iFi audio Pro iESL + KingSound KS-H3

by Dawid Grzyb / July 19, 2018

Turntables, CD players, electrostatic headphones and any equipment associated with either of these is what yours truly stays away from. Still, some things happen whether we’re prepared for them or not. One energizer and a pair of matched headphones – iFi audio Pro iESL and KingSound KS-H3 respectively – were sent to me and are this report’s main dish. Enjoy!


This scribe avoids products listed above deliberately. In his case, a very limited experience with these (or no experience at all…) determine what’s not on the HFK menu. It’s simply good to know what one is capable of. This site’s goal is to paint as professional picture as possible each and every time. In order to achieve that, a level of expertise is mandatory as without it no regular review can be done. Any attempt to tackle a subject very much unknown defeats the purpose of this very place. And yet, once in a while something happens, pushes us to step outside of our comfort zones and things move from there. That’s exactly what happened this time around.My ride with electrostatic headphones is very mild. I’ve heard these many times already, yet an opportunity to give any particular model the usual go, namely undisturbed, for several days at least and at my own place… happened just recently. That’s something far different from short auditions in noisy environment associated with audio events. These net only a brief insight into a given product, merely scratch its surface, thus serve as teasers of things possibly yet to come and nothing else. Still, the package sent from iFi audio directly sported two very peculiar products meant to work as a team, turned out to be an incentive good enough to conduct a proper investigation and this material is the result. The electrostatic experience started very innocently at my place, with no intention of putting it into words. One thing led to another and several easygoing sessions eventually flourished into something worth sharing. Even though this writing might look like a full-fledged review, it’s anything but, simply because the electrostatic turf is quite new to this reporter. Therefore please see it as a commentary made by one curious individual, thus far into dynamic and planarmagnetic cans exclusively.

iFi audio Pro iESL

iFi audio has built a reputation of a brand very much into non-standard products. In its portfolio there’s of course a number of the usual suspects; portable DACs, headphone amps and quite a few integrated solutions. Additionally this very much mainstream line-up is topped via various tweaks and gadgets designed to target specific issues, namely ground loops, jitter, noise and such. Sorting service i.e. iGalvanic3.0, iDefender3.0 and iUSB3.0 provide puts iFi audio in a very unique spot no other company known to me is. The iFi people walk their own walk; they think and act quite differently and after several years in the audio game that’s very clear to someone up to date with their moves.Most iFi audio products are affordable by today’s standards. This rule applies to goods from the nano and micro range and all its gadgets as well. Still, if one wishes to push things further yet remain faithful to the iFi audio brand, its fully desktop and pricier Pro family is the current pinnacle. The Pro iCAN writing is to be found here, whereas the latest product – Pro iDSD – might be seen at HFK soon. What’s left is this material’s hero – the Pro iESL.iFi audio Pro iESL is an energizer, thus a product which delivers high voltage needed for electrostatic headphones to sing as these won’t go with regular amplifiers. Put shortly, iESL energizes these peculiar cans, but can’t work on its own. It has to be fed either via speaker terminals of a regular stereo power amp, iFi audio’s Pro iCAN or any other headphone amplifier loaded with XLR outputs and enough juice (at least 10V into 64Ω). All things considered, iESL is not a regular deck to play with and as such it’s for enthusiasts already in the electrostatic know. A ‘niche inside of a niche’ affair, then? You betcha, though delivered in a very modern and features heavy package.Pro iESL comes in a regular iFi audio Pro series size of (WxDxH) 2013x206x63mm and weighs hefty 2.5kg. Its aluminium enclosure’s front and rear are brushed, whereas everything else is sandblasted. Openings found on its top and left side form a round pattern with a small magnifying glass in the middle. All this looks very tastefully. Pro iESL’s front sports four knobs in total. Two bigger selectors allow one to set desired input and driving amp’s load impedance, whereas AC termination and bias are adjusted via smaller ones and in-between these there are three headphone outs in total; 6-pin (older Stax), 4-pin XLR meant for regular cans and 5-pin (modern Stax). Available options are generous, I was told that there are no electrostatic cans iESL wouldn’t handle.The machine’s rear is interesting. Several pairs of speaker terminals found there indicate how Pro iESL can be used. If fed via a regular speaker power amp, it’ll work in-between such a product and a pair of speakers, thus in a pass-through fashion. Alternately one can use a single 4-pin XLR input right next to binding posts. How? Some balanced headphone amps can work as full-fledged preamps loaded with 3-pin XLR outputs, though a suitable adapter to marry such a product with Pro iESL is a necessity in this case. And lastly, the most friendly option is iFi’s proprietary ESL link. This HDMI based interface allows one to connect this company’s energizer to Pro iCAN directly. It’s seen right from the get-go that these two boxes were meant to work as a team. Once stacked, they look nice and a single PSU is enough to power ’em both. In this scenario Pro iESL effectively becomes fully operable only via one short cable included in its package and that’s all it takes.Once Pro iCAN is turned on, so is its energetic kin but there’s more. XBass and 3D adjustments the former provides are heard on the latter’s outputs. It’s also important to know that Pro iESL doesn’t have its own volume control. It’s safe to think of it as an electrostatic power amp, which needs to be regulated via a machine one step earlier in the chain and here Pro iCAN’s volume knob was on the job in my case. Moving to Pro iESL’s innards, the on-site description paints a very accurate picture of what this machine really is. iFi audio developed its own transformer, code-named PPCT (Pinstripe Permalloy Core Transformer). Its core is a mix of Mu-Metal lamination and GOSS (Grain Oriented Silicone Steel). Ultra-wide bandwidth, linearity and reduced distortions were the clear goals and – according to iFi audio – careful merger of these two materials allowed to achieve them. Each transformer is hand wound within the company, the winding pattern is multi-sectioned horizontally and vertically and the wire itself is extremely thin. Voltage bias in Pro iESL is executed via two large banks of WIMA film capacitors rated at 1,000V DC. These charge up to a required voltage, then are turned off to ‘float’ at desired bias level.

