[BassicScience]

I have a feeling that you need to try a different amplifier. Try a high quality tube amp with better tubes if you have money for that. Also equalizing helps if not suited to your ears. I have modified my estat and equalized them to my liking. Sound is like earth is in space and you are looking at it from the space station. Hope that was not too confusing

The only thing that's confusing is why you're recommending a different amplifier when I said I am delighted with my current ones driving the Susvara, and haven't even heard them driving an e-stat through the iESL as yet. I don't like tube power amps for a number of reasons (which I won't enumerate here), particularly in a context where significant power is required, although I do have a SOTA tube preamp in the chain. I also prefer not to EQ. If a speaker or headphone isn't voiced to my liking, I generally just find a different one that is.

 

[iFi audio]

I wanted to say thanks to @BTD1 for the heads up about the iESL being discontinued. After hearing the Hifiman Shangri-la Junior at the recent CanJam, I was impressed enough to place an order for one a couple weeks ago, and it's currently being held up in US Customs. Since this will be my first e-stat, I needed to arrange amplification, and the iESL seemed to be a fantastic option. Since I already own a couple of powerful Class D amps (which I love driving my Susvara), I was loathe to spend kilobucks on a separate e-stat amp right out of the gate. The iESL is compact, versatile, and reasonably priced, so I ordered one before iFi even confirmed that it was discontinued, and was very fortunate to grab one of the last available units. It arrived a few days ago, and I have been listening to the Susvara through it until my Shang Jr. arrives (hopefully soon).

The iESL is a well-engineered piece of gear. It feels solid and the controls have a nice tactility. Connectors and binding posts are excellent quality as well. My only minor nits would be:

1. I could do without the orange "floodlighting" emanating from the top of the unit. It would also be nice to have a dimmer (and/or off switch) for the backlit iFi logo.
2. The lettering by the control knobs is hard to read in daylight, impossible in dim light.
3. The downside to the compactness of the unit is that the speaker connections are not well-spaced. I'm going to look into locking banana connectors in lieu of spades to mitigate this issue.

So how does it sound with the Susvara? I've been driving the iESL with my NAD M22 V2 on its lowest gain setting (19 dB). The 4-pin adapter that was hanging off the amp is now attached to the speaker outputs of the iESL, which allows me to easily compare the sound directly out of the NAD vs. through the transformer in the iESL. After playing around with the impedance options on the iESL, I settled on 24 ohms as my favorite both for its tonal profile and that its output level is roughly the same as bypassing the iESL. After a few nights of listening, I have to say that I'm very impressed with the transparency of the iESL. Clearly, the engineering that went into the transformer is paying dividends sonically. I'm not entirely sure I could pass a blind test between the Susvara directly from my NAD amp vs. with the iESL in the chain. I think listening through the iESL yields a slight increase in bass punch along with a very slight decrease in treble energy. The imaging may be just a tad more precise directly from the amp, giving the subjective impression that one is slightly farther from the stage. Which I prefer depends on the music being played and perhaps my mood. Again, these are not dramatic differences, which is good in my view. It's great to have the option to so conveniently use or bypass the iESL for non-estats. Also, for more sensitive headphones than the Susvara (basically everything), one can simply increase the impedance of the iESL and use a speaker amp to drive them.

I will update this thread when I receive the Shangri-la Junior regarding how it sounds out of the iESL. Based on listening to the Susvara, I'm rather optimistic that the Shang Jr. will also play well with the iESL. Unfortunately, the only amp comparison I will be able to offer in the short term is to the dedicated Hifiman amp for the Shang Jr., and that only from my memory of the CanJam system. In the next few months, I'll probably be able to compare the iESL to a BHSE and potentially other dedicated e-stat amps, and will certainly plan to report on those experiences here.

It really is a shame that the iESL has been discontinued! I hope iFi reconsiders or develops a successor, as there is definitely a strong niche for quality e-stat energizers, particularly with the recent emergence of several new TOTL e-stat headphones.

Thanks a lot for your feedback and we're happy to read that you like your iESL.

As for your comments:

1. A dimmer request is a fair point and I'll pass it on to our tech team.
2. Dark print on iESL was the best way to go ocnsidering its silver enclosure.
3. iESL had to have regular speaker taps and specific size typical for our Pro range, so considering this we couldn't make its rear panel any different. But yes, bananas will work best

 

[basisunus]

Finally I was able to try this combination. The AHB2 has been proposed to drive the iESL before but I never saw anyone did so. For a speaker amp, the AHB2 is usually not considered the most powerful. Its specs (100W to 8ohm) seem to match the requirements of the iESL perfectly. My first impression was that it doesn't overpower a pair of headphones at all. However, I had a better perception of the meaning of power: those high notes immediately sounded more effortless without turning up the volume. Both AHB2 and iESL are compact and run very cool. I think the heatsinks are unnecessary for such an application. I've so far tried Hifiman Jade 2 and Audeze Sine. I'm hoping to do some more comparisons with different inputs and headphones.

