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APS audio transformers

Custom audio transformers

We are no longer offering completed Signature Series or Signature Series PLUS DAC's however we can assist in obtaining a stock unit so we can perform the upgrades for you. We are only upgrading customer units at this time.  You send in your unit to be upgraded.


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Customer Reviews:




Back in August you upgraded my Directstream MK2 and I just wanted to let you know how appreciative I am for this upgrade. My system has had plenty of time to break in and I have to say it is sounding better and better still. Your upgrade was not subtle in my system. It sounded really good before, but now it sounds good beyond a level I was expecting. This year I added the BACCH for Mac to my system. Your upgraded DAC with the BACCH is magical. I’m even playing vinyl through the dac and my mind is blown. I know all this stuff continues to improve and develop, but I am feeling pretty satisfied right now and feel absolutely no need to change or upgrade anything. I really think your upgrade played a major part in all of this, so thank you from the bottom of my heart.


Happy New Year and I hope 2024 brings you happiness and a sense of accomplishment with a job well done.



Bob Kato


Feb 20

Awesome! When might the new board appear? I basically did all that by hand in my DAC#1 :wink: (plus more). And DAC#2, similar except still a 1 pole supply (but higher voltage, beefed up, etc).

BTW I am truly enjoying DAC#3 with your new trafos (thanks!) and just the VOCM mod. I have it direct connected to the amp(s) currently and loving it. Your trafos do sound marvelous. Nice work! I think a large capacity core does help (and of course high nickel as well).

Mar 4

Last night I installed the Nickel Beeswax transformers in my second DS Sr. They were delivered here in only 10 days. Well packed and double boxed. Just great! Thanks to @jkrichards!
After proper burn in I‘m curios how they compare to the Lundahls in DS #1. I will report later.

Mar 8

Loving the tantalum caps over R6 and nickel APS transformers after letting them get situated for a few days. I went with the non-beeswax transformers after discussing with Jeff. For reference, coming from Ted’s Sunlight, FARAD external power for analog, and XS4400s from a few years ago.

It was smile inducing right out of the gate. My intuition was similar to most other’s before me here. In general, the bass changed to a fuller and more musical form that closely resembles planar headphones (I’m driving Harbeth 40.2 AE). The delta feels more immediate, and I can see what all the hype has been about.

Though I didn’t measure a song before and after upgrades, it feels like I don’t need as much volume now. As a BHK pre owner, I like it to get to 53 to trigger that final click, which might mean lowering the DSD from 92. This will need to be played with and determined. I’ll adjust subs ever so slightly today.

Mar 8

Am on day one of burn in of the VOCM and APS transformers upgrade on the DS Mk1.

Agree the change in bass extension and slam is pretty significant. I have already had to tweak my dual sub setup bass levels and adjust the crossover levels with my monitors. Will probably keep tweaking them. My experience with burn in is the bass especially takes a few days to settle in and settle down and tighten up but there is no question there is a buttload more of it in mostly a good way.

Also agree on the overall gain level. It is significant increase at the same suggested 92 DS Mk1 level with my VAC preamp.

I did not take specific exact measurements, but the VAC preamp Vol dial is now at 8 o’clock for typical listening volume level (77-80db) and it was previously at around 9 o’ clock for the system to open up.

Will report more later.

Mar 10

Ok have about 50-60 hours of burn in on the DS Mk1 unit with the VOCM and APS Transformer modifications.
It is probably about where it is going to be at this point.
Bass was a little overwhelming the first 20-30 hours but has tightened up.

Short Review
There is simply more of everything

Longer Review version

More gain.
More extended and deeper bass.
More high end extension
More detail
More reverb trails
More space and air between instruments. No blurring of instruments.
More sound stage height, width, and depth
More control of the transients- no strain at all. It is effortless.
More quiet background
More inky black background
More natural presentation overall
More like live music on good recordings - suspends disbelief type thing.

It is really very nice. Highly recommend. I have been in this hobby for decades and I am sure there is better as there always is, and I don’t know what I don’t know, but this thing is a beast.
Very happy.

As an aside the service and turnaround by @jkrichards was excellent.

In a world where people drop stupid money on a power cord and sorbothane absorbers this is an absolute steal.

Easily equal to a major core component upgrade.

Mar 11

Very well said, @Lkdog !

So as promised some days ago I will briefly comment on my two DS Sr. for a comparison of the two most common mods.

