[BTD1]

yikes

maybe there is something you can put on it to kill the mold without messing it up

How well documented is this mold phenomenon? Why would this just be the case with the Shangri-La Sr? Was the person reporting in an overly humid environment? I have a pair due to arrive in the next week. I'd like to understand if this is a real universal concern or just one person's bad luck.

 

[number1sixerfan]

I can't speak to the driver enclosure or preventative measures that could be in place that aren't, or even if it's truly the case. But just mentioning that this is why it's so important to store e-stats properly. Mold shouldn't be forming in the first place if so.

I will say I'm starting to get a bit paranoid with a lot of my gear with the ever increasing price of these TOTL headphones. As soon as I move, I'm going to purchase humidity controlled cabinets, which I think someone has posted pics of in the stax thread. I currently use humidity packs in a nearly airtight drawer, but that doesn't really seem optimal either.

 

[Chefguru]

yikes

maybe there is something you can put on it to kill the mold without messing it up

Sad that this is a concern with a $18,000 headphone.

 

[Pastwa]

I'm going to purchase humidity controlled cabinets, which I think someone has posted pics of in the stax thread.

I don't think that any moisture that settles within the headphones comes from the room humidity (unless someone literally lives in a jungle) it it mainly (especially in a warmer conditions) the moisture that 'evaporates' from our skin/ear, especially if sitting longer with the headphones on (the inner cups don't get much ventilation and the moisture may get trapped) and some people could simply start to sweat.

 

[number1sixerfan]

I don't think that any moisture that settles within the headphones comes from the room humidity (unless someone literally lives in a jungle) it it mainly (especially in a warmer conditions) the moisture that 'evaporates' from our skin/ear, especially if sitting longer with the headphones on (the inner cups don't get much ventilation and the moisture may get trapped) and some people could simply start to sweat.

I've personally only ever seen or heard of mold forming within headphones in conditions from actual room humidity. Hence the purpose of the humidity cabinets for audio gear. But I could see it also happening with very frequent use if someone is literally profusely sweating and using them daily I guess.

In any event, I'm certainly not excusing there being a lack of protection, if that's actually the case beyond this one person's claims.

 

[smodtactical]

How does the bass of Shang Sr compare to tc?

 

[BassicScience]

How does the bass of Shang Sr compare to tc?

I've only heard the 1266 TC at shows, so you'll probably get more detailed comparisons if you post in @number1sixerfan 's "Quick Impressions" thread. The consensus seems to be that estats can't match the 1266 TC (or even the majority of planars) in terms of bass slam, and I would concur. The quantity and slam of the SGL's bass is more than sufficient for essentially everything I listen to nowadays (which sometimes includes hip hop, but not metal except on rare occasions). The texture and speed of the SGL's bass is superb, IMO.

As a final note, to date I've not heard the SGL on any of the TOTL estat amps, so its bass may actually be better than what I experienced. Again, you'd be better served to post your question in the other thread. Cheers.

 

[hifixman]

Just find this amazing review of tubes, not sure if the top 3 could be compatible to T2 electrostatic Energizer

https://wallofsound.ca/audioreviews...-with-tubes-supplied-by-www-thetubestore-com/

I was wondering if anyone has experience of rolling tubes of T2? While I love the clarity, control, and ease of PSVANE UK EK34, I do miss the slam and god send bass from Mullard and NOS which then sounds a bit muffled lacking control compared to the EK34.

 

[BassicScience]

UPDATED STAX SR-X9000 REVIEW

I procured my new X9K about three weeks ago, months ahead of when I was expecting it to arrive. I've done enough listening to it now to provide a more fleshed out review, and will also provide more of a comparison with the Susvara (instead of the Shangri-la, as previously).

