Audiophile Style Community Review

Reality Quest: Power and Digital Audio with the Sean Jacobs DC4 and Sound Application PGI TT-7 (Part 2 of 2)

Sean Jacobs DC4 and Sound Application PGI TT-7

In Part 1 of this review, I shared the transformational impact of the Sean Jacobs DC3 and DC4 power supplies with a Chord DAVE DAC. In Part 2, I shift my focus from the DC side of power to the AC side of power, reviewing the remarkable Sound Application Power Grid Interface TT-7 power line conditioner.

Background on Clean AC Power

So far, this review has been focused on DC supplies and the impact that they can have on a DAC. So what happens when you go upstream to the AC side of the chain?

As I mentioned earlier, a couple years ago I upgraded my home electrical wiring and heard a surprisingly significant improvement in dynamics and soundstage (especially depth) and reduction in the noise floor for my system. 

Starting at my electrical panel, my audio AC power baseline is the following:

  • Two dedicated 30A circuits (10-2 Romex wiring in the walls), each connected to an upgraded high conductivity outlet, dedicated only to audio equipment. The line length from my electrical panel to these outlets is ~15′, so extremely close proximity to my home electrical panel.
  • A dedicated Topaz Ultra Isolation Transformer (model 91018-31T). This is a 1.8KVA model, with ultra low capacitance. I have my isolation transformer wired for balanced power output.
  • A variety of upgraded power cords, ranging from a Pangea AC-14SE to an Elrod Power Systems EPS-3 Signature to my reference Sablon Audio King power cord with the beastly Bocchino connectors.
  • Synergistic Research Orange fuses for both my Sean Jacobs DC3 power supply and Taiko Audio SGM Extreme.

Each of these resulted in notable step up in dynamics, bass resolution, and spatial imaging, with a reduction in the noise floor (for me, reflected in how relaxed and natural and stress free a presentation is). In Part 4 of my Taiko Audio SGM Extreme review, I detailed the impact of each of these additions in my system, but clearly, the cleaner and faster the power, the better everything becomes.

So is there more that be done to optimize the AC side of the chain? To me, the answer has clearly been yes:

  • While the Topaz isolation transformer was a godsend to send the noise floor of my system to a deep black, it also dulls dynamics on dynamics beasts like the Extreme (I needed to bypass the isolation transformer and go directly to the wall to get maximum sound quality from my Extreme). 
  • Even with all these other power optimizations in place, the SR Orange fuse still took dynamics up and noise down, so something was still getting through to both my DC3 (then DAVE DAC) and my Extreme. 
  • The astonishing impact of the Sablon Audio Prince (and later, King) power cord direct from the wall outlet to my Extreme also highlighted the opportunity that was still there to do better on AC power delivery.

But how best to do better on AC power? With the seal broken on evaluating power optimizations, it was time to return to the AC side of my audio chain as well. 

As I looked at options, I researched power regenerators (dirty power in, which runs an electrical generator, generator then generates clean power out to your devices), large battery banks (batteries charged with dirty power, batteries then run an electrical generator to create clean AC power out to your devices), and power line conditioners (dirty power in, PLC filters gunk out and conditions power, and clean power out to your devices).

Going back to my goals for AC power (minimal noise, including RF noise, and ability to instantly respond to dynamics current loads), I was able to quickly narrow the decision tree. 

Power regenerators have huge appeal for cleaning up gunk on the line, but I was leery whether a generator that is reasonably sized would be able to have the dynamic current reserves to react to aggressive power transients. Best case, because of internal inefficiencies, a generator would still be well short of dynamic current capacity of what was coming from the wall. In addition, I’d be at the mercy of whatever process the manufacturer chose to use to create the AC waveform (the generator itself could potentially be a source of digital noise).

My experience with batteries for DC supplies was decidedly mixed, so I was leery of dropping them on the AC side of the chain. Batteries are awesome for mains isolation, but discouragingly slow in keeping up with transient current demands (the chemical reactions in batteries can only go so fast). On the AC side, battery-based solutions have similar challenges as power regenerators: by using DC on batteries to power an electrical generator going back to AC again put me at the mercy of the dynamic current capacity of the AC power generator in the battery bank. Without a closet sized unit with massive parallel battery cells and a huge generator, I did not see a path for a battery-based power conditioner to be able to keep up with the speed of a direct wall power connection. 

That left power line conditioners – AC in from the wall, lots of filters to reject everything other than 60Hz, all while being as electrically invisible and neutral as possible (that is, as low an impedance as possible, mainly capacitance and inductance). In an ideal world, all power gunk is rejected, and the conditioner electrically appears like a straight ultra heavy gauge wire between the electrical outlet on the wall and devices on the other side. 

But how to keep AC clean, while keeping the AC output “wall-outlet-level” fast? 

