[analogsurviver]

Regarding setting the impedance selector it should be noted that iFi Pro iESL has, efectively, as far as the gain is concerned, only two significantly different setings; those for 96 and 68 ohm - and those for 24 and 16 ohm. The difference between the first and second group in gain is just below 6 dB - which is significant ( almost double as loud ) .

DO NOT switch from 96/64 to 24/16 ohms while music is playing loud - in case of a more powerful amplifier, damage to headphones may result. Reduce the volume setting by at least 6 dB prior switching impedance from 96/68 to 24/16 ohm setting.
Switching in reverse direction will only result in lower output level, no danger to headphones even if you play loudly without reducing the level.

The differences in output level/gain between the 96 and 64 ohm is barely audible 0.2 dB or so - about the same for the difference between 24 and 16 ohm. The changes in level are not significant, something that can not be said about the resulting frequency response, where the differences are audible. Furthermore, the level of distortion in the low frequency range, which happens due to magnetic saturation, is significantly better with high imedance settings . Ultimately, it is the combination of amplifier and your ears/preferences in music/sound which will decide which setting will be most enjoyable by the end user.

More about this in my forthcoming , long ovedue review of this extraordinarily interesting "transformer". I have to decide which of the ( too numerous) measurements should be presented - in comparison to Stax SRM1MK2 amplifier, both Pro iESL and Stax driving a single pair of Stax Lambda Pro.

Stay tuned !

 

[iFi audio]

Great! With luck I'll get to try it by the weekend!"

Do let us know how you get on.

 

[gordec]

I can't find any info on this looking through all the threads. I have a McIntosh MHA100 amp. Can I feed the IESL through speaker taps and use the IESL without the iCan Pro?

 

[Slim1970]

I can't find any info on this looking through all the threads. I have a McIntosh MHA100 amp. Can I feed the IESL through speaker taps and use the IESL without the iCan Pro?

Yes, just hook your amp to the speaker taps and change the input to “speaker” and you’re in business.

 

[iFi audio]

Yes, just hook your amp to the speaker taps and change the input to “speaker” and you’re in business.

 

[gordec]

Sweet. This means I can just get the IESL and still use my McIntosh amp for electrostats. Question is how will it sound.

 

[iFi audio]

Sweet. This means I can just get the IESL and still use my McIntosh amp for electrostats. Question is how will it sound.

A good question indeed. Please feel free to let us know somewhere in the future and enjoy!

 

[Rayzilla]

... More about this in my forthcoming , long ovedue review of this extraordinarily interesting "transformer". I have to decide which of the ( too numerous) measurements should be presented - in comparison to Stax SRM1MK2 amplifier, both Pro iESL and Stax driving a single pair of Stax Lambda Pro.

Stay tuned !

Still impatiently waiting ....

 

[kid vic]

@iFi audio I know you guys take pride in your products and put significant time and effort into designing them using thorough research as your base; with that in mind I would like to hear you directly speak about the sentiments expressed in this post: https://www.head-case.org/forums/topic/786-the-headcase-stax-thread/?do=findComment&comment=778245

For the record the only reason i ask is because some of the people active in that thread (as well as the poster of the statement I've linked) are well respected here on head-fi as well as on other sites as the authorities on all things stax. For better or for worse a lot of people differ to their experience and knowledge so I would greatly appreciate you addressing their claims.

 

[iFi audio]

@iFi audio I know you guys take pride in your products and put significant time and effort into designing them using thorough research as your base; with that in mind I would like to hear you directly speak about the sentiments expressed in this post: https://www.head-case.org/forums/topic/786-the-headcase-stax-thread/?do=findComment&comment=778245

For the record the only reason i ask is because some of the people active in that thread (as well as the poster of the statement I've linked) are well respected here on head-fi as well as on other sites as the authorities on all things stax. For better or for worse a lot of people differ to their experience and knowledge so I would greatly appreciate you addressing their claims.

There are many things factually inaccurate in this post. It is combined with a lot of talk about things the poster admits he does not know (though we do) and other show his rather debatable understanding of basic electronics.

He is of course entitled to his opinion and choice, which is perfectly fine in our book, though the language used is a trifle too colorful to our taste. We generally do not get ourselves involved in such cases.

As for the iESL 'not making any sound' and 'not working as amplifier', this product is not an amplifier and needs to be seen in the system context to be grasped properly. When combined with our Pro iCAN, the drive voltage to electrostatic headphones can be as high as 730V RMS, which is higher (and louder) than any other commercial amplifier out there.

Hence our recommendation would be to have a listen without being prejudiced and letting the results speak for themselves.

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

If we were to address some of the points:

• The transformers inside Pro iESL were designed for the job they do and took dozens of prototypes to optimise after the initial design, which naturally took all relevant parameters into account.