X9000 Ergonomics

This is a rather light (432 grams) headphone with superb weight distribution due to the wide leather head strap. Clamping force is moderate (a bit less than the Susvara's) and ear cup capacity is generous. The large diameter ear pads apply light pressure to the corners of my jawbone, but otherwise you could almost forget they're on your head. In spite of the amazing comfort of the X9K, I actually rank the Susvara's comfort even a bit higher due to less contact with my jawbone, as well as better ventilation of the earpads and head strap. On a warm day, my ears and scalp (under the strap) can get a little moist from perspiration when wearing the X9K. Not a deal-breaker by any means, but worth mentioning for those in warm and/or humid climates. All that said, the X9K and the Susvara are both at or near the top of the list for most comfortable headphones I've ever worn. The cables (1.5 and 2.5 meter) supplied with the X9K are detachable (yay!), and very solidly constructed, if a bit bulkier and heavier than the (non-detachable) cables supplied with the Hifiman Shangri-la Sr./Jr. estats. As per my preferences, I wish the X9K cables were a little lighter, and may investigate alternatives down the line, but it's a very minor quibble.

The X9K exhibits superior fit and finish and quality materials throughout. The one issue I had was one of the head strap detents sometimes not holding firm when moderate pressure was applied to the nearby ear cup. As detailed in the dedicated X9K thread, I was able to fix this with a bit of effort.

X9000 Sound Impressions

To give context, a brief recap of my musical and sonic preferences:

• Favorite musical genres include rock (progressive to punk and most everything in-between), jazz, electronica/downtempo, and (instrumental) classical music
• Occasionally listened to genres include industrial, hip hop, and ambient/new age
• Rarely listened to genres include country, opera, and heavy metal
• Strong preference for headphones that are competent with any genre and don't require EQ
• Strong preference for headphones with excellent soundstaging and bass response

I have owned a Susvara for about three years, and have listened to it almost exclusively during that time (when not listening to my Vandersteen Treo CT speakers). Late last year, I acquired my first estat, the Hifiman Shangri-la Junior. While I was smitten with the SGL Jr's amazing speed, clarity, and soundstaging prowess, its early roll-off in the bass kept it from supplanting the Susvara as my daily driver. Technicalities aside, the ultimate utility of any headphone is its ability to convey music in a convincing and emotionally involving manner. When the bass is noticeably lacking, a lot of music sounds uninvolving to me. A bit of extra resolution and/or a better soundstage isn't enough compensation for anemic bass for me.

For the above reasons, the SGL Jr. has become only an occasional listen for me, and mostly with classical music or jazz. Comparatively, the X9K has been a revelation in terms of estat bass, arguably the best I've heard overall from an estat. (Please keep in mind that my knowledge of and experience with (particularly vintage) estats is dwarfed by many other Head-Fi members!) The exact quality and impact of the X9K bass seems to vary a fair bit depending on the track, but I think I've got a decent handle on it at this point. It's a very articulate and nuanced bass, but with excellent presence. It doesn't extend quite as far down as the Susvara bass, but the midbass is typically a bit more forward by comparison, which works very well for a lot of music. The X9K bass can sometimes have a slight quality of ripeness, but it doesn't bleed into the mids, and I generally find it very pleasing on most tracks. That said, I'd probably still take the Susvara bass if forced to choose between one or the other. Last night, my listening was focused largely on rock music. For my taste, the Susvara clearly bested the X9K on the following records: Murmur (R.E.M.), The Best of the Smithereens, Morningwood (Morningwood). I'm not sure exactly how much head time the X9K will get going forward vs. Susvara, but the latter will continue earning its keep for listening to material such as the above. I should note that for a lot of rock music, the X9K is a great headphone, and a highly enjoyable listen. I'm still qualifying that, but rock records where the bass is mixed lower play to the X9K's strengths a bit more. Interestingly, on bassy electronic/trip hop material, I often find the X9K more enjoyable than the Susvara. Examples I've listened to recently would be Becoming X (Sneaker Pimps) or Legion of Boom (The Crystal Method).