Many of us have had the experience of plugging power amps into surge protectors or power conditioners of various types, being disappointed by their sluggish response, and going back to plugging them directly into the wall. Anything between a device and the wall slows down devices that have big swings in power demands. (Remember, one of the main reasons Class A amplifiers sound so incredible is that they are always consuming a constant amount of power, even when nothing is playing…incredible for your ears, horrible for your electric bill). 

Whatever the strategy, introducing filters/batteries/generators in order to clean power directly competes (electrically) with being able to deliver power as fast (dynamic load) as being connected directly to the wall. On some components, the benefit of cleaner power outweighs the detriment of slower power. For other components (like amps and dynamics-monsters like the Extreme), the benefit of faster power by going direct to the wall outweighs the detrimental impact of having dirtier power. 

The art of power conditioning has always been finding the right balance between clean/slow power and noisy/fast power for each component in your system, in order to get the maximum performance out of your system as a whole. 

But is it possible to have both clean power and “wall-outlet-fast” power at the same time?

It turns out that for years, a surprising number of ears that I trust (and have a similar listening affinity to transient timing and dynamics as I do) have been urging me to audition one of Jim Weil’s Sound Application power line conditioners. Surprisingly, they have urged me to do so not just for smaller components, but also for demanding components like power amplifiers. This certainly got my attention.

Jim Weil has spent the better part of the last three decades systematically and meticulously attacking the challenge of delivering both clean power and dynamic fast power at the same time. According to these trusted ears, Jim had something very special with his PLCs, that I needed to hear one in my system.

Despite all that patient cajoling, I had steadfastly resisted auditioning PLCs for the last several years, not because I did not believe it would have an impact in my system, but rather because I wanted to first be sure that I had the rest of my systemed tuned to where I wanted it to be. The best power conditioning should be absolutely neutral and invisible, but they can also impart their own sonic flavor and signature. I did not want to lean into PLC to compensate for or mask other issues in my system, so I practiced strict denial as I was working through the rest of my system. 

Now, as my Reality Quest is approaching the end of its Zeno’xian arc, the time had finally come to see what power line conditioning could do for me.

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Enter the Sound Application PGI TT-7 Power Line Conditioner

Jim is currently offering three different versions of his flagship TT-7 power line conditioners: the Reference TT-7, a 120V version of the Power Grid Interface (PGI) TT-7, and a 240V PGI TT-7 (which also works with the US 120V power grid). These range from $10,000 to $20,000, so a significant investment (to say the least). Each is hand assembled and tuned by Jim to his very exacting standards, and he is relentless in looking for new ways to make them better.

Jim has rapidly evolved his products over the years (and it is not always easy to track down information on them) so I asked Jim to share some background on his latest offerings:

“Sound Application is a United States manufacturer of ultra-performance power distribution equipment. We have been designing and building our power line conditioners for over 3 decades. Sound Application design philosophy can be summed up in one word: “simplicity.” Our designs are meticulously hand-built, and pared down to the absolute minimum resulting in ultra-low impedance producing maximum sonic speed and transient response and yielding a level of transparency and resolution that is unrivaled. 
Our methods have been validated through measurements and audio testing. Where possible, cold welding is performed in lieu of soldering to maintain sonic purity. Enclosed in our signature monocoque chassis, the newest SA models incorporate the finest components including custom Rel TFT capacitors, Virgin Teflon, G5 Titanium hardware and Acrolink 99.99999% (7N) pure copper 10 gauge power wire. 
Transverse Mode (TM) noise occurs only on the “Hot” in relationship to the “Neutral.”
Common Mode (CM) noise is “in phase” noise present on both the “Hot” and “Neutral.” 
After years measuring the US AC mains, I came to the conclusion that the dominant form of AC noise on the North American power grid is Transverse Mode. The SA 120v PGI TT-7 is a Transverse Mode filter with bandwidth of 2.6GHz. The SA 120v PGI is a purely capacitive filter, with every capacitor aimed at a measured noise band. Of the total capacitance 95% is created with custom Rel TFT capacitors, presenting a total capacitance of less than 0.5 µF including massive spike and surge protection. The 120v PGI is specifically designed for poor power situations coupled with high current demands. The amazing performance of this device improves at higher current loads. 
The SA 240v PGI TT-7 is a completely new design and is the fastest and quietest design that I have built.  While intended initially for the 240v circuits of Europe, Australia, and Asia, this device is also suitable for 100-120v circuits. The SA 240v PGI has both outstanding TM and CM noise reduction to over a gigahertz bandwidth and becomes purely Transverse out to 2.6GHz. Having employed amplifiers of various topologies up to 2500 watts per channel, thus far all of these amplifiers have exhibited higher performance with the SA PGI in series vs what the power company delivers to your home.”

That’s a lot to get my head around, but how does it sound? All 10+ people that had independently recommended the TT-7 to me had told me some variant on “Do not listen to one unless you are willing and able to purchase one”. 

I will pass this same admonition on to you – once you hear what the TT-7 is able to do for all the components in your system, there is no going back.