DS#1 is equipped with:

    Lundahl LL1948 output transformers, parallel mode
    Nichicon ES Muse Caps (THT) 47 μF over R6
    Wima Film Caps 6.8 nF on C704

DS#2 is equipped with:

    APS Nickel beeswax transformers
    Vishay 220 µF tantalum caps (SMD) over R6

Both have some moderate 3M AB6005S shielding on relevant chips and are set to a fixed volume of 94. No other mods or differences exist at the time of comparing them.

So it is still some apples and oranges comparison because of the differences in the VOCM mod, but I am no professional reviewer. Just searching for my favourite DS for the next years to be happy with. And, guess what, I found it!

I will not repeat all the descriptions of the obvious benefits of these modifications. The topic is discussed over and over again. So here are just my subjective perceptions.

#1 gave a bigger „Wow“-moment right after plugging in some month ago. #2 was much more reluctant in the first hours. So a proper 200 hrs burn in was absolutely mandatory for #2, much more than for #1. Don‘t know if it were the transformers or the caps, it just took some longer time for #2 to settle.

The most appealing characteristics of #2 is the ease of its whole presentation. When #1 is sometimes a little too nitpicking especially in soundstaging, #2 keeps all instruments in a more natural order and size(!). The first vocabulary that came to mind was „coherence“. Everything has its place. And there is really a place for everything. No matter what kind of music or file type you play. So many details perfectly embedded in a realistic ambience, but never harsh or fatiguing. Just well tempered and balanced. Both perform better than I ever expected, but #2 is really always a little bit ahead of #1.

Sometimes I hear slight advantages for #2 also in terms of timbre, but here they are really, really close. Even a stock DS is absolutely my taste in this respect.

The even more realistic deep end of #2 is another obvious improvement. Don‘t know again if it is the caps or transformers, but texture and dimension of drums and bass is a little more on point on #2 as it is with #1. It is fast and never anemic. Just the right portion of good slam.

To sum up:

#1 sometimes shows some more unpolished, teenage manners, whereas #2 is more refined, mature and just more authentic. You know, I‘m exaggerating immensly.

For me, #2 is the way to go, no doubt. I really appreciate @jkrichards professional work and knowledge. So great!

Mar 11

I know everybody says this, but it does seem more valid now… My non HI Rez music is more enjoyable now. I may actually start to use my OPPO universal player more for redbook CDs again and stream lower rez recordings more.

Mar 15

I had @jkrichards install his new transformers and do the vcom mod at the same time. Already have his power board installed in my Mk1.

Going from the XS4400’s to the new transformers, I wasn’t expecting night and day difference, maybe slight improvement in details, a bit more space; basically incremental changes. Was I ever in a for a surprise!!! These transformers (and the vcom) made a very noticeable difference. MUCH more space, especially depth and extremely analog (not that the DSS is very “digital” sound to start with). I see NO reason to upgrade to the MK2 at this point. The upgrades already done to the Mk1 takes it to such high level that I’m not too certain that it could get much better. :slight_smile:

Mar 24

You will be incredibly happy with the end result! I had @jkrichards modify my DSS with the XS4400’s and I thought the result was spectacular. Sent it back and had him upgrade it with his APS transformers and do the vcom mod and I’m blown away how big of a difference that made! I can’t see any reason to upgrade to the DSS2 any time soon

Mar 27

You will be gobsmacked! I’m so pleased that jkrichards has developed and made available these upgrades which IMHO are truly world-class! (he did my mods)


Mar 31

My DSD MK1 is back from having APS transformers , VOCM mod and APS external power board fitted
WOW , anyone thinking about going down this path I highly recommend it .
Its only got a fews hours run-in on it but I can already hear how deeper , tighter and faster the Bass is .
The sibilance that I heard on some songs is gone . I have a wall of sound .
A big thanks to @jkrichards for making the parts available ,@tedsmith for all his contributions on this forum and of course to all the other people who have contributed to the mods .

While the top was off I noticed that one of the heat sinks seems to have discoloured compared to the other 3 next to it . It seems to run hotter than the others so I guess that may be the cause . Is this something of concern .

Apr 3

So… I am in the fortunate position to be able to compare a bone-stock MK1 vs a jkrichards modded MK1 (Transformers + VOCM). I purchased the latter from jkrichards, which he had already modified.