If I never listened to rock, I would rate the X9K more highly than the Susvara both on technical performance and overall sonic presentation. Let's now look at other attributes of the X9K vs. Susvara. My main sonic priorities in a headphone are accurate timbre/tonality, excellent soundstage, and resolution/detail retrieval. I would put the X9K roughly on par with the Susvara in terms of tonality/timbre. If the Susvara were rated (arbitrarily) 100 for timbre, I would assign the X9K at least a 97. I don't feel any need to EQ the X9K other than a 2-3 dB bass shelf on some music, and it doesn't have any obvious weaknesses at any point in the frequency spectrum. Instruments and vocals sound quite true to life on the X9K, although its presentation can be a tad more ethereal and saturated than the Susvara's on some tracks, which makes the Susvara sound just a bit more like live music at times. In terms of resolution and detail, the X9K is the clear winner vs. the Susvara. It's simple physics: more force applied to a lighter diaphragm equals more control, hence resolution of detail. The Susvara is probably the most resolving planar I've heard (which is most of them), but the X9K simply lets you hear more of the harmonic and rhythmic nuances in the music. As an aside, some listeners/reviewers speak of a dichotomy between resolution and musicality, but I've never heard it that way. That would be like saying that a 4K TV would be at a disadvantage in rendering beautiful scenery vs. a lower resolution screen. In any case, if you enjoy highly resolving transducers, and have good components in your chain, the X9K will positively delight you with its ability to effortlessly present detail and ambience in a natural way.

Moving on, for my money the X9K reigns supreme in terms of soundstage, and that's in comparison to everything I've heard, not just the Susvara. Note that it's been some months since I heard the Shangri-la Sr., which might be on par (or even better). The X9K's soundstage is vast in width and depth, with sublime precision and coherence. Interestingly, the Susvara images instruments just a bit more precisely, and the space between instruments is blacker. On the X9K, instruments are subjectively slightly larger and a hair more diffuse in the soundstage. Both presentations are exceptional, and which is "better" might come down to individual tracks. For something with a lot of instrument panning or effects moving through the soundstage, I'd take the X9K 100% of the time. The Susvara would possibly be my preference for an intimate live recording, although the X9K soundstage is glorious with pretty much everything.

In summary, the X9K is a sensational headphone, and it clearly bests the Susvara (IMO) in a number of ways, particularly for genres outside of rock. The X9K is currently the headphone I reach for by default. My impressions of the X9K are still evolving, and I plan to update this thread over time with any salient new insights. Meanwhile, I'll be happy to answer any questions, or take any requests for tracks you'd like me to A/B on the X9K vs. Susvara.

 

[tunes]

Have you heard the Susvara paired with the ENLUEM 23 or a great tube amp?

 

[eskamobob1]

Have you heard the Susvara paired with the ENLUEM 23 or a great tube amp?

His primary setup runs sus fully. I also concur with him though that the bass of x9k is damned close to sus. The only thing is sus bass has slightly more body and slightly more slam dispite losing significantly in speed. I realy think the real thing here is how well sus does sub-bass tactility. Like you can litteraly feel the rumble in your ear drums even if you can't always here it. X9k doesn't seem to have quite enough force to do that. Tbh sus is one of only 3 cans i feel truly beat x9k at bass (sus, 1266, d8kp, but maybe valkyria would as well i just haven't heard it).

 

[BassicScience]

EKSONIC AERAS REVIEW

Thanks to the kind generosity of @Kerry , the proprietor of Eksonic, I was able to home demo the Eksonic Aeras estat amp for the past month. I was able to listen fairly extensively to the Aeras in comparison to my NAD/iESL setup, with both my recently purchased STAX SR-X9000, as well as with the STAX SR-009S, which I had purchased a couple of months ago as a stopgap until my X9K arrived.

