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iFi - Pro iESL Electrostatic Amp (Open box)

Product SKU: Pro iESL


$1,349.10 Regular price $1,499.00 Save $149.90 (10% OFF)

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Product Details from the Brand

Electrostatic Headphone Transformer-Coupled Energiser

Pro iESL

Audio heaven.

Electrostatic headphones require sheer, raw power to drive their performance.

The Pro iESL energises your electrostatics. And then some.



Experience audio like never before.

Feel the energy.

Electrostatic headphones are the top of the range Porsches of the audio world, and the Pro iESL is the engine that drives them.

Unlike traditional amplifiers, the Pro iESL delivers the extra-high-tension voltage needed to energise the electrostatic plates in the headphones that produce ultimate musical nirvana.

Team iFi.

Coupled with the Pro iCAN, the Pro iESL lowers distortion, enhances and separates vocals, orchestras and instruments, opens the bass and leaves you with a wide, structured soundstage.

The ride of your life.

Paired with your beloved electrostatics, the Pro iESL amplifier takes you on a trip to audio heaven.

The tech spec.

The Pro iESL includes a:

  • Pinstripe Permalloy Core Transformer – To lower distortion,
  • Bias Voltage Generator – To charge electrostatics to the max before cutting them off to run on battery, not the mains so no electronic noise bleeds into the headset

The Pro iESL makes it virtually impossible for background noise and distortion to ruin your listening enjoyment.

Drive your electrostatics with one of the best energisers in the business. Compatible with all the great electrostatic headphone brands - including Orpheus and Koss.

The 'Perfectly Matched' headphone experience.

Both classic and cutting edge technology in 3 quality components delivers a perfectly matched listening experience - one-off Pinstripe Permalloy Core Transformer, a Bias Voltage Generator and the Capacitive Battery Power Supply.

Making a transformer with the wide bandwidth and low distortion needed in the iESL is very challenging. To attain this, the custom transformers use complicated hand-wound, multi-section windings with both vertical and horizontal sectioning.

They exceed the standards set by Siemans (Germany) and Peerless (USA). With a bandwidth of < 5Hz to > 60kHz (-3dB), transformers in the iESL far exceed the requirements of even the JAS High-Res Logo.

'The Capacitive Battery Power Supply.

The battery is charged up to the required voltage and then the charger circuit is turned off completely, leaving the capacitor bank to ‘float’ at the required bias voltage.

An essentially perfect bias voltage source with no electronic noise whatsoever at any frequency as the headphones are in essence, powered by the battery bank and not the mains!

These 1,000Volt rated capacitors are from Germany. The key is the very high insulation resistance and minimal current leakage, as any such leakage causes self-discharge.

The whole capacitor pack has around 35,000,000 kiloOhm insulation resistance, which means that self-discharge time (to 30%) is around 100,000 seconds or 27 hours. So one is always listening on battery (not mains) power.

Vishay MELF resistors - complex, costly BUT superior. These resistors provide optimal power rating and pulse load capability. Nothing else comes close.

Good news for your dynamics.

The unique transformer properties gives the iESL an ear tingling transformer coupled-stage that is unsurpassed. So each and every flagship dynamic headphone when used through the iESL enjoys a whole new level of smoothness and airiness.


Maximum Output voltage: 640V RMS (16?/20V in)
320V RMS (64?/20V in)
Frequency Response: 5Hz – 50kHz (-3dB)
Input Voltage (Pro iESL): 5V – 9V/1A max
Input Voltage (iPower): AC 85 – 265V, 50/60Hz
Power Consumption: < 1W
Dimensions: 213(l) x 206(w) x 63.3(h) mm
Weight: 2.5kg (5.5 lbs)

Product Reviews

iFi - Pro iESL Electrostatic Amp (Open box)

Customer Reviews
5.0 Based on 1 Reviews
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Mark H.
United States United States
Driving my SR-007 Mk2

I love the versatility of the iESL - I can run it with any amp I feel like owning. Right now, I've got my 007 Mk.2 running through it powered by an Emotiva A100 and it gets mighty loud and sounds great to my ear. Easy to set up and use and no problems to speak of. If you've got a decently powerful speaker amp (or a particularly fancy one) in your existing chain and want to try out electrostatic headphones, this thing is absolutely a great buy.


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