 

[h1f1add1cted]

Thanks for sharing and very nice enjoy! Really great to see, this is my dream power amplifier for the iESL, currently I'm on the budget performance solution with a Hypex Ncore NC252MP based power amplifier, but stunning to see this combo on a photo.

 

[iFi audio]

Finally I was able to try this combination. The AHB2 has been proposed to drive the iESL before but I never saw anyone did so. For a speaker amp, the AHB2 is usually not considered the most powerful. Its specs (100W to 8ohm) seem to match the requirements of the iESL perfectly. My first impression was that it doesn't overpower a pair of headphones at all. However, I had a better perception of the meaning of power: those high notes immediately sounded more effortless without turning up the volume. Both AHB2 and iESL are compact and run very cool. I think the heatsinks are unnecessary for such an application. I've so far tried Hifiman Jade 2 and Audeze Sine. I'm hoping to do some more comparisons with different inputs and headphones.

Thanks for your feedback and I'm happy to read that you like this combo. 100W into 8 ohms (...and probably twice that into 4 ohms) is more than most people might ever need. With speakers we rarely go above 5W

 

[analogsurviver]

I think your conclusions are wrong, Stax are driven by high voltage not current and this is biggest problem, as to play good they need peak to peak more than 1000V and very low current.
IESL use step transformers to drive Stax, what is needed is very fast amp, you don’t need high power.

Oh dear, here we go again. The most basic non understanding how ESLs work - they are electrically a capacitor.

A capacitor halves the impedance for every doubling the frequemcy - and for the infinite frequency response, you would need infinite power in order to charge this capacitance - BEFORE the voltage can be applied.

All said and done - for truly good ESL headphone performance, about 70 VA and above are required at its input terminals
- not just voltage.
Stax amps run ( roughly/average ) on 800 VDC power supply ( giving a 1600 V p-p ) and approx 5 mA idle current in class A - PER EACH of the four amps that together comprise "electrostatic amplifier". Two such amps in a bridge configuration are used per channel. The power output is approx 20-30 VA into the actual headphone driver.
The exact amount used in various models is left as an exercise to the reader - power consumption of the amp is a good starting point.

As such levels ( 70 VA and above ) already approach life treatening levels in terms of CURRENT at the required voltage, all Stax amps - even the most "badass" - are current limited in order to be able to get the CE approval. All amps exceeding these levels are banned in the EU; it is impossible to import - say - Beveridge 2SW speakers, which incorporate such amps.
KGHSV, BHSE et all hover JUST below the limits to remain on the legal side.

It IS possible to exceed the safety limits using iFi Pro iESL when it is powered off big enough amp. It CAN put out peaks exceeding 200 VA. That is a real concern if one is using analog records as a source - where a tick/pop/scratch most definitely CAN result in such outputs.
It can overvoltage/damage/destroy the majority of electrostatic drivers - with the exception of Jecklin Float, which operate normally with even higher voltages iESL can put out during peaks.
That is why the Quad Manufaktur "interface" for Jecklin Float is so expensive ... - and would be not only overkill, but dangerous to any other commercially available electrostatic headphones.

Sennheiser used in its Unipolar 2000 and 2002 Electret Headphones in its transformer input two back to back connected Zener dides in order to protect the ELECTRET headphone drivers from overload/arcing/destruction. Leaving a dead short as the load for the preceding amp ... - not something most amps are built with in mind.

Audio Technica did not use any voltage protection in their ATH6/7/8 series of electret headphones ... - and, in addition, had a 2:1 voltage ratio switch on the front panel of those "energizers" which are nothing but transformers. Many drivers fell prey to the irresistible desire to see what happens if one flicks that switch during playback from "LOW" to "HIGH" - in order to coax that last bit of anticipated "oomph". It did nothing but set one back for a pair of drivers - instantly.

So, try to educate yourself - and use common sense. Electrostatic headphone/trasnsformer/amplifier manufacturers are in fact misleading the prospective customers by quoting only the BIAS VOLTAGE/CURRENT as the only safety precaution - which really is of no concern, as it is usually connected trough a very large value resistor, which limits the current to really insignificant and totally harmless values.

They are quieter than a mouse regarding SIGNAL VOLTAGE/CURRENT ... - with which, the better the model , the closer to the lethal levels.

Like it or not - these are FACTS that no competent person can deny.