To facilitate easy comparisons between the Aeras and the iESL, I simultaneously used both the RCA and XLR outputs from my reference DAC, the EMM Labs DA2 V2. I also inserted my Benchmark DAC3 into the chain before the Aeras to convert RCA (DAC output) to XLR (Aeras input), as well as to provide remote control of volume and muting. The DAC3 is a middling DAC in my opinion, but its preamp section is quite superb and very transparent based on critical A/B testing I've done in the past. That said, the Aeras arguably would have sounded even better with a direct XLR connection from my EMM Labs DAC. For completeness, here are the respective chains used in my listening sessions:

DA2 V2 DAC (XLR) ---> Audio Research Ref 6SE Preamp (XLR) ---> NAD M22 V2 ---> iFi iESL Energizer ---> Estat headphone

DA2 V2 DAC (RCA) ---> Benchmark DAC3 (RCA analog in, XLR out) ---> Eksonic Aeras ---> Estat headphone

=========

Before discussing sonic impressions, herewith a brief digression on the ergonomics of the Aeras amplifier. The Aeras represents trickle-down technology from the universally highly acclaimed Eksonic DIY T2 estat amp, in a much smaller form factor and at roughly half the cost. The Aeras features a single (rear) XLR input and a single STAX Pro-Bias headphone jack. There is also a large volume knob and a power switch with a ring LED on the front panel. The volume is not controllable remotely. After being switched ON, the Aeras enters standby (muted) mode, indicated by the power LED flashing, as well as a handful of red LEDs illuminating near the front of the complement of four (4) 6S4A tubes socketed atop the amp. After perhaps 30-45 seconds (I never timed it), the Aeras comes out of standby (and unmutes), indicated by the power LED transitioning from flashing to solid ON, as well as another dozen or so red LEDs illuminating throughout the region of the tube sockets. Operation was extremely straightforward, and I encountered no glitches whatsoever during my month of use.

Aesthetics are subjective, but I find the Aeras to be a very attractive piece of gear. There is an elegance, not to mention tremendous practicality, in its compact form factor. Fit and finish are exceptional. There are no sharp edges on the heat sinks or elsewhere, and the matte finish to the metalwork is beautiful. The Aeras would be a top choice for an estat amp to fit on a desk or bedside table, or to take on the road.

I should note that the Aeras operates in class A and gets very warm. Several seasoned estat folks have pointed out that this is true of virtually all the well-known estat amps, whether tube or solid state. The Aeras may be slightly disadvantaged in dissipating heat due to its smaller form factor. Even though we live near the coast and don't have A/C in our house, the heat from the Aeras didn't noticeably affect ambient room temperature. My only minor niggle was that the front panel and volume knob also got rather warm to the touch after a period of continuous operation. I did mention this to Kerry, and he told me it may be possible to improve thermal isolation of the volume knob, but probably not the front panel. Since I was controlling volume remotely, I really only noticed this when plugging/unplugging a headphone, and it wouldn't be a deal-breaker for me in any case.

Sonic Impressions

The Aeras arrived prior to the STAX SR-X9000, so my initial evaluation was done using the STAX SR-009S (and briefly, the Hifiman Shangri-la Junior). I'd had the 009S for maybe a week prior to the arrival of the Aeras, so I'd formed an initial impression of the headphone driven from my iESL. Generally, I really liked what I was hearing from that combo. Bass was definitely elevated compared to my Shang Junior, and the timbre was more realistic than I'd remembered it from other auditions, typically on the BHSE. The technical proficiency of the 009S is high, if not quite state-of-the-art, and it exhibits most of the virtues of the better estats, while committing no overt sins of any real consequence. I found the tuning of the 009S through the NAD/iESL combo to work well for virtually all genres of music.