(By way of disclosure, I have happily purchased the TT-7 reviewed here, with no financial consideration or benefit from this review)


For this review, I listened to both the 120V PGI TT-7 and 240V PGI TT-7. Both share a common tuned resonant aluminum alloy enclosure design, using a welded two piece stressed skin design. However, the internal filter circuit topology is different between the two, giving each a different characteristic impact on sound, and each being more suitable for different power situations. 

The Reference TT-7 and the 120V PGI TT-7 share a 19-stage step-ladder capacitive (SLC) filter design, with the 120V PGI TT-7 being fitted with upgraded components versus the Reference TT-7. These devices are best for more challenging power situations where massive voltage spike and surge protection may be needed, or with some very specific kinds of equipment that because of their design are more susceptible to lower frequency noise (Jim can advise here).

The 240V PGI TT-7 uses a modified unbalanced CLC topology, with an order of magnitude lower capacitance than its SLC brethren. While having slightly less protection than the SLC units, it has a more refined sound and is much faster.

Both units are built with the finest materials and components available, including custom built virgin teflon TFT capacitors (designed specifically for Jim by Bas Lim, founder of Reliable Capacitors, which is now part of Wilson Audio), a custom ultra low resistance CarlingSwitch magnetic circuit breaker, G5 Titanium at critical junction points, highest purity 7N 10 gauge Acrolink wire for internal wiring, and carefully selected materials at interfaces to minimize parasitic capacitance.

Jim takes special pride in both material choices and assembly, and has developed a variety of refined techniques to cold weld components and tune the assembly to maximize noise rejection, all while minimizing impedance to virtually nothing. As an example of the meticulous attention to detail, each unit is tuned on the bench over the course of four days to minimize the impact of vibrational nodes, and better reject troublesome frequencies (like the ubiquitous 2.4GHz band).

noise diagram

At its core, the TT-7 is basically a buffer between your home and neighborhood power grid and your devices, eliminating electrical noise and protecting your equipment from spikes and surges.

The TT-7 filters out electrical noise from the AC line, both common-mode noise, which is in phase noise between hot/neutral and ground, and transverse-mode noise (also known as normal-mode noise), which is noise between hot and neutral. It also does power factor correction to optimally deliver power to downstream devices. 

Unlike many power line conditioners the TT-7 filters noise across an extraordinarily high bandwidth, filtering transverse-mode noise up into the 2.6GHz range (and I have learned all too well how RF in the 2-2.5GHz range disrupts soundstage and timing detail on the Chord DAVE…keep your WiFi base stations and microwave ovens away from your DAC!). 

The TT-7 is also about not slowing the transient response between current demand from your devices, and allowing your wall outlet to deliver instantaneous current to your devices as quickly as it can. Amazingly, even with wide bandwidth aggressive filtering, the PGI TT-7 presents a capacitance in the sub micro Farad range, implying lightning fast speed and dynamics. 

Jim has been able to achieve this through meticulous attention to components, interface and connecting materials and wires, and careful attention to every weld and screw. The net result of all these small yet meaningful optimizations is an extraordinarily high bandwidth filter network, which is remarkably transparent to transients and current-demand dynamics. 

Jim obviously has a deep passion for precision, and leveraging the finest materials and workmanship to approximate as closely as possible the ideal of an invisible and absolutely neutral PLC. Needless to say, after years of denial, my expectations for the TT-7 were astronomically high. Even with that, the experience of it well exceeded all my expectations.

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Listening Impressions

The TT-7 sits between your home wiring and your devices, so you want to make sure that it is getting as much instantaneous current as it needs, and is able to deliver the same to your devices. For these listening tests, I initially started with an Elrod Power Systems EPS-3 Signature power cord between the TT-7 and my dedicated 30A audio circuit with 10-2 Romex wiring. 

Note that my audio equipment is not drawing anything near 30A. The intent of heavier gauge home wiring is to be able to deliver instantaneous peak power without slowing things down or being a bottleneck. This particular wall circuit is wired with 10-2 Romex (typical for 30A circuits to things like electric water heaters) straight back to my main home electrical panel, so is capable of delivering significant instantaneous current when required. 

However, after hearing what I’m hearing, I am wondering if even more robust wall wiring could help my system be even faster. A post-Pandemic upgrade of my dedicated audio circuit wiring to 8 or even 6 gauge conductors (typical for 40A and 55A circuits) is definitely bubbling up to near the top of my audio To Do list. 

From the TT-7, I used heavy gauge Pangea cables to power the Sean Jacobs DC4 (to Chord DAVE) and the bass units for my Voxativ 9.87s speakers (each with a 200W class AB amp). From the TT-7 and my Taiko Audio SGM Extreme, I used my reference Sablon Audio King power cable.

As a word of caution, remember that the TT-7 conditions power from the outlet to your devices, but if you have a noisy device plugged into the TT-7, all other devices plugged into the TT-7 will be exposed to the noise from that device (the TT-7 does not condition power between devices). Jim suggests that devices with the most power draw be plugged into outlets farthest away from the power switch, and that the noisiest devices be plugged in to the outlets closest to the power switch. 

