Modding the PS Audio Directstream DAC MK1 and MK2

Starting this Friday (11/15) we are giving customers 10% off  site wide until the end of November while supplies last.  This sale excludes VIP pricing upgrades.

Just a heads up.  We only have one complete unit available now and are down to a few transformers.  We won't be making any more till next year.

Here is the layout of components of our Limited Edition Signature Series PLUS units.

I use the Directstream mk1 in my headphone rig, so everything in this review applies to the APS “Level 1 upgrade” mk1, as it sounds when connected to my various headphone amps. Your experience using power amps and speakers might differ slightly, but the fundamentals should sound the same. 

 

About 3 months ago I finally got fed up with the harsh “digital glare” that all my newer delta sigma DACs seem to impart onto my favorite 1990s recordings. Even the latest ESS 9038 Pro flagship chip makes just about any 16bit/44.1 recording (from before 2010) sound thin, brittle, and abrasive. The latest Burr Brown chip is a little smoother on these 16bit tracks, but on 24bit tracks it sounds grainy and low-res compared to the latest ESS chips. 

 

I first tried going the tube amp route to help “warm up” these old 16/44.1 recordings. Unfortunately, all that did was accentuate the glare and add even more high frequency noise, even with expensive 1960s Amperex and RCA tubes. 

 

The only DAC I had which DID help strip away this digital glare was the original Chord Mojo. Unfortunately though, the Mojo has a lot of other shortcomings (e.g. resolution and soundstage) that disqualify it as an “end game” desktop DAC. Nevertheless, the old Mojo helped me realize that an FPGA approach is likely the superior DAC design path when it comes to playing back these older 16-bit recordings. 

 

The only problem? There was no way I could afford to drop $8k on even a USED Chord TT2+Mscaler (not to mention a DAVE).

 

So my search for a more affordable FPGA DAC eventually led me to the PS Audio Directstream mk1, which seemed like a really cool approach (i.e. switchable firmware “flavors”). I was delighted to find a certified used mk1 for $1500 online from The Music Room, so i went ahead and pulled the trigger. 

 

I won't say I was completely disappointed when I first plugged in the stock Directstream mk1, but I was definitely underwhelmed. My first impression, as a headphone listener, was just how intrusive the noise floor on a stock mk1 is. It's significantly noisier (on both low and high output gain) than pretty much any delta sigma DAC from the last 5 years, even cheap $300 DAC/amp portables. 

 

As far as secondary complaints about the stock DS mk1, there just wasn't much there in terms of dynamics, punch, or heft. Both balanced and unbalanced connections to my headphone amps were equally underwhelming in this respect. 

 

Despite all this, the one big thing my stock mk1 DID have going for it was in the resolution and timbre department, especially when running the latest Sunlight firmware. Even on a stock mk1, Sunlight serves up an impressive degree of smooth resolution that's miles ahead of what the original Chord Mojo is capable of. 

 

In fact, I'd put the DS mk1's FPGA in the same league as today's best ESS chip when it comes to pure resolution capability (a high compliment for a 12-year-old FPGA chip). The biggest strength of the stock DS mk1 is it sounds more naturally “syrup-y” and less thin/airy than ESS chips, despite its other aforementioned drawbacks.

 

This is where APS enters into the value equation. Thanks to the custom Rev2 Transformers+VOCM offering from Jeff and his son, I'm here to say that buying a PS Audio Directstream mk1 in 2025 is still totally relevant (and an exceptional value when compared to higher-end Chord gear).

 

After only a few weeks of owning a stock DS mk1, I decided the roughly $1250 “Level 1” upgrade from APS (Transformers+VOCM) was a must if I was ever gonna be satisfied keeping this DAC as the heart of my desktop headphone rig. Accordingly, I paid the $75 to ship my unit off to Jeff in Baltimore and kept my fingers crossed that this leap of faith would work out for the better. 

 

I'm pleased to report that it did, and Jeff turned my upgraded mk1 around in just 2-3 days time. I let the new mods burn in for 24-48 hours, then put my favorite analytical headphones on and sat down to give the modded mk1 a good listen through a neutral amp. 

 

The difference (with the rev2 nickel transformers and VOCM mod) was immediately noticeable over the stock mk1. Right off the bat I sensed a less intrusive noise floor, and therefore increased dynamic range, when compared to the stock mk1. Don't get me wrong, there's still a noticeable noise floor when I really crank up the volume on my otherwise whisper-quiet THX headphone amp (at least there still is with the $1250 Level 1 package), but that noise floor is significantly improved after the mods. 