So what were the differences when moving the 009S over to the Aeras? In a nutshell, the Aeras served up an increase in treble energy. The subjective results of that were better depth and layering of the soundstage (with maybe a slight decrease in width), more shimmer and air around cymbals, and an increased vibrancy/glow to the music overall. I hadn't felt like something was missing with the iESL chain, but once I moved to the Aeras, music just sounded more energized and lifelike. The only downside of the Aeras/009S pairing was that the occasional recording exhibited a bit of heat or glare in the treble. I'd sometimes noticed this before with the BHSE/009S pairing, and I'd mostly attribute it to the 009S, as it was never an issue with the Aeras later driving the X9K. It's also highly likely the issue could be addressed via EQ, but I didn't bother to experiment with it since I knew the X9K was on the way at that point.

After the X9K arrived, I really didn't listen to the 009S anymore. As expected, the X9K also exhibited a bit more treble energy when driven by the Aeras vs. the NAD/iESL. Subjectively, however, the differences between the amps weren't as prominent when listening to the X9K. There was still an increase in soundstage depth/layering with the Aeras, and a bit more shimmer/air around cymbals, but the baseline established by the NAD/iESL/X9K combo was so excellent that the improvements from the Aeras seemed more incremental than they had with the 009S. I still think a majority of listeners would prefer the Aeras (as do I, in general), especially those who find the X9K a tad reticent in the treble region. There were occasions where I felt the iESL chain had a bit tighter grip on the bass than did the Aeras, but it was close enough that I couldn't say for sure. I will also note that when I listened to either amp for a period without switching, my ears seemed to adapt, and I was able to just normalize and enjoy whatever I was hearing at the moment. One takeaway from this experience was that the NAD/iESL is not a second rate option for driving estats by any measure. It may not be at the top of the mountain, but it's within shouting distance. Of course, I've only heard the Eksonic DIY T2 briefly at CanJam, and not with the X9K, so the gap may in fact be much wider than I'm imagining.

Bottom line: I would recommend the Eksonic Aeras without reservation! Paired with the STAX SR-X9000, the sound quality was nothing short of spectacular. The Aeras also sounded fantastic with the STAX SR-009S. The only headphone which I preferred driven by the iESL was the Hifiman Shangri-la Junior. It's a rather bright estat to begin with, and it had better synergy with the iESL chain to my ears.

As always, one listener's subjective opinion. YMMV.

=============

FOLLOW-UP FROM EKSONIC (11 August 2022)

I received the following message today from @Kerry of Eksonic, reprinted in its entirety:

I got the Aeras back yesterday. It turns out that the heatsinks on it were from an earlier version and they run about 8-10 degrees F hotter than the current production. That explains why they felt hot to you - because they were. I didn't remember that the one I sent to @number1sixerfan had the older heatsinks. The electronics are the same in both.

[Editor's NOTE: My Aeras demo unit had originally been sent to @number1sixerfan several months ago, and I received it directly from him.]

The photo below shows the difference. I spent a bunch of time designing the new front heat sinks (right) vs the earlier off-the-shelf heat sinks (left). The larger spacing really helped.

You can also see that the finish is a bit different too. The newer one is a semi-gloss anodized (top/bottom/back) vs the flat anodized that you had.

 

[BassicScience]

Have you heard the Susvara paired with the ENLUEM 23 or a great tube amp?

I heard the Enleum 23 driving the Susvara at CanJam about a year ago, but only for 15 minutes or less. I was very impressed by the pairing, as it gave the Susvara an ethereal, billowy soundstage that I found quite pleasurable to listen to. It didn't seem to be the most linear amp, but that clearly wasn't what the designer was going for. How that would hold up for me over time and with a wide variety of music, I don't really know. A lot of people do love that amp driving the Susvara, though. It seems somewhat overpriced to me unless you need a really small amp or just love that particular sound.

As to the second part of the question: no, but I've heard Susvara driven by a great tube preamp, and the results are spectacular!

In any case, this isn't really the thread to discuss Susvara pairings further.