Jim also suggests that the more power you draw through the TT-7, the better it performs. Alas, since I have high efficiency speakers that I directly drive from my DAC, I no longer have large amplifiers to test this in my system. However, curiosity got the best of me, and in a fit of pandemic-induced audio lunacy, I MacGyver’ed together a test load to add to my TT-7 (~1000W), and I can confirm that sound quality (mainly soundstage, which I’ve come to learn improves with lower power line noise) did actually improve(!) In speaking with several other folks that do have power amps plugged into their TT-7’s, they did all confirm that contrary to conventional wisdom, having large amps plugged into the TT-7 were an improvement versus plugging the amps directly into the wall.

First Impressions – PGI TT-7 Straight Out of the Box

Out of the box, I did not yet have an appropriate power cord with a 20A IEC connector, so I made due with a cheap 15A to 20A IEC adapter from Amazon (non-ideal, but better than no power). 

I first moved the bass units of my speakers to the TT-7 (leaving the Sean Jacobs DC4 powering my DAC plugged straight to the same dedicated 30A circuit as the TT7, and the Extreme plugged directly to a different dedicated 30A circuit). I was immediately struck by a significant increase in bass dynamics, with far greater control than I had heard before (and the Voxativ Pi-Bass units are already next level when it comes to dynamics and control, so to hear any improvement was a surprise). String instruments and horns revealed a new level of resonances, and more critically for me, the sense of “seeing” the space where the recording was made became much more vivid. Wow, what a great (and unexpected start) to this PLC adventure.

Next I moved the Sean Jacobs DC4 powering my DAC to the TT-7. Again, the increase in dynamics and transparency and improvement in imaging and that incredible holographic-all-around-you sound stage was astonishing, with an unexpected but welcome significant increase of a sense of relaxed control (which I usually associate with reducing the noise floor). I thought I was already at the top of DC4 mountain, but the TT-7 took it higher still.

As a final piece of the puzzle, I moved my Extreme from direct to wall socket on a second dedicated 30A circuit, to the TT-7. The Sablon King had already had a huge impact (to say the least) in my system, so I wasn’t anticipating much improvement. In fact, based on my previous power experiments with the Extreme, I was concerned that the TT-7 could actually slow things down for the Extreme. I was completely and very happily wrong.

Going through the TT-7, all that essential Extreme goodness (incredible dynamics and speed, huge sense of relaxed openness in presentation, precise (yet effortless) control, etc) were all materially elevated. The incredible lift I heard when I first heard the Extreme with the Sablon Prince (and later the Sablon King), was amplified at least 2x with the TT-7. The TT-7 is the first device I’ve had upstream of the Extreme that not only doesn’t slow it down, but it makes it feel faster and more controlled. That is a remarkable achievement.

To give a sense of what I’m hearing with dynamics, prior to the TT-7, I would very occasionally (rarely?) have a mild startle response on a percussion strike. This was a first for me, and hinted that the dynamics being generated by the Extreme were approaching what our low-level lizard brain would consider reality. 

With the TT-7 in line upstream of the Extreme and DC4, I am regularly experiencing a startle response on certain recordings. Those that have been in the same room as someone playing drums know what this feeling is. The TT-7 has clearly taken the Extreme into a new realm of dynamics. The incredible thing is that this is happening with a passive device between the wall and the Extreme. It speaks volumes to the adverse impact of grunge the TT-7 is filtering out, and how little (if at all) the TT-7 is slowing things down as it cleans up the grunge.

Switching out the 120V PGI TT-7 for the 240V PGI TT-7, everything that the 120V PGI TT-7 did got taken up to another level. In particular, I would not have thought it possible for the noise floor to crash any lower or dynamics could be any faster or more controlled, but that is what was immediately apparent. The choice of the 120V PGI or 240V PGI is not a difficult one for me, but as mentioned earlier, they are each suited to different situations. As always at this level, it is important to hear things in your room with your equipment and your local power grid and with your ears, and see what works best for you.

The PGI TT-7 is (to say the least) completely transformative in what it is allowing my audio components to do. It is incredible what a foundation of very clean “wall-outlet-fast” power reveals about what every other component in your system is really capable of.

(As an aside, interestingly Jim does a lot of his fine tuning of the TT-7 using a video display plugged into the TT-7. While it is outside the scope of this review, at Jim’s urging I plugged my LG OLED TV into the TT-7, and it had a truly remarkable impact on video quality – detail, dynamic range, color depth are all WAY better than I’ve experienced before. Amazingly, what the TT-7 does for audio, it also does for video, and anyone who takes video as seriously as many of us do audio would be well served to consider adding a TT-7 to their AV system. When it comes to video and audio, the TT-7 has a first couple seconds “holy crap that’s amazing!” impact.)