 

[BTD1]

So what should one take away from this discussion? I am new to the iESL and e-stats. I have the iESL and hope to purchase the CRBN when it's more available. Is there a risk of damaging the drivers in the Audeze CRBN by connecting them to the iESL and a speaker amp? I will use a Ragnarok 2 60 w/ch @ 8 ohms. Based on your knowledge of the voltage calculations, what is a safe amplifier power level such that damage to e-stat drivers is not likely to happen. What is a reasonable power level range from low to high? Now I have a new concern!

 

[jamesjames]

I'm very sorry to see the demise of the iESL, as I think it's the best thing to happen in the field of electrostatic drivers for a long time - even though the basic idea of using an additional outboard transformer to increase the voltage output of a conventional speaker amp is a very old idea! All electrostatic phones were originally driven this way. The iESL gives the user the opportunity to try a wide range of excellent amps with different features - not just the narrow range usually available to drive electrostatic headphones. My own preferred partner is the Moon 430HA - but there are many which I have found to give superb results - better than the conventional electrostatic drivers I've used with my Stax SR-009S phones (and I've used most). Those lucky enough to have an iESL might like to try experimenting with dedicated power supplies. The standard iPower is excellent I think - but I believe there is a subtle improvement with the iPower X, and a similar improvement again with the Sbooster (9 volt). The latter is a linear supply, but very quiet (as are all the iFi supplies).

 

[iFi audio]

Is there a risk of damaging the drivers in the Audeze CRBN by connecting them to the iESL and a speaker amp?

No. iESL was designed to allow these cans to work with regular speaker amps.

I'm very sorry to see the demise of the iESL, as I think it's the best thing to happen in the field of electrostatic drivers for a long time - even though the basic idea of using an additional outboard transformer to increase the voltage output of a conventional speaker amp is a very old idea!

The idea is old, but it all comes down to how it's implemented. E-stats are niche products so iESL, although successful, was nowhere near our top sellers. But who knows, perhaps one day we'll make an even better version of it.

 

[BassicScience]

I'm very sorry to see the demise of the iESL, as I think it's the best thing to happen in the field of electrostatic drivers for a long time - even though the basic idea of using an additional outboard transformer to increase the voltage output of a conventional speaker amp is a very old idea! All electrostatic phones were originally driven this way. The iESL gives the user the opportunity to try a wide range of excellent amps with different features - not just the narrow range usually available to drive electrostatic headphones. My own preferred partner is the Moon 430HA - but there are many which I have found to give superb results - better than the conventional electrostatic drivers I've used with my Stax SR-009S phones (and I've used most). Those lucky enough to have an iESL might like to try experimenting with dedicated power supplies. The standard iPower is excellent I think - but I believe there is a subtle improvement with the iPower X, and a similar improvement again with the Sbooster (9 volt). The latter is a linear supply, but very quiet (as are all the iFi supplies).

My understanding (someone correct me, if I'm wrong) is that the sole function of the power supply is to keep the capacitor bank at the desired bias voltage (nominally 580V). According to iFi, it recharges the capacitors every 30 seconds, typically for a period of microseconds. As such, I have a hard time believing that "upgrading" the power supply would be a worthwhile endeavor.

 

[deafenears]

The idea is old, but it all comes down to how it's implemented. E-stats are niche products so iESL, although successful, was nowhere near our top sellers. But who knows, perhaps one day we'll make an even better version of it.

Hopefully there is an iESL comeback, especially with the recent addition of Audeze's CRBN (in addition to HiFiMAN's Shangri-La Jr. and Jade)... more e-stats please.

 

[iFi audio]

Hopefully there is an iESL comeback, especially with the recent addition of Audeze's CRBN (in addition to HiFiMAN's Shangri-La Jr. and Jade)... more e-stats please.

It's good to know that folks are interested in iESL, I'll pass this on internally, thanks!

 

[ThanatosVI]

It's good to know that folks are interested in iESL, I'll pass this on internally, thanks!

Tell them to make it a better black Label Version please

 

[iFi audio]

Tell them to make it a better black Label Version please

That won't be easy considering how much work went into the first one

 

[jamesjames]

My understanding (someone correct me, if I'm wrong) is that the sole function of the power supply is to keep the capacitor bank at the desired bias voltage (nominally 580V). According to iFi, it recharges the capacitors every 30 seconds, typically for a period of microseconds. As such, I have a hard time believing that "upgrading" the power supply would be a worthwhile endeavor.

I'm also happy to stand corrected here - I had the other supplies on hand, and didn't really expect differences - but I think I do hear them. I take your point about the capacitor bank and power supply designed to maintain the bias voltage. But electrostatic phones also require a balanced signal pair for each channel, to support push-pull action on the diaphragm. Each of those signals must be at much higher voltages than the signals supplied to dynamic phones, and work into much higher impedances. My thinking had been the iESL has a role here also - but precisely how that works is beyond me!