 

[BassicScience]

His primary setup runs sus fully. I also concur with him though that the bass of x9k is damned close to sus. The only thing is sus bass has slightly more body and slightly more slam dispite losing significantly in speed. I realy think the real thing here is how well sus does sub-bass tactility. Like you can litteraly feel the rumble in your ear drums even if you can't always here it. X9k doesn't seem to have quite enough force to do that. Tbh sus is one of only 3 cans i feel truly beat x9k at bass (sus, 1266, d8kp, but maybe valkyria would as well i just haven't heard it).

I agree with most of what you say here, but my perception is that the Susvara bass is not really slower than the X9K's. At times I may even have felt the opposite, but again it tends to be very dependent on the specific track. I wonder if this can simply be explained by your driving the Sus with a tube amp, which generally has a lower damping factor? I guess you also use the Bakoon, which is SS, although I don't know its output impedance/damping factor.

 

[Gazza]

EKSONIC AERAS REVIEW

Thanks to the kind generosity of @Kerry , the proprietor of Eksonic, I was able to home demo the Eksonic Aeras estat amp for the past month. I was able to listen fairly extensively to the Aeras in comparison to my NAD/iESL setup, with both my recently purchased STAX SR-X9000, as well as with the STAX SR-009S, which I had purchased a couple of months ago as a stopgap until my X9K arrived.

To facilitate easy comparisons between the Aeras and the iESL, I simultaneously used both the RCA and XLR outputs from my reference DAC, the EMM Labs DA2 V2. I also inserted my Benchmark DAC3 into the chain before the Aeras to convert RCA (DAC output) to XLR (Aeras input), as well as to provide remote control of volume and muting. The DAC3 is a middling DAC in my opinion, but its preamp section is quite superb and very transparent based on critical A/B testing I've done in the past. That said, the Aeras arguably would have sounded even better with a direct XLR connection from my EMM Labs DAC. For completeness, here are the respective chains used in my listening sessions:

DA2 V2 DAC (XLR) ---> Audio Research Ref 6SE Preamp (XLR) ---> NAD M22 V2 ---> iFi iESL Energizer ---> Estat headphone

DA2 V2 DAC (RCA) ---> Benchmark DAC3 (RCA analog in, XLR out) ---> Eksonic Aeras ---> Estat headphone

=========

Before discussing sonic impressions, herewith a brief digression on the ergonomics of the Aeras amplifier. The Aeras represents trickle-down technology from the universally highly acclaimed Eksonic DIY T2 estat amp, in a much smaller form factor and at roughly half the cost. The Aeras features a single (rear) XLR input and a single STAX Pro-Bias headphone jack. There is also a large volume knob and a power switch with a ring LED on the front panel. The volume is not controllable remotely. After being switched ON, the Aeras enters standby (muted) mode, indicated by the power LED flashing, as well as a handful of red LEDs illuminating near the front of the complement of four (4) 6S4A tubes socketed atop the amp. After perhaps 30-45 seconds (I never timed it), the Aeras comes out of standby (and unmutes), indicated by the power LED transitioning from flashing to solid ON, as well as another dozen or so red LEDs illuminating throughout the region of the tube sockets. Operation was extremely straightforward, and I encountered no glitches whatsoever during my month of use.

Aesthetics are subjective, but I find the Aeras to be a very attractive piece of gear. There is an elegance, not to mention tremendous practicality, in its compact form factor. Fit and finish are exceptional. There are no sharp edges on the heat sinks or elsewhere, and the matte finish to the metalwork is beautiful. The Aeras would be a top choice for an estat amp to fit on a desk or bedside table, or to take on the road.

I should note that the Aeras operates in class A and gets very warm. Several seasoned estat folks have pointed out that this is true of virtually all the well-known estat amps, whether tube or solid state. The Aeras may be slightly disadvantaged in dissipating heat due to its smaller form factor. Even though we live near the coast and don't have A/C in our house, the heat from the Aeras didn't noticeably affect ambient room temperature. My only minor niggle was that the front panel and volume knob also got rather warm to the touch after a period of continuous operation. I did mention this to Kerry, and he told me it may be possible to improve thermal isolation of the volume knob, but probably not the front panel. Since I was controlling volume remotely, I really only noticed this when plugging/unplugging a headphone, and it wouldn't be a deal-breaker for me in any case.