Detailed Listening Impressions

Before settling into some extended critical listening, I decided to build a proper 20A power cord to connect the TT-7 to the wall (unfortunately Mark at Sablon Audio is backordered, so he won’t be able to get me a second Sablon King for another month or two). 

Rather than using a stock 20A cable with questionable internal connections, I acquired some stock 12 gauge power cord (typical for 20A circuits), and Jim was kind enough to provide me a hospital grade connector to the wall outlet and a 20A IEC connector. After swapping in, it was very clear that the generic 15A to 20A IEC adapter I had been using with my Elrod EPS-3 Signature had not been doing me any favors – things were that much better still. 

So with things reasonably settled (at least until I’m able to listen with a Sablon King from wall to TT-7), time for some extended critical listening with the Sean Jacobs DC4 and my preferred Sound Application 240V PGI TT-7 (for details on each track and what I listen for for each, please see the end of the first part of my review of the Taiko Audio SGM Extreme)

Todd Garfinkle of MA Recordings is a gifted musician, and he brings that musician’s sensibility to all his recordings (you can find links to download both a high resolution music sampler and regular resolution sampler on Todd’s homepage…every track is a gem). Using a single stereo microphone, he captures performances that put you in the time and place of the performance. With the DC4 and TT-7, the sense of being there is absolutely remarkable.

On Murakkaz Ah Ya Muddasin (from “The Splendour of Al Andalus” by Calamus), there is incredible detail and dynamics, without coming across as “hot” or out of control (as this track can be prone to do). Control is rock solid, even with challenging congested phrases. Amazingly, the soundstage has now become a true surround soundscape, extending well behind and around me. The sense of space is incredibly real, but not exaggerated or artificial. 

On Noche Maravillosa (from “Salterio” by Begonia Olavide), the resolution and detail and dynamics of the percussion and strings is well beyond what I’ve heard before, with that telltale startle that lets me know that we’ve moved into a new realm of dynamic speed. Again, with the DC4 and TT-7, the performance has gone from 180 degrees to a full 360 degrees. This is a true soundscape, with the musicians and room fully articulated and natural. 

On Voglia Di Vita Uscir (from “Buenos Aires Madrigal” by La Chimera), all the nuance and coherence I love in this performance has been enhanced to the next level, but I’m struck by how relaxed and controlled the presentation is. These are performances that invite you in and envelop you, and what a joy it is to fall into this level of artistry with this level of nuance subtlety!

Ivan Fischer’s Mahler #2 is an incredible recording and performance, carrying your emotions as the performance weaves through spectacular dynamics. The entire orchestra and hall is here, with each performer (almost) being distinct, and the coherence of the orchestra is simply lovely. The control and impact and detail through the bass is fierce, and the dynamics of the percussion take your breath away. Experiencing large scale orchestral pieces like this makes me appreciate why so many are so enthralled by these majestic performances. 

Listening to my long time favorite Arensen “Magnificat” (TrondheimSolistene) has become like hearing it anew. On “Et Misericordia”, the organ and strings and choir and cathedral truly become as one – the experience rolls over you and around you and above you and within you. We have all experienced those precious glorious moments in live performances that link you with the performers and the space and the people around you, and take you to a different place. In these times of forced distance and isolation, it is remarkable (and a gift) to be able to experience this level of collective musical transcendence in my home.

It is always a treat to revisit the gift that is Shamus-Ud-Doha Cader-Ud-Doja (Ustad Nusrat Fateh Ali Khan) after a major system upgrade. Again, the master has me in tears from his opening call. Can this possibly be the “eh” recording of a transcendent performance that changed my life almost a decade ago? The performers are pouring out their hearts and souls for each other and their God, and my heart and soul are joining with theirs. There is nothing lacking here – the dynamics, the soundstage, the emotion. The ability of the DC4 to elevate marginal recordings to very good or even great recordings is a remarkable gift, and the ability of the TT-7 to amplify what is special in all my components makes it completely transcendent.

Eva Cassidy’s Fields of Gold (from “Nightbirds”) is another recording where the remarkable performance was left short by the recording. The incredible control and dynamic speed of the DC4 and TT-7 have finally elevated this recording to the place I always wished it was able to go. When a component is able to transform beloved but neglected recordings into true audiophile experiences, it is like reconnecting with old friends after far too long, but with the benefit of wisdom and appreciation that comes with time.

As I work through my review playlist, I am again and again struck by the immense soundscape for recordings that never really had that sense before. Seemingly all my recordings have become holographic binaural recordings, with incredible resolution and detail, and all the resonances that suck you into live performances. Hearing the musicians not only perform with incredibly nuanced artistry, but also hear them listen to their instruments and to each other and react to each other is remarkably engaging. 

A huge part of this is the custom upsampling pipeline I use to preprocess (effectively remaster) all my tracks (briefly described at the end of this review), but the DC4 and TT-7 are absolutely essential to fully revealing that vast all-enveloping space and performance. With the DC4 and TT-7 the proportion of my music library where I am able to experience this level of engagement is at least an order of magnitude larger than what it was before. Welcome back old friends.