KingSound KS-H3

Electrostatic headphones are considered as luxurious goods for a perfectly valid reason. One quick glimpse at Stax or Abyss offerings is more than enough to understand that this adventure is a costly one even early on. To push things even higher, Sennheiser’s and HiFiMan’s top tier electrostatic products have mid five figures on their price tags, thus are available for very wealthy individuals exclusively.KingSound is a brand very much into electrostatic audio hardware but far easier on your wallet. Its portfolio consists of four electrostatic floorstanders and the same number of amps suitable for these, all loaded with tubes. Headphone decks are three in total, one of which is fully portable and battery based. This review’s hero – KS-H3 – sits in the middle of the KingSound’s headphone threesome and priced at around $800 (new) is in fact one of the most affordable electrostatic options available on the market these days. Too good to be true? That’s what I intended to find out.KingSound KS-H3 is an open and circumaural design. On hand it feels suspiciously light. Along with a rather long ribbon cable finished with a 5-pin plug, the product’s mass is slightly less than 0.5kg. Still, that dissonance fades away once KS-H3 is at work. Long audition hours without any signs of fatigue is the early impression. After all, the lighter a pair of headphones is, the better.Heavily perforated earcups and outer swivel enclosures suggest that KingSound KS-H3 is made mostly out of aluminium, which is good. Closer inspection reveals that all these elements are not on the same level in comparison to pricier products by other manufacturers, though there’s no reason to be picky once the product’s price is taken into account. Yokes are steel and so is the upper headband’s piece. The latter doesn’t come in contact with one’s head and is fixed, whereas a leatherette strap found a bit below and mounted via two pieces of elastic provides necessary adjustments. As far as comfort went, there was no reason for me to complain.Soft and big, leatherette covered earpads turned out to be not as deep as I’d like. The outcome was that my fairly small ears were all surrounded nicely, but slightly pressed via protective mesh inside. No sensation of this sort happened with my HiFiMan HE-000V2. In any case, this was a minor issue. I also enjoyed the possibility to twist earcups by 90 degrees to effectively make the product flat and easy to transport via solid carrying case included in the package. The only thing that I truly disliked were plastic inner pieces of both swivel enclosures. They stayed in place screwed in firmly, yet felt very tacky.In case of regular mid-tier headphones, a fixed signal cable is a major drawback. But I haven’t yet seen electrostatic cans with a leash any other than stock one and probably there’s a reason why this is not easy/possible to pull off. All in all, comfort and build quality wise KingSound KS-H3 is perfectly fine once its ask is taken into account. This is honestly built yet not a luxurious item. I got the impression that it never was designed or priced to aspire as one, which is fair.