 

The second thing i noticed was just how much more punchy and sure of itself the upgraded mk1 sounds compared to stock, all without ever sounding more compressed as a tradeoff. To the contrary, it actually sounds more open and dynamic after the APS mods. Harmonics now sound livelier and instruments richer, yet there's no added brightness or listening fatigue. There's also no added bass boost or anything like that, but the low end is definitely more solid while still sounding cleaner than before. 

 

Overall, the sound of the APS Level 1 upgraded mk1 is just more realistic and effortless than the stock mk1. It still sounds like the same great FPGA at the heart of the unit (because it is), but there's the sense when listening now that a veil has been lifted at its output stage, letting that near perfect resolution of the Sunlight firmware really shine through.

 

So if you're on the fence as to whether this type of $2900 “all in” approach is still worth it in 2025 (for what's essentially a 12-year-old FPGA DAC), I would say just look at the alternative. I've honestly never had the luxury to hear a Chord TT2 + Mscaler, but i would wager that the APS modded DS mk1 (even at just the basic Level 1 upgrade package) is in the same ballpark soundwise, and at a small fraction the price of higher-end Chord FPGA gear. 

 

For those who are curious, here's how I would describe the main difference in sound between the latest ESS flagship 9038 Pro chip and the Directstream mk1 (since I own both now and have done extensive A/B comparisons). With the ESS chip you will always hear the “air” around the notes of the instruments, whereas the Directstream seems to intentionally STRIP AWAY much of that air (without going TOO far or erasing the intended soundstage). All the impressive detail of the ESS is also present in the Directstream, but flipping back and forth between the two makes everything from the ESS sound a bit more like it was recorded inside a warehouse (in terms of added reverb). You don't really even notice this added air/glare until it's been stripped away by the FPGA inside the Directstream, but the result is a more pure sound of the instruments THEMSELVES, rather than hearing the room AROUND those instruments…if that makes sense. This is true for both the stock and modded versions of the mk1. The modded version just does it better.

 

Don't get me wrong. The ESS 9038 Pro chip is extremely detailed and spacious sounding, and it sounds amazingly good when playing back anything that was either A) recorded in the last 5-10 years, or B) re-issued in 24/96 or above. But where the ESS chips always seem to falter is with older recordings and 16/44.1 files like what you'd rip from your old CDs. In those situations there's a horrible “digital glare” and harsh treble edge from any ESS chip, and it makes your favorite recordings from the 1990s and early 2000s sound far worse than you remember them sounding back then. I do realize there's a nostalgia factor at play here too, but even still, this glare unmistakably exists.

 

NOTE: I ended up buying a Matrix X-Spdif 3 ($400 used from Apos) in order to feed the Directstream with isolated I2S signal, as opposed to noisy USB directly from my phone (running Qobuz). I also got a Chinese LPS off of AliExpress in order to better power the Matrix. There's no doubt a good LPS makes a difference here and i strongly recommend getting one if you go the DDC route. I even tried the $115 iPower X-Power power supply as a comparison, but the bigger/traditional LPS from AliExpress sounded even better, and it was actually a little cheaper too ($87).

 

One final thing: APS sells $99 “digital noise eliminator” shorting plugs to plug into the unused USB and 2nd I2S port. I'm not gonna outright say these are snake oil (because I've read threads here where several users report the benefits of shorting plugs on the mk1), but i WILL say that in my particular headphone setup I don't hear ANY difference at all with these plugs in or out. 

 

This little gripe aside, the custom APS rev2 80% nickel transformers really are THE BOMB and worth every penny. I mean, where else are you gonna find a transformer that's specifically designed for a PARTICULAR model of a particular piece of gear? Not to mention finding a service tech who has worked on literally DOZENS of Directstreams and can quickly identify any other quirks your old mk1 might have going on with it. 

Thanks for your review of our entry level modified DAC.  It is truly amazing what can be done with these MK1 Directstream DAC's.  Every step of our upgrade process shows great improvements.  Our top of the line Limited Edition Signature Series PLUS is just plain crazy over the top in sound quality.  Very realistic and dynamic. Simply amazing.  We have yet to find a DAC that can compete with it at any price point up to $20k.