As I venture off list, I am struck by moments of what I can only describe as musical intimacy. Each of us has music that is wired directly to our souls, often from our youth or moments in our lives where we were imprinted with an emotional milestone. It is quite something to hear songs that are part of your DNA presented in this way. 

Hearing a young Elton John earnestly sing “Tiny Dancer” or a Paul McCartney on “Golden Slumbers” gives you a peek into their hearts and hopes during a time in their lives that is long gone. These are real people, and they are sitting with you, even if displaced in time by half a century. Your heroes and shamen and those that spoke for you when you did not yet have the words to speak for yourself – all of a sudden they become manifest, real people with real hopes and real demons. Quite something to hear these essential truths, and know that they were there all along in the music, just waiting to be really and truly heard.

As always, I close out my listening session with Mile Davis’ So What (from “Kind of Blue”). With everything I’ve been hearing over the last several weeks, I’ve been eagerly waiting for this moment. A chance to hear Davis and Evans and Cobb and Coltrane and Adderley and Chambers at the exact moment the universe aligned over New York City in 1959 should have been a once in a lifetime thing. With the DC4 and TT-7, it is the closest I’ve heard to experiencing that moment again.

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So What Is Happening Here?

Clearly, better power (both DC and AC) has a remarkable effect on digital playback. When listening to old favorites, even for the best performances, there is a whole new amazing dimension of artistry that has always been there, but that has somehow always been held back.

With the Chord DAVE DAC, even a world class DAC benefits with better digital power, amplifying all the attributes that makes the DAVE so engaging and enthralling: amazing transient timing, incredible whole room holographic imaging, and remarkable detail and resolution (with incredibly visceral and physical and fully resolved bass). More importantly, it gives the output of DAVE significantly more authority and control, resulting in massive increase in dynamics and control, all while reducing strain and noise floor all across the board.

As an unexpected benefit, with a world class power supply like the DC4 powering the Chord DAVE, the radically improved dynamics and control makes everything sound like it was remastered, and darkness of backgrounds makes it seem new. Great recordings sound even better, but “eh” recordings are transformed and reborn as good or even great recordings. 

So what is going on with the DC4 and Chord DAVE? Recall that earlier I mentioned that the DC4 CX regulator boards have a special filter circuit to reduce noise significantly below the DC3 at lower current levels, and that this filter can be enabled and disabled using a jumper on the regulator board. So would toggling this filter give us any insights to what attributes of the remarkable sound I am hearing are impacted by power?

To evaluate the impact of this filter, I first bypassed it for the ±15V rails, then the 5V rail. 

When the CX filter was disabled for the ±15V rails (analog) the incredibly relaxed presentation got more stressed, and control on dynamics perhaps a little less confident. These attributes were still better than my DC3, and still significantly better than the stock Chord SMPS. Clearly, noise on the ±15V rails (even if very small) has a tangible impact on presentation.

When I disabled the CX noise filter on the DC4 5V rail (digital), stress increased, but a lot less than with the ±15V rails. More interestingly, the much more significant change was significantly less depth and openness in the soundstage. Noise on the digital voltage line clearly impacts that amazing sense of depth and space that I love about the DAVE (in my experience, the most easily disrupted of DAVE’s distinctive attributes). If you cherish the coherence and sense of space from a Chord DAC, be rigorous with the power you deliver to the digital section of the DAC.

While noise matters, ability to deliver fast current has a huge impact on dynamics and control and soundstage. Large transformers, big caps on regulator boards, and multi-stage voltage regulation simply have more dynamic reserves than a typical small switching supply. 

Both the DC3 and DC4 completely transform the DAVE, and make listening a fundamentally new experience. While the DC3 brings the soundstage deep into the room, the DC4 transforms it and brings it up to sit with you on the sofa. Both bring a level of dynamics and transient timing and control that completely beyond what the stock supply is able to deliver.

Although this review has been focused on the Chord DAVE, the mechanisms in play would certainly benefit all DACs. At the very highest end, manufacturers like MSB have embraced separate high quality power supplies for their flagship DACs. Sean Jacobs already provides very popular power supplies for Naim DACs. Even with my Chord Hugo TT2 DAC, there is a material improvement when powering the unit with a Paul Hynes SR4, and an even bigger step with a LDOVR DXP supply energized with a PowerAdd Pilot2 battery. Would other DACs benefit as well? In my view, absolutely yes.

On the wall outlet side of the equation, AC power is foundational for all components in your audio system, whether digital or analog. With a Sound Application PGI TT-7 in the mix, it provides an essential and exceptionally solid power foundation for all the components in your audio systems. All components (not just the DAC) benefit from cleaner power. Virtually all components (except for those with constant current loads, like Class A amps) benefit from “wall-outlet-fast” power under dynamic current loads. 