For the tests, both DACs were left on for 2 hours for some warm up. Both powered from a PS Audio P3 generator. RCA outputs to 2 inputs on the preamp. Both fed from an Innuos Zen3 mini via coax (which I had to swap between the DACs for testing). Before getting into listening, I used a dB meter and pink noise to mark on the preamp the volume settings as the modded DAC has a bit more gain and I didn’t want that interfering my impressions. I also decided that using the pre was better then attenuating the output on the DAC; the Preamp we make here uses a TVC so it is very consistent across the volume range.

Usually comparing components, the difference in character immediately makes certain things stand out and may throw off more objective listening and critique. It’s not the case here because the character, tonal balance is almost the same. The “house sound” is pretty similar… so if you like the PS Audio DAC sonic signature, you won’t be thrown in a different direction here.

So… the sound. It is just simply, consistently, better. The separation in the mix of instruments and voices is improved. Definitely a bit more prat. Sightly more airy without being turned up. As others have mentioned, the bass is definitely improved in terms of control and tonality (I personally find real tone in bass difficult to achieve and this mod delivers the goods) The whole sound is more refined, more controlled, without getting dry or astringent… nor did it get lush and colored in the process.

Definitely a worthy upgrade and really a no-brainer if you like your Directstream but want more of that same goodness. It’s a Directstream living its best life… as the kids say.

Now to pack this puppy up for AXPONA.

Apr 12

OK, I think I have the whole enchilada going now.

APS Nickel transformers
VOCM mod
USB shorting plug
HDMI shorting plug
Have an aftermarket fuse.

Just picked up a used @jkrichards External power controller board from a fellow forum member and I installed it tonight.(Installed easily and well designed).
Got a Zerozone external LPS. (Build quality looks great by the way)
Made up the correct umbilical cord cable termination ends.

It all powers up as it should. LOL.
I can’t listen to music as everybody is asleep right now.

The APS transformers/VOCM mod upgrade is well described. It is killer. Have had that burning in off and on a couple weeks now.

Stupid question- what exactly does the External LPS for the DSD analog board do for overall sound in people’s experience?

Will be able to listen tomorrow.:rofl:

Apr 12

Well, have it fired up this morning and it all works flawlessly.
As for the sound- it was already excellent.

The black background and purity of sound is ridiculous.
Overall the control that this modded DAC has over whatever source material you feed it is really impressive.
It never strains.

Thanks to all for the creativity in figuring out all of these mods over the past couple years to an already very good DAC.

Apr 18

Finally got my DAC back from the technician with XS4400 transformers upgraded to APS, all R5 and R6 replaced with thin film equivalents and R6 paralleled with an extra 47uF to stabilise Vocm. While I’m sure there’s going to be some burn-in time before it settles in there are some immediately discernible improvements.

The DAC volume control remains fixed at 92 like it was before. With the transformer change the output level is higher so I have to use different positions on the pre-amp’s potentiometer volume control to get the same volume. I don’t think that impacts these observations though.

First, the noise floor is obviously lower. In the opening verse of Dire Straits’ song Brothers in Arms, there is an almost-muted high hat gently marking selected off-beats. I think I discovered this via headphone listening some years prior to getting this DAC and the DS has always struggled to extract that detail through my speakers. Not any more, it’s plain as day once you turn the volume up high enough.

There’s a similar story in the bass but it comes across as grip and control rather than “detail” or a lower noise floor. In the silent bar right before the 2 minute mark in Angus and Julia Stone’s Yellow Brick Road, there’s a very low level kick drum pacing out beats 2, 3, 4. This is another detail I haven’t heard from my system in years but here it is just like I recall having discovered on some other setup I can’t recall.

But the bass overall is just so much better. It isn’t louder but it’s stronger and deeper and better timed. The pulsing bass in Jewel’s What’s Simple Is True is finally rhythmic. Groove Armada’s Suntoucher drops into the abyss but no longer disappears. Piano Black on the first disc of the Cowboy Beebop OST now has clear bass notes on every beat of every bar instead of just most of them.

Along with the extension and timing comes more harmonic structure down low, like in dense piano chords. And plucked double-basses have never had so much presence in the room – feel the air compress around you when the bassist aggressively mutes their instrument on the 2nd count of every 4 in Umi Yushida’s version of This Masquerade.

Thanks yet again to Ted, and JKRichards and son for the chance to enjoy continued improvement on this DAC over such a long period. This should keep me satisfied for a few years until a MkII with APS transformers eventually seduces me.