I rolled with the most easygoing and convenient setup I could pull off within my own four walls. LampizatOr Pacific (KR Audio T-100 DHTs + KR Audio 5U4G rectifier) was fed via my trusty ‘ol laptop and then connected to iFi audio Pro iCAN, which fed the Pro iESL via this manufacturer’s HDMI based link. At some point HiFiMan HE-1000v2 were used and the confession down below is based on such a setup exclusively, no additional DACs or power amps were involved. As an electrostatic freshman, I saw no reason in any additional triangulation. One easy to use setup was perfectly fine in order to properly grasp the general concept and possibly move from there in the future. Alternatively you can label me as lazy, it’s fine.Although my electrostatic ride was thus far brief and limited to auditions during shows, a number of such encounters allowed me to flesh a general idea of what products of this sort do. It didn’t matter whether I’ve heard goods by Stax, Abyss or brands not as popular, but to my very ears the sound all the electrostatic lot produced was always more or less similar; very open, clear, delicate, exceptionally airy and far too slim to my subjective taste. I haven’t yet heard a proper bass response from any of these. Who knows, maybe painfully expensive HiFiMan’s Shangri-La or Sennheiser’s Orpheus HE-1 are gutsier singers, but were never on my radar solely because of their staggering price. Perhaps these two would do the job, I can’t say. In any case, I thoroughly enjoy their looks, see both of ’em as works of art and let’s leave it at that.When KingSound KS-H3 arrived, the initial impression was very similar to what I’ve already heard in the past. The sound was lean, spacious, delicate and very airy. Back then I took this early experience for granted and saw no hope for things to become any different. The joke was clearly on me as the whole setup in time revealed as something far more potent and enjoyable. Put shortly, there was so much more to it than I assumed early on. The missing factor was accommodation time and what followed was very revealing. The electrostatic rig assembled grew on me extensively, to a point where I finally understood why some people roll with electrostatic headphones exclusively for years without taking anything else into account.This writing’s main setup didn’t sound linear. It actually was as far from tonally even as possible. At this point one could think that something was off. But the more auditions were in the past, the more obvious it became that all this was deliberate. There is a perfectly reasonable method in this madness and in order to paint more understandable picture, let’s invoke Xavian Perla monitors. These very peculiar performers have their sound very much midrange focused, that’s the base. And everything else, be it trimmed highs or fairly limited bass response, is on the supportive job. It’s not about linearity in this Czech case but rather a listener’s attention on what’s in-between, i.e. vocals. When Perlas are on, I don’t think about things missing or not sufficiently audible but focus on sheer joy its sweet and plainly warm mids provide instead. Such tuning simply works like a charm if you’re into it. Not each and every time, but when Roberto Barletta’s petite boxes are on, subconsciously I’m in the right mood to enjoy them. Put simply, this is not a very universal product to listen to, but surely is a proper tearjerker tuned very tastefully to my ears by someone very much into music. Either an individual can resonate with this or be off to a product more suitable to his/hers liking. Audio is about variety, not one but many righteous ways are out there. No downsides visible on paper but being different and subjectively very good is the case with those Xavians. Now getting back to this review’s main rig, its story is not exactly the same, but quite similar nonetheless.The electrostatic setup I assembled delivered midrange oriented performance, but everything upstairs was on the pedestal as well. The audible pinnacle was very clearly defined and present though not overly shiny and with right music it stole the show. My HE-1000v2 didn’t reach this high and weren’t this clear, though the difference in high FR exposure between the two was only a part of far grander scheme. KingSound KS-H3 sang exceptionally openly and not densely at all, at least not in the regular way. The amount of details these cans served was generous, but most importantly in very smooth, delicate and tangible fashion. If not matched mindfully, the usual dynamic or planar suspects with such an attitude would’ve fatigued me very early on presumably, but this material’s hero seemed to be too suave to do this. In its case, elevated highs boosted clarity and also made imaging very expansive and the ambience rather felt than heard. When limited bass reach and presence were added to the mix, the sensation very much ethereal and unique to the electrostatic breed was the outcome. On this count precisely, all such specimens known to me operated in the same realm, even via short auditions at various shows it was a breeze to notice this specific profile. That’s how clearly it’s embedded in the electrostatic performance.The obvious drawback to many individuals will be KingSound KS-H3’s bass response, just as I’ve explained. The difference between these cans and HE-1000v2 is nothing short but staggering. Not only the latter is generous and of quality in this regard, but the former seems to sport no bass at all in comparison, thus makes everything above very articulate and not veiled at all, though unnaturally light. Here Pro iCAN’s XBass feature turned out to be quite the efficient workaround to a degree. This fully analog implementation impacts low FR only with its boom susceptible upper band in check and everything else properly clear in effect. But the limited bass reach downstairs serves as an additive still. Being familiar with a number of fit midrange focused speakers, once I was able to grasp the general electrostatic concept my loaners sported, this was of no issue for me personally.Again, instead of thinking about things not present/available, my attention subconsciously shifted towards pleasantly textured bass tissue and enjoyably euphonic mids topped with generous upstairs reach and decay. Just as it was the case with Xavian Perla, it took me a while to adjust to this sound and various repertoire experiments were conducted to enjoy the trip even more. But once I’ve found my niche, this adventure was truly enjoyable indeed. The secret sauce turned out to be live instruments and vocals. A spot on recordings of this sort were the assembled setup’s bread and butter. Not a hint of grain, sweetness in check and perfect clarity, smoothness and vividness blended tastefully to my ears netted sophisticated and seasoned effect. The outcome this mature and engaging was the reason why bass leaner than I’m used to was no issue at all. But that’s just one man’s subjective tale.