The TT-7 playbook is deceptively simple: aggressively filter noise from wall power, and appear to all your components as if they were directly plugged into the wall. Easy to say, but taking 30 years of obsessive focus to deliver on, and deliver the TT-7 most certainly does.

In my system, with the Sound Application PGI TT-7, every component in my system has had its strengths become a superpower: 

  • The super fast and controlled dynamics of the Taiko Audio SGM Extreme get kicked to a completely new level (an absolute first for me to have anything upstream of the Extreme not only not hold it back, but to actually make it better).
  • The remarkably fast and precise Pi-Bass units of the Voxativ 9.87’s are now able to coherently present all the deep room resonances that make perception of a space real, and takes the already considerable bass control of these units to a shocking level of precision. 
  • All the remarkable benefits of the DC4 powering the Chord DAVE are amplified and become all enveloping. The already remarkable soundstage becomes a full sound scape, extending past the sofa and giving a vivid sense of the entire space the recording was made in (up, down, and all around). 

Remarkably, every component being better makes every other component better as well. The monster dynamic of Extreme going to Godzilla levels makes the incredible transient timing performance of DAVE transformational. DAVE’s remarkable transient timing and imaging get elevated by the DC4 performing better and with less noise. The DAVE having an order of magnitude better dynamics and control allows it to better take advantage of the amazing speed of the Voxativ 4D 102dB sensitivity speaker transducers. The black hole dark low noise floor with the TT-7 makes the soundstage all enveloping, and a level of engagement and relaxed naturalness of the presentation makes the experience of listening to music even more real.

Looking forward, I would expect a second Sablon Audio King power cord from the wall to my TT-7 will take these remarkable dynamics even higher (I suspect my home made 12 gauge power cord is the bottleneck right now), but I would expect the black hole dark noise floor with the TT-7 to stay the same. 

UPDATE (2/26/21): I have received my second Sablon Audio King power cord (20A IEC, from the wall to my TT-7). (Un)Surprisingly, adding the Sablon 20A King on TT7 PGI 240V is another first 3 seconds “I’m done here, no more listening tests needed” experience, even before burn in. There is a magic synergy going the wall to Sablon King to TT7 to Sablon King to Taiko Audio SGM Extreme. If you’re investing in a Sound Application TT7, do yourself a favor and track down a Sablon King power cord to audition with it.

WIll heavier gauge wiring back to my electrical panel take dynamics even higher? My spidey sense says yes (although I’m not looking forward to explaining to my electrician why I want to run 6 gauge wiring to my audio outlets). Post pandemic, when restrictions are lifted, we’ll find out.

Based on what I’m now hearing with my Voxativ 4D drivers, I am also now extra keen to hear what the even faster 106dB Voxativ 4ɸ speaker drivers could reveal in my system.

And is there more to be had with even better DC to my Chord DAVE? Could dual regulated Paul Hynes rails elevate things further? How about Mundorf silver/gold wiring for the umbilical? Is it time to consider separate supplies for the digital and analog sections of DAVE, to minimize any crosstalk? Certainly, getting answers to these questions have now bubbled to the top of my audio to do list.


So Is it worth risking your Chord DAVE and your health to install an aftermarket power supply? 

In an ideal world, all DAC manufacturers would externalize their power supplies, and we’d have freedom to mix and match supplies as our budgets and sensibilities allow. In the real world, I can’t imagine the customer support nightmare when customers plug in questionable supplies and fry their very expensive equipment. 

Alas, there are very pragmatic reasons why DAC manufacturers are compelled to build supplies into their DACs (almost universally these are switching supplies). Doubling costs by having separate cases with expensive transformers and components does not help drive sales, and how many customers will care enough to justify that level of investment?

So for those of us that want the most real and immersive and engaging experience we can have with our music, we’re left with getting out the multimeters and going all Doc Brown on our DACs. To reach the very highest heights of what’s possible in musical reproduction, you need to break out the tool box. C’est la vie.

For me personally, the upside is so profound, that the risk (and investment) is a no brainer. A supply like the Sean Jacobs DC4 completely elevates the Chord DAVE to what I believe to the finest in the world. My purchase of my Sean Jacobs DC3 for my DAVE several years ago was the best audio purchase I ever made not because of the DC3, but because it made my DAVE even more of the best purchase I’ve ever made. The DC4 just elevates the DAVE further into the stratosphere.

In digital audio, for me it is all about the Server + DAC + transducer. Everything else is about not corrupting or holding these back and extracting every bit of magic you can from them. The Sean Jacobs DC4 certainly delivers for my Chord DAVE, but the Sound Application PGI TT-7 releases a torrent of dynamics and crushes the noise floor for all my components. 

The TT-7 is lightspeed fast, transparent and relaxed, and remarkably detailed and controlled, and it makes all my components the same. More importantly it takes the strengths of all my components and transforms them into a superpower. 