• We achieve in practice > 60kHz bandwidth measured in the actual system with Stax SR-009 connected to the Pro iESL driven via Pro iCAN.

• The bias system operates EXACTLY as we describe in our literature; it leaves in effect a floating capacitor bank charged to the required voltage and topped up when needed.

• The transformers that generate high voltage and their drivers' ICs are in plain sight. We just prefer to use 21st century technology where appropriate, thus the circuit parts involved are VERY small.

• The bias voltage adjustment is naturally made in the control section for the actual step-up circuit, which handles charging the capacitor bank to required voltage and operates as low voltage, at around 1.2V to be precise.

• As for AC termination or the bias circuit, many amplifiers designed for electrostatic speakers, the biggest names in the business have it, others do not.

• We give a user the choice to either use AC termination or not. Without it there is a significant (unwanted) LF crosstalk, which has its own consequences for what is heard.

 

[kid vic]

There are many things factually inaccurate in this post. It is combined with a lot of talk about things the poster admits he does not know (though we do) and other show his rather debatable understanding of basic electronics.

He is of course entitled to his opinion and choice, which is perfectly fine in our book, though the language used is a trifle too colorful to our taste. We generally do not get ourselves involved in such cases.

As for the iESL 'not making any sound' and 'not working as amplifier', this product is not an amplifier and needs to be seen in the system context to be grasped properly. When combined with our Pro iCAN, the drive voltage to electrostatic headphones can be as high as 730V RMS, which is higher (and louder) than any other commercial amplifier out there.

Hence our recommendation would be to have a listen without being prejudiced and letting the results speak for themselves.

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

If we were to address some of the points:

• The transformers inside Pro iESL were designed for the job they do and took dozens of prototypes to optimise after the initial design, which naturally took all relevant parameters into account.

• We achieve in practice > 60kHz bandwidth measured in the actual system with Stax SR-009 connected to the Pro iESL driven via Pro iCAN.

• The bias system operates EXACTLY as we describe in our literature; it leaves in effect a floating capacitor bank charged to the required voltage and topped up when needed.

• The transformers that generate high voltage and their drivers' ICs are in plain sight. We just prefer to use 21st century technology where appropriate, thus the circuit parts involved are VERY small.

• The bias voltage adjustment is naturally made in the control section for the actual step-up circuit, which handles charging the capacitor bank to required voltage and operates as low voltage, at around 1.2V to be precise.

• As for AC termination or the bias circuit, many amplifiers designed for electrostatic speakers, the biggest names in the business have it, others do not.

• We give a user the choice to either use AC termination or not. Without it there is a significant (unwanted) LF crosstalk, which has its own consequences for what is heard.

Thank you for your well tempered response. I hope that anyone else interested in this product will see your rebuttal and be willing to give it a shot .

 

[Zblarg]

I'm not a technician and can't speak about the headphones safety when plugged into the IESL.
But I recently bought an Ifi IESL for my 007 and my 009. I already own a KGSSHV Carbon CC which is a marvellous amplifier and it's evident to me that Birgir knows very well his job.
The Ifi IESL's performance clearly depends on what you're using in connection with it.
I connected the IESL in the first time to my Viva Egoista 845 headphone tube amplifier, and I was blown away by the sound with my 007 and my 009. Big soundstage, superb midrange, perfect treble...
The 009 especially, which I always found too bright and thin, even with the Carbon (I think the Carbon generally has a better synergy with the 007) simply comes to life. It's a tube amplifier so it has a different flavour.
Then I connected the IESL to my Pass Labs X0.2 preamp + Coda CX monoblocks (450 watts), which is a solid state system for speakers. Then it was also a really big surprise.
Quite different from the Viva, closer to the Carbon, but with more body, deeper bass, thicker midrange and a bit darker. This is, I think, the best sound I've ever heard from my 009.

From my expercience the IESL doesn't have a sound signature by itself. It provides the sound signature of the amplifier connected to it. I easily recognize the sound signature of my Viva and my Coda amps when I use them with my IESL.
Of course, the Pass + Coda combo costs about $20 000 so it's about four times the cost of a Carbon amplifier... It's a bit unfair. The Carbon is still a state of the art solid state amplifier. But here is the interesting thing with the IESL: if you already have a very high end system for dynamic headphones or for loudspeakers, you can keep it and make it compete with the best electrostatic amplifiers for a reasonable cost.

By the way, the IESL seems to have a very low efficiency, so I agree with the fact that you need a very powerful amplifier and you have to put a very high volume to get a satisfying volume with your Stax headphones (very, very high for the SR-007). But I don't see it as an issue. It's just power hungry, like many great things are.

