iFi Audio Pro iESL - The Official Thread

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  1. Muinarc
    Don't be afraid of the impedance knob, set it to where you can get the volume you want. turn the iCan Pro's volume down all the way, turn the impedance knob to any setting, then turn up the iCan slowly. If it gets too loud, too fast, then go to a higher impedance setting and try again. The goal on most audio gear is to have your "normal listening" volume be straight up at 12 o'clock on the volume knob where most potentiometers are at their most accurate.

    I am testing an iESL right now and using a 200W amp and Stax 007. To have play in the preamp (volume control) I need to use either the 64 or 96ohm setting. 580V bias and "pro" setting on the AC Termination. This is with balanced connections which are almost 5V in my system so there's already less headroom. I can double my volume spread if I use single ended between the gear.
  2. paolin

    With the 200+200W + iESL and 007 is the result better or not compared to a Stax or other headphone amplifier ?
  3. Khragon
    Thanks for the tip, couple more clarifications:
    The manual isn't very clear, but looks like the SR-007A has a 5-pin connection, so that will use the Custom/Pro jack.

    I assumed that means it will need at least 500V bias? and from the manual 580V for the SR-007A? can I use anything below that?
    Also AC termination looks like need to be set to Pro only?

    Sorry for the newbie questions as this will be my first experience with electrostatic and the iESL.

  4. Muinarc
    All Stax sold in like the past 30+ years are Pro bias and 580V. You would want to use that setting. I believe it is ok to go lower but that is outside of what the manufacturer designed the headphones for so I would expect worse performance at lower settings, if you go higher you risk burning holes in the diaphragm by arcing between the stators with too much voltage.

    The AC termination can be played with, from what the manual says I don't believe you can hurt anything with any of the settings.
  5. Rayzilla
    I look forward to your review. Will you be posting it here or in a separate thread?
  6. analogsurviver
    I have yet to decide. Review is half - or so - made, some measurements still have to be taken - and I might have to start using ARTA software in order to present some graphs ; not exactly something I am fond of learning during otherwise very busy time of the year.

    Even If I decide to post the finished review in a separate thread, I will at least post link to that thread here.
    Last edited: Nov 27, 2017
    Rayzilla likes this.
  7. iFi audio
    We would recommend to keep the impedance setting at 64 ohms and bias at the standard 580V as a starting point. Initially switch off "AC Termination".

    It is possible to lower bias below 580V, this reduces maximum SPL but tends to alter tonal balance some.

    If the sound levels are percived very low, 24 or 16 ohm impedance settings can be tried.

    However, either 24 or 16 ohm setting may produce much higher signal voltages than designed for by Stax, so being careful with the volume control and X-Bass is recommended.
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  8. paolin

    Sorry, i did not understand : why to select "AC termination" on off instead on pro if i select on "bias" 580v ?
  9. iFi audio
    If possible, please send us a PM regarding test Setup used to measure. Some Background on how to measure devices like the iESL you might find useful:

    Electrostatic headphones (common types) are in effect a capacitor of around 120pF capaitance and in effect close to infinite DC resistance and floating (not ground referenced) loads. Signal voltages can reach up to 640V RMS (if using iCAN Pro to drive).

    Any measurement system must:
    • approximate this kind of load
    • be floating
    • be calibrated to offer a flat measured frequency response under those conditions
    Normal sound card Inputs, even with voltage dividers and the standard input on audio analysers are entierly unsuitable as they will not produce a flat frequency response.

    To the best of our knowledge, no suitable systems exist readily obtainable. And it took serious effort to produce our own to use in conjunction with our Audio Precision System 2.
    iFi audio Stay updated on iFi audio at their sponsor page on Head-Fi.
  10. BadBoy
    I'm also wondering why to select "AC terminiation" on off instead on pro or pro*normal? and what's difference between 'pro' and 'pro normal'?
  11. Khragon
    I am curious to learn more about the AC termination feature as well. The manual states that AC termination affects 3D sound stage. Can someone help elaborate on how this is done beyond what is in the manual.

    @BadBoy, I think the AC switch is to enable the feature for certain output jack, Pro means only for Pro jack, Pro Normal is for both.
  12. Khragon
    Last edited: Dec 3, 2017
  13. Slim1970
    Having an issue with my Pro iESL. On power up the light is staying green and never switching to orange.
  14. iFi audio
    That 'orange' was a typo in the manual. Green is good.
    iFi audio Stay updated on iFi audio at their sponsor page on Head-Fi.
  15. Slim1970
    Thanks for the reply. I've been in contact with iFi support and they said they are going to update the manual. But I'm having a big issue with hum. They is a considerable amount of hum coming from the amp when I plug my Stax headphones in. This can't be normal because it there when there's no music playing and I can hear it when music is playing as well. I'm waiting on a response from iFi support on the issue.
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