The first proper electrostatic experience I’ve found peculiar as expected, yet very enjoyable in the long run. All it took to arrive there was my own mindset’s adjustment, which happened naturally in time. All things considered, the HE-1000v2 as a daily driver is far more universal and as such it stays in the usual place. But the iFi audio Pro iESL and KingSound KS-H3 team delivered a very different and highly addictive sound nonetheless.

For now I’m not able to say whether this report’s heroes are worth their ask, I simply need to know them more and in order to do so, additional electrostatic hardware needs to be involved. But what I do know at this point is that – after familiarizing myself with this setup quite well – now I understand why some people take only electrostatic products into consideration as obviously there’s something unique and magical about ’em indeed. And now, to investigate more of that peculiar magic in the future is my sincere intent. ‘Till next time!

Associated equipment:

  • Amplifier: iFi audio Pro iCAN
  • Sources: Lampizator Pacific (KR Audio T-100 DHTs + KR Audio 5U4G Ltd. Ed.)
  • Transports: Asus UX305LA
  • Interconnects: Forza AudioWorks Noir, Audiomica Laboratory Erys Excellence
  • Power supply: Gigawatt PF-2 + Gigawatt LC-2 MK2 + Forza AudioWorks Noir Concept/Audiomica Laboratory Ness Excellence
  • Rack: Franc Audio Accesories Wood Block Rack
  • Music: NativeDSD

Retail prices of reviewed components in EU (excl. tax):

  • iFi audio Pro iESL: €1’575
  • KingSound KS-H3: ~€800


Manufacturer: iFi audio / KingSound