2 posts
08-14-2023 at 11:22am 

For those who own MK1, the APS/VOCM mod is really a better bang for the buck.  Comparing the unmodified MKII with the modded MK1, I can concur that the latter sounded better than the former.  The MK1 although is getting old, is a mature product with a pretty stable firmware.  

43 posts
05-21-2023 at 02:46pm 

This DAC upgrade is insanely good. I initially let it burn-in  non-stop via the USB stick on the PST, for 200 hrs, but the sound has continued to improve under normal use.

The soundstage is rock solid with vocals and instruments clearly defined and focused.  The soundstage has also expanded in all directions, creating more separation and air around the performers. And the bass, OMG the bass, is crazy good. Tight, punchy, and incredibly rhythmic. 

This is a component level upgrade, without the price tag. 


straightwire Regular
July 18

I’ve been cooking Jeff’s nickel transformers for about two weeks in my MK2 and now and they seem to be settled in. Jeff was kind enough to scrape together enough nickel plates between father and son and get a pair assembled prior to his overdue shipment. I had Jeff do the install, and it came back in quick fashion with an AP performance plot as well.
As for the sound, I can easily say it is another veil lifted in my system. There is no fanfare, or chasing of the vagaries like in an expensive fuse. This mod stays true to the script. It doesn’t change the character of the MK2, it enhances it. Thinks are a little quieter, and at the same time more dynamic. I have set my preamp one notch lower, yet perceive the same volume. Bass is a tad tighter and deeper as well. What it did for imaging was the biggest “wow” in my system. Instruments are more in focus, in a more defined space.
So, I like the APS transformers and feel the hassle and expense more than justified. It’s another step closer to making digital sound, well, less “digital”. If you make the plunge, be sure to put 200 hrs. plus on them to smooth them out.


43 posts
04-27-2023 at 11:08am 

Placed the newly upgraded PS Audio DSD MKI DAC, which I sent to JK Richards to do the mods, into my system at around 6 pm yesterday evening after the system had been unplugged for two weeks and was pleasantly surprised how good the music flowing from it sounded. Normally my system remains turned on and in standby at all times, but even then, it takes at least 30 minutes to an hour of playing music before the sound really starts to gel to the point where I get lost in the music. Yesterday I was held captive immediately and remained affixed in my listening chair for 4 hours straight as I went through my music collection as if hearing these silver discs for the first time. The PS Audio MKI DAC was no slouch to start with, and I thoroughly enjoyed listening to music through it, but it’s an entirely new and more refined DAC now.


The top end is more detailed while also sounding smoother and more delicate. Cymbals have more shimmer and sparkle, and their presence lingers longer as the sound decays into a blacker background. The midrange and vocals sound absolutely stunning and to die for! Again the lower noise floor reveals subtle inflections in the vocals that were previously obscured, further suspending my disbelief.


The bass now digs deeper and is more controlled and articulate. The foundation of the music has more drive and bass lines are easy to follow now. I also noticed I don’t need to listen as loud in order to get the bass to come alive and really boogie. Before when listening at lower levels the bass never really had the presence and punch it did when turned up louder. Now even at much lower levels everything including the bass sounds prefectly balanced.


I can say without hesitation, this is the best bang for the buck upgrade I’ve ever made.


417 posts
04-27-2023 at 11:14am 

Agree with above post as it is almost exactly how I would describe the upgrade. I can attest to the massive enhancement of the DSD Mk1 after the APS transformers, VOCM mod, and I2s input shorting plug on unused input.

I had @richardselectronics do the work on the unit. Quick turnaround.

Huge soundstage, and control with detail and presence.

The Bass response is deep and defined.

If you have a DSD1, this is a no brainer. It is then an endgame DAC.

I have had a lot of separate DACs and high end source units with modded DACs from a lot of the usual vendors here in last 20 years.

All good, but this is another level totally for the price people blow on cables here.




Just received and installed JK Richards’ most excellent APS nickel core audio transformers in the Mk1 DAC. Very initial impressions are extremely positive. Have listened to two very familiar Lyle Lovett cuts so more to come later today and this weekend, but I’m really liking what I hear so far.

Also, @jkrichards tip to buy some kind of proper de-soldering station is brilliant. It took me about 5 minutes to remove both Edcor XS4400 transformers and another 10 minutes to solder in the new APS units. DAC powered right up and worked the first time. Yay!