Based on my experience with the TT-7, I am now adding a Third Law for digital audio optimization:

  • First Law: Invest in cabling, power, and digital hygiene to do as little harm as possible (directly or indirectly) to the DAC’s clock, ground plane, or reference voltage plane
  • Second Law: Invest in a digital endpoint that moves bit perfect digital data from ethernet to a USB DAC with as little variability and as much timing and signal integrity as possible (aka, as close to precision real time data streaming to DAC as possible)
  • Third Law: Invest in the cleanest and fastest and highest capacity power delivery to all your audio (and video) components

Like my Taiko Audio Extreme, Chord DAVE, and Voxativ speakers, the Sound Application PGI TT-7 is now a key foundational element of my system. For audiophiles with the means and interest, I would urge you to audition the TT-7 in your own system, and relish how it amplifies everything you love in every other part of your system. It simply makes everything (including your TV!) remarkably better.

But at the end of the day, for me it is always about the experience of the artistry and emotion of the music. As things become more real in my living room, my connection to these performances and these truths gets exponentially more profound. As I hunker along with the rest of the world in a very dark winter, the light and warmth of the truths I’m surrounded by right now is overwhelming, and most welcome.

It is also humbling for me to realize that all the talent and emotion and art that I am now experiencing in such a profoundly new way has always been there, just waiting to be heard. These truths were waiting in these recordings all along, and through meticulous engineering and attention to every detail, we’re finally able to hear them. Many thanks to Sean and Jim for the opportunity to hear these truths in this remarkable way.

Best wishes for a safe, happy, and hopeful New Year!

– Ray

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For those with the patience to have made it this far, thank you (I now owe you another beer). 

For me, taking these deep dives into the designs of engineers like Sean Jacobs, Jim Weil, Emile Bok, Rob Watts, and Inés Adler are taking a master class in what really matters in digital audio, analog audio, and power. These are world class designers and engineers with meticulous attention to detail. Deep dives like this gives me a small peek into the deep expertise and experience of these masters, and I’m hopeful that it is helpful to fellow travelers.

My sincere thanks to all those in the digital audiophile community that have blazed the way for power optimization (DC and AC), with most of that trailblazing happening right here at (Computer) Audiophile Style. Your work and generous sharing of experiences is incredibly appreciated, and it has been incredibly rewarding to walk the trails that you’ve blazed. Special thanks to @romaz for not only introducing me to Jim and his patient encouragement to give the TT-7 a proper audition, but also for sharing his invaluable experience and insights on how power and noise impact digital audio.

Finally, a special thanks to those that contributed insights and feedback on this review, and those patient enough to have given your time and attention to get to this point.


Below is a final snapshot of my current reference system:

reference system diagram

Although seemingly complex, I am going fiber internet from the street to ONT to EdgeRouter to opticalModule to Extreme to USB to Chord DAVE to speaker cables to Voxativ 9.87’s. This is the simplest and most transparent system I can imagine, leaning heavily into the design and engineering genius of Emile Bok (digital servers) and Rob Watts (digital to analog servers) and Inés Adler (analog transducers). 

For this review, Jim Weil’s PGI TT-7 brought cleaner faster power to all my components, and Sean Jacob’s DC4 brought next level power and dynamics and imaging to my DAC.

DAC and DAC Power – Review Setup
Chord DAVE
Custom Sean Jacobs DC4 3 rail supply ($7,300 as reviewed)
Custom Sean Jacobs DC3 3 rail supply (~$2,500 as reviewed, but discontinued)

AC Power – Review Setup
Sound Application PGI TT-7 Power Line Conditioner ($15,000 as reviewed)
Sound Application 240V PGI TT-7 Power Line Conditioner ($20,000 as reviewed)
Dedicated 30A circuit (10-2 Romex) connected to an upgraded high conductivity outlet
A variety of upgraded power cords, ranging from a Pangea AC-14SE to an Elrod Power Systems EPS-3 Signature to a Sablon Audio King power cord 
Synergistic Research Orange fuses on Extreme and DC3 supply

Digital Source
Taiko Audio SGM Extreme

Direct Two Channel Setup
RCA direct to Voxativ 9.87’s with Voxativ 4D drivers
Voxativ Ampeggio speaker cables

Monoprice USB SlimRun optical USB extender cables
Sablon Audio 2020 USB cable

Vibration Control
Daiza vibration Isolation platforms
Custom precision rollerball isolators

My Go-To demo tracks and what I look for in each are detailed in the first part of my review of the Taiko Audio SGM Extreme. For this review, all these tracks were off-line upsampled (using a custom software package currently in private beta) to 16fs (705/765kHz, 32 bit) to match the input pipeline of the Chord DAVE. The custom upsampling pipeline is optimized to maximize time domain accuracy in reconstruction, and minimize noise in the audio band. The result is an exquisite and natural holographic soundstage with remarkable timing accuracy, all of which is an excellent test of what a Chord DAVE is able to deliver at its best.

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