I think this IESL deserves more attention. It's truly exceptionnal, and I guess it can easily be ruined if not connected to really good electronics.

 

[Rayzilla]

I'm not a technician and can't speak about the headphones safety when plugged into the IESL.
But I recently bought an Ifi IESL for my 007 and my 009. I already own a KGSSHV Carbon CC which is a marvellous amplifier and it's evident to me that Birgir knows very well his job.
The Ifi IESL's performance clearly depends on what you're using in connection with it.
I connected the IESL in the first time to my Viva Egoista 845 headphone tube amplifier, and I was blown away by the sound with my 007 and my 009. Big soundstage, superb midrange, perfect treble...
The 009 especially, which I always found too bright and thin, even with the Carbon (I think the Carbon generally has a better synergy with the 007) simply comes to life. It's a tube amplifier so it has a different flavour.
Then I connected the IESL to my Pass Labs X0.2 preamp + Coda CX monoblocks (450 watts), which is a solid state system for speakers. Then it was also a really big surprise.
Quite different from the Viva, closer to the Carbon, but with more body, deeper bass, thicker midrange and a bit darker. This is, I think, the best sound I've ever heard from my 009.

From my expercience the IESL doesn't have a sound signature by itself. It provides the sound signature of the amplifier connected to it. I easily recognize the sound signature of my Viva and my Coda amps when I use them with my IESL.
Of course, the Pass + Coda combo costs about $20 000 so it's about four times the cost of a Carbon amplifier... It's a bit unfair. The Carbon is still a state of the art solid state amplifier. But here is the interesting thing with the IESL: if you already have a very high end system for dynamic headphones or for loudspeakers, you can keep it and make it compete with the best electrostatic amplifiers for a reasonable cost.

By the way, the IESL seems to have a very low efficiency, so I agree with the fact that you need a very powerful amplifier and you have to put a very high volume to get a satisfying volume with your Stax headphones (very, very high for the SR-007). But I don't see it as an issue. It's just power hungry, like many great things are.

I think this IESL deserves more attention. It's truly exceptionnal, and I guess it can easily be ruined if not connected to really good electronics.

Thanks for putting the iESL through these tests and for providing your comments on this.

I would be interested to know how it would sound with the two amps that I already own: the Pro iCan and the Audio GD Master 9. I wish I was able to test it out somehow. I would appreciate it if anyone gets the chance to do this or test with any other amplifiers too.

 

[iFi audio]

I'm not a technician and can't speak about the headphones safety when plugged into the IESL.
But I recently bought an Ifi IESL for my 007 and my 009. I already own a KGSSHV Carbon CC which is a marvellous amplifier and it's evident to me that Birgir knows very well his job.
The Ifi IESL's performance clearly depends on what you're using in connection with it.
I connected the IESL in the first time to my Viva Egoista 845 headphone tube amplifier, and I was blown away by the sound with my 007 and my 009. Big soundstage, superb midrange, perfect treble...
The 009 especially, which I always found too bright and thin, even with the Carbon (I think the Carbon generally has a better synergy with the 007) simply comes to life. It's a tube amplifier so it has a different flavour.
Then I connected the IESL to my Pass Labs X0.2 preamp + Coda CX monoblocks (450 watts), which is a solid state system for speakers. Then it was also a really big surprise.
Quite different from the Viva, closer to the Carbon, but with more body, deeper bass, thicker midrange and a bit darker. This is, I think, the best sound I've ever heard from my 009.

From my expercience the IESL doesn't have a sound signature by itself. It provides the sound signature of the amplifier connected to it. I easily recognize the sound signature of my Viva and my Coda amps when I use them with my IESL.
Of course, the Pass + Coda combo costs about $20 000 so it's about four times the cost of a Carbon amplifier... It's a bit unfair. The Carbon is still a state of the art solid state amplifier. But here is the interesting thing with the IESL: if you already have a very high end system for dynamic headphones or for loudspeakers, you can keep it and make it compete with the best electrostatic amplifiers for a reasonable cost.

By the way, the IESL seems to have a very low efficiency, so I agree with the fact that you need a very powerful amplifier and you have to put a very high volume to get a satisfying volume with your Stax headphones (very, very high for the SR-007). But I don't see it as an issue. It's just power hungry, like many great things are.

I think this IESL deserves more attention. It's truly exceptionnal, and I guess it can easily be ruined if not connected to really good electronics.

Thanks for your feedback, well done! One rather major thing to address, though. Pro iESL is not an amplifier, its an energizer. Thus it's of great importance what amplifier feeds it.

 

[paolin]

Thanks for your feedback, well done! One rather major thing to address, though. Pro iESL is not an amplifier, its an energizer. Thus it's of great importance what amplifier feeds it.

Something that can rassue us about the headphones safety when plugged into the IESL ?