APS DAC Xformers



Update: Thanks to JK Richards for pointing out the need for the Vocm upgrade as part of the nickel transformer swap. Bought a magnifying lamp and discovered I can still handle surface mount parts without too much fuss.

Just finished this and playing some more classic Lyle Lovett. Man this DAC is getting absurdly great.



Yessir. The sound is simply magnificent. Hard to describe the combination of both ease and articulation. Back to that proper place of just enjoying loads of music. A good sign for sure.

My audiophile goal in general is to elevate both my digital and analog front ends to be equal but different. So far so great.




Just received my DAC after the Vocm and APS xformer mod. Read the reviews on this thread and expected an improvement; however, I’ve heard it before and am a tad jaded. I expected a subtle improvement. Whenever, I make a change the first things I put on is the Stereophile Vol 2 Test Cd to verify I didn’t swap channels and phase. As I listen to “The Fender Bass Guitar you are about to hear should appear to come from the left……”, I’m like OMG! The low end authority and inner detail was so obvious. The out of phase test throws an image to the front and right of the right speaker for some reason. This time it is farther forward and to the right and chiseled in granite. Wow, this is really good. A few folks mentioned more bass. I was a tad concerned as it occurred that the software may have been tweaked to make up for the original xformers and with the APG xformers it may be an issue. I thought not a biggie as I can correct. Well after only sitting with this for an hour not on board with the more bass statements. Authority, control, articulation of the low end; yes, absolutely concur, but not larger amplitude. When I get around to doing Room EQ Wizard (REW) sweeps I do not expect to see more bass. So freaking happy. To put this in perspective, IMO this was a bigger upgrade by a wide margin than when I went from Perfectwave MK2 to the DS DAC (aside from going from edge to buttery smooth) from a perspective of detail, soundstage, chiseling of instuments within soundstage, tight grip on low end. Really happy. Thanks Jeff!


43 posts
05-14-2023 at 03:36pm 

Can't give you a break down of the percentages of each mod, as I had Jeff install both mods for me. But I would estimate the percentage of both mods combined is easily a 50% improvement, but in terms of musical involvement and enjoyment, there's a night and day difference. Every parameter of the sound has improved. Considering the cost of the upgrades, even if you pay Jeff or someone else to install the mods, is a no brainer. 


MK2 Reviews


straightwire Regular
July 18

I’ve been cooking Jeff’s nickel transformers for about two weeks in my MK2 and now and they seem to be settled in. Jeff was kind enough to scrape together enough nickel plates between father and son and get a pair assembled prior to his overdue shipment. I had Jeff do the install, and it came back in quick fashion with an AP performance plot as well.
As for the sound, I can easily say it is another veil lifted in my system. There is no fanfare, or chasing of the vagaries like in an expensive fuse. This mod stays true to the script. It doesn’t change the character of the MK2, it enhances it. Thinks are a little quieter, and at the same time more dynamic. I have set my preamp one notch lower, yet perceive the same volume. Bass is a tad tighter and deeper as well. What it did for imaging was the biggest “wow” in my system. Instruments are more in focus, in a more defined space.
So, I like the APS transformers and feel the hassle and expense more than justified. It’s another step closer to making digital sound, well, less “digital”. If you make the plunge, be sure to put 200 hrs. plus on them to smooth them out.