Sonic Impressions

The Aeras arrived prior to the STAX SR-X9000, so my initial evaluation was done using the STAX SR-009S (and briefly, the Hifiman Shangri-la Junior). I'd had the 009S for maybe a week prior to the arrival of the Aeras, so I'd formed an initial impression of the headphone driven from my iESL. Generally, I really liked what I was hearing from that combo. Bass was definitely elevated compared to my Shang Junior, and the timbre was more realistic than I'd remembered it from other auditions, typically on the BHSE. The technical proficiency of the 009S is high, if not quite state-of-the-art, and it exhibits most of the virtues of the better estats, while committing no overt sins of any real consequence. I found the tuning of the 009S through the NAD/iESL combo to work well for virtually all genres of music.

So what were the differences when moving the 009S over to the Aeras? In a nutshell, the Aeras served up an increase in treble energy. The subjective results of that were better depth and layering of the soundstage (with maybe a slight decrease in width), more shimmer and air around cymbals, and an increased vibrancy/glow to the music overall. I hadn't felt like something was missing with the iESL chain, but once I moved to the Aeras, music just sounded more energized and lifelike. The only downside of the Aeras/009S pairing was that the occasional recording exhibited a bit of heat or glare in the treble. I'd sometimes noticed this before with the BHSE/009S pairing, and I'd mostly attribute it to the 009S, as it was never an issue with the Aeras later driving the X9K. It's also highly likely the issue could be addressed via EQ, but I didn't bother to experiment with it since I knew the X9K was on the way at that point.

After the X9K arrived, I really didn't listen to the 009S anymore. As expected, the X9K also exhibited a bit more treble energy when driven by the Aeras vs. the NAD/iESL. Subjectively, however, the differences between the amps weren't as prominent when listening to the X9K. There was still an increase in soundstage depth/layering with the Aeras, and a bit more shimmer/air around cymbals, but the baseline established by the NAD/iESL/X9K combo was so excellent that the improvements from the Aeras seemed more incremental than they had with the 009S. I still think a majority of listeners would prefer the Aeras (as do I, in general), especially those who find the X9K a tad reticent in the treble region. There were occasions where I felt the iESL chain had a bit tighter grip on the bass than did the Aeras, but it was close enough that I couldn't say for sure. I will also note that when I listened to either amp for a period without switching, my ears seemed to adapt, and I was able to just normalize and enjoy whatever I was hearing at the moment. One takeaway from this experience was that the NAD/iESL is not a second rate option for driving estats by any measure. It may not be at the top of the mountain, but it's within shouting distance. Of course, I've only heard the Eksonic DIY T2 briefly at CanJam, and not with the X9K, so the gap may in fact be much wider than I'm imagining.

Bottom line: I would recommend the Eksonic Aeras without reservation! Paired with the STAX SR-X9000, the sound quality was nothing short of spectacular. The Aeras also sounded fantastic with the STAX SR-009S. The only headphone which I preferred driven by the iESL was the Hifiman Shangri-la Junior. It's a rather bright estat to begin with, and it had better synergy with the iESL chain to my ears.

As always, one listener's subjective opinion. YMMV.

Thanks for the detailed write-up. Like you I'm utilising an energizer to run my STAX (009) with my existing pre and power (see sig). While not as rarified as your chain I figured taking advantage of existing amps would (hopefully) get me close to a high quality dedicated electrostatic amp that would be better than my weak STAX SRM-007tII.

Reading your impressions it seems that while there are advantages in buying a high-quality dedicated 'stats amp the marginal gains are not worth the outlay vs sticking with the energizer.