board? I have assumed not, but if that’s wrong then I would have to agree with your hard scepticism. If there are no processors though I cannot understand your black and white “not swappable” stance. How hard is it to build a power supply and route some data signals between two ribbon connectors? I know it’s highly unlikely but surely it’s not inconceivable in principle?

Anyway, this isn’t an argument really and I’m not committed to “winning”. It’s been fun having my DAC grow in capability over the years and it’ll be a slightly sad day when I finally concede it’s reached its peak.

The PSU isn’t that big a big deal really IME. Ie, an external PSU wont transform a ~ stock DAC into a magic one. There’s too much other stuff corking it up.

I’ve tried JK’s trafos with the Vocm mod on a 100% stock DS Mk1 and it does make a quite nice result that many will be quite happy with IMO. Importantly I actually have tried it myself, not just yacking about it. I bought a used stocker and did only these mods to see what the actual sonic result would be. I’ve tried just about everything in fact. Is why I share many of the things I do. I’ve been through (4) DS mk1 by now. The ~ stocker is sitting here in a box; the DAC1 is playing here now. It needs the Studio upgrade and will get that as soon as I “finish up” (is it ever ?) with the power amp project. The existing Studio DAC is being enjoyed by my audio buddy. His previous unit, DAC2 was bought by another audio friend in DFW.

The stock regs to the analog output stage (OPS) aren’t bad. They can use some feed side beefing up IMO.

In the Studio DAC, which IS magic, we needed to create a new bi-polar PSU for the OPS. It uses a separate small linear PSU which I refer to as a “charging” supply, which is then down regulated via some standard linear regs, and then down regulated again to the actual OPS device rails via some very high performance discrete linear regs (eg, Sparkos). And there’s also some extra stuff required to stop the power on crowbar problem when you go to a bi-polar OPS PSU.

DAC1 here also has a bi-polar OPS PSU, but I just used a big brute “open loop” PSU on it. The hole open area in front of the main board is stuffed with large PSU caps. That big brute array is charged then by an SMPS with a very stout stage of LPF basically feeding the array. The power on crowbar issue is worked around by a simple delay scheme, 2 separate power switches which I can then manually delay and sequence. That was acceptable temporarily for my own proto use here. Its still working fine (as long as I don’t forget the sequence order lol :wink:

I’ll move DAC1 to full on Studio scheme soon including the PSU scheme. DAC1 also currently uses the TI diff amps in the modified stock type LPF scheme. DAC2 runs the same OPS, but it’s still just a beefed up stock regs uni-polar OPS PSU scheme. It sounds quite good, but not quite as nth degree transparent as DAC1 since it has to use DC blocking (of course with very high quality caps).

There’s nothing special about the small linear charging PSU in the Studio and pretty much anything will do in that regard, even an SMPS. I was going to reach for an SMPS for it in fact, but I already had the small linear sitting here in a box so went with it. There is essentially ~ nothing significant noise-wise that can make it through the 2 stages of regs to the output. However I also try to keep as low as possible output impedance for transients and such and tend to run somewhat larger, very high quality/wide BW output caps on the regs. AND the regs also need to be fed very well IMO, so I do similar on the inputs. It works for me. YMMV.