Feb 7

Last Thursday (05/Feb/23), I received my DS-1 from Jeff & Son with a Vocm upgrade and the new PSA Beeswax Transformers installed. Unfortunately, it took a lot longer than I thought to give it a listen and report.
My DS had the SX4400 upgraded transformers plus the LPS with Jeff’s card for a year, with no other internal updates. This new transformer upgrade came at a great time as I haven’t changed my system in about a month. I sent my DS to Jeff because I don’t do internal projects (except fuses), so because the Vocm upgrade was essential to the APS upgrade I made Jeff do the work. I’m really thankful I did because Jeff and son found that I had a DC offset problem which they fixed for me.
So, I get my DS back, get it all set up in it’s spot on my shelve rack, power up my equipment, pressed PLAY, and, nothing. Turned out my primary McIntosh C-20 preamp decided this would be a good time to develop a problem. All lit up but no sound.
It took a while to figure out what was wrong and get the preamp out and deal with it. Luckily, I have a Quad system and I use two C-20s (one in front of the front channel amp and one in front of the rear channel amp). Normally I review new additions and upgrades just using stereo playback – not quad playback. So, I took the rear channel C-20 and moved it into the primary spot and slowly moved forward toward my listening. I mention all this because there is a reason the one C-20 is used as the primary. I’ve always felt my primary C-20 had a little edge in sound quality, although both preamps have been extensively upgraded and improved. Nevertheless, my primary C-20 might have performed a little better as I listened to Jeff’s work.
And, My-O-My what great work this is turning out to be.
Unfortunately since my DS didn’t have the Vocm upgrade this review will have to cover both upgrades at the same time. When I finally got everything all plugged in and ready to go, there was only about two hours burn in time on the new parts. Initially there was a bit of roughness to the overall sound but I had to do a lot of fine tuning to my adjusted equipment lineup before I could make any kind of judgment. I don’t know if the initial roughness was in part due to lack of burn in time, but if it happens to you don’t worry about it.
I came back two days later when my DS had about 50 hours burn in time and there was a sizable improvement in sound quality. I made a couple more adjustments to my equipment and all of a sudden my system just BLOOMED, (kinda like when the Wizard of Oz went from black and white to color). The major thing I noticed was that the instruments were now totally separated from each other almost like pinpoint stars in the sky. Because of this the background seemed blacker, but I think it was the fantastic separation that caused me to notice the background more. All of the instruments had definite positions on the soundstage and all were locked in. Up till now I always had a little bit of uncertainty in the soundstage spacing, but now any vagueness is totally removed.
Because the instruments are so distinctly located on the soundstage, more detail is available than I’ve ever had. There were some points in music I’m very familiar with, that I heard textures and tonalities I hadn’t heard before. I was listening to Annie Lennox sing and I heard her do a couple of subtle phrasings with her voice that I had never been able to notice before. The interesting thing here is while instruments seem to be locked into their own individual spaces, massed vocals still seem to be linked to each other. Background vocalists still sounded like a collective unit, rather than a number of individual voices. Personally, I like that
Likewise there were parts played by musical instruments that were clearer and more defined and yet the tonality improved and the warmth was maintained. Another song, this time by k d lang, called “Wash me clean”, presents a big challenge for musical systems due to an acoustic guitar playing arpeggiated chords while the bass pedals the dominant note of the guitar chords. Quite often when the bass and the guitar strike the first note the guitar notes simply wash out until about the third or fourth note. This time however both the base and the guitar were separate and you could follow the guitar all the way through while the bass held the note. Very impressive
A word on the bass response. The upgrade makes the bass much more noticeable than I previously had. Matter of fact, I had so much bass that I immediately turned down the bass on my system, so if any of you don’t have enough bass this may help you.
For me I’m calling this a big win, and this is just with 50 hours on the machine using a different preamp than I was used to. So, to sum it up I think the biggest gains here are:
• The definite locking down of the spatial positioning of different instruments.
• Added clarity of and the dark space around the individual notes and voicings.
• Better tonality and sound quality of instruments.
• The added detail actually helps reduce any harshness or raspy quality, especially in vocals.
• Better, more authentic, more distinct sounding bass – although at a louder volume.
Unfortunately I can’t tell you how much of the improvement that I heard is due to the Vocm upgrade or Jeff’s ASP transformer upgrade. I can tell you the upgrade seems to be well worth it. Right now, both my C-20s are in the shop so I won’t be able to really sit down with my new DS for about another week or so. The DS is idling and I might even run some music through it from time to time, so that when I get everything back in line it should have close to 200 hours on it.
I’m thinking that’s going to be a really good day.



Hi Jeff,


The DAC arrived and I just connected the DAC. Everything checked out - I was little worried about the PSA packaging.


Wow, I am impressed by the SQ. I didn’t like XS4400 for several days but within a few minutes I can tell the APS transformers/VOCM mod are in an entire different league. I expect it to get better with some hours on it. 


You and your son are making this hobby of Hifi more fun! Many thanks.


Best wishes,




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. 


Just a quick note to mention that my fully-modded Mk 1 just seems to get better and better.....  Honestly, I fire up the system with the intention of listening to vinyl and after warming up on streaming files (Roon ROCK NUC, Allo DigiOne Pi) I am quite literally floored by the sound quality.

It is superb in all aspects, so much so that I really find it hard to fathom that the stock MK2 would even equal it.  I'm really glad I got the mods done when I did!  to quote GME109 from a previous post "It transformed a decent DAC into a total beast. The value proposition is off the charts. "  I couldn't agree more.

I got tired of waiting for the AirLens and didn't make the beta cut, so I'm happy I didn't pull the trigger on one of those as well.

Thanks again @jk_richards 



To me the APS transformer upgrade is a worthy mod since the sonic improvement was quite nice after I have it installed. After the Massive update the MK2 is sounding incredible. I now think the initial “warmer” bottom was just a normal break-in process because now the unit is barely warm. In fact, the stock unit ran quite warm at beginning too as I remembered.

I have not experienced any problem with my MK2 so far, and with the “normal” temperature now I expect it will serve me for a long time🕺🏻




02-12-2024 at 11:08pm 

Just wanted to post my limited experience with the APS transformers in the MKII. I’ve only had them playing 48 hours or so. I don’t know Jeff other than dealing with him through the purchase and install of the transformers, but what he and his son have created are a revelation. I have only dreamed of sound this good. The reference tracks I use have never sounded anything like this, even in more expensive systems. the purity of sound, the intimacy of vocals, the realism, staging and separation are abundant in spades. My system, being beryllium for mids and tweeters, along with an electrostatic super tweeter, can be brutal, letting you hear every shortcoming with sources. The APS transformer upgrade, in my system I think is bigger than an amp or preamp upgrade. As can be seen from the response curves Jeff posted, yes the treble is more extended and crystalline than the stock Edcore units. Buzzy brass from the Athena Rachmaninoff Symphonic dances sounded much more like real horns and less buzzy mess. I could hear much more of Bill Evans hands doing different things and get a much better sense of the piano’s soundboard in general. Right now I’m not using a preamp, so I’m only playing my DSMKII between 40 and 70, so when I finally put a preamp back in the system, I may hear even more goodness. I’m not running Massive firmware yet, as I didn’t want to change too many variable at once, but it will be interesting to hear if I like Massive more than Antero. I do hope Jeff decides to offer the MKII transformers again some day, as I’m trying to convince a friend with a MKII he needs to do this upgrade.




My friend, Dave has finally got the 400 hours on my Mk2 and around 300 hours on the Mk1.  I've only had it for two days, but the modded Mk2 is amazing ... it allows the emotions of the music to affect you a good amount more than the stock Mk2.  The sound is so much more "organic" ... more like listening to the musicians and their instruments rather than a high quality recording.  Truly amazing and rewarding ... you just don't want to stop listening.  It definitely is addictive ... but in a good way!   





Hi Jeff

Just emailing to let you know how impressed I am with initial listening to mods.

Realizing it will only get better, my initial impression is a much clearer picture into the music. Less background noise, more slam, and soundstage improvement with more air around instruments and voices that make listening a more enjoyable experience. 

Did have a question on fixed volume of 92. I assume this is the sweet spot on volume and mods required change to fixed volume vs prior ability to change volume settings

Thanks again





We had fun yesterday comparing my Signature Series Plus with my friends modified Directstream.
He had his DAC upgraded last year by APS with the standard VOCM mod, the original APS nickel transformers and some power supply mods. Both units have Snowmass V1 (3.00) firmware installed (The APS recommended firmware)
We started off listening to his DAC. We switched all the cables from mine to his and set the DAC’s volume to 92. It sounded really good although I could hear the deficiencies in comparison to what I was used to hearing however I didn’t say anything. We both listened to his favorite tracks. I picked a couple of my favorites then we switched in my DAC. The first few seconds they sound very similar however after about a minute he looks at me and states I wish mine would sound so real. It was so obvious after a few minutes of play the difference was so big, its chameleon like, mood-lifting performance and energy gains were…so real sounding. You need to hear to believe it how it handles double drums, fast solos, percussive instruments and quick shifts in dynamics. Nothing will slip past its gaze like it knows exactly what it will be playing. With the Signature Series Plus, expect an unlimited well of explosive dynamics and that’s how we both felt it was with every musical genre. It was rich sounding, full-bodied, but also very defined, preserving sharp leading edges. You could hear the room it was recorded in so clearly. Detail retrieval or transparency are redundant with a unit like this, as it will playback every single bit of information with utmost accuracy and in a very life-like manner. It doesn’t sound like digital, it sounds like music played back in real time, by real musicians sitting in front of you, playing just for you. When it comes to resolution and dynamic range, My DAC single handedly outperformed his DAC.
Don’t get me wrong his DAC sounded wonderful just not as good as the Signature Series Plus.
Before he left last night my friend ordered the Signature Series Plus upgrade at the VIP price and never looked back.


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