Review: HeadAmp AE-2
portable headphone amplifier
retail price at press time: $349
originally published: April 27, 2008
re-edited & updated: November 30, 2008
- download a printable 6-page PDF version of this review
Released back in 2005, the AE-1 was the first portable amp from HeadAmp Audio Electronics, and for about a year was one of the most popular portable amps on the market. It wasn't without its problems though, which included a high noise floor, a discontiguous frequency response, and silk-screening that rubbed off. HeadAmp ceased production on it in 2006 and promised an update on it, finally releasing the update in February 2007 as the all-new AE-2.
Still built in the same solid brushed-aluminum block, the AE-2 looks and operates just like its AE-1 predecessor, but features all-new sound. For this review, I bought and listened to three AE-2 units, but primarily used one unit owned from February 2007 through April 2008.
I usually expect solid-state amps to sound solid-statey - linear, in other words, as far as frequency response goes. "Neutral" and "flat" are standard expectations of mine when it comes to solid-state. A "flat" amp is theoretically a "transparent" amp, an essential wire with gain, that simply passes the sound of the source to the transducers, so when I listen to the ideal solid-state amp, I expect to hear the sound of the source, not the sound of the source plus the amp.
For reference, all previous amps I've heard in quiet conditions are listed in my profile on Head-Fi.
Digital Sources (CDPs w/ Signal Cable Silver Resolution Reference power cord):
- Accuphase DP-500, Arcam FMJ CD33, Plinius CD-101, iAudio X5 (DAP)
- Harmonic Technology Pro-Silway MKIII+ (RCA)
- PS Audio xStream Transcendent (RCA)
- Signal Cable Silver Resolution Analog (RCA)
- VH Audio Spectrum Ag (RCA)
- Signal Cable SilverMini (RCA-mini)
- AKG K340 & K701 re-cabled w/ SAA Equinox
- Audio-Technica ATH-W5000, ATH-AD2000, ATH-ESW9, ATH-ES7, & ATH-CK7
- Denon AH-D2000
- Klipsch IMAGE X10
- Grado RS1
- Sennheiser HD650 re-cabled w/ SAA Equinox
- HeadAmp Gilmore Lite v2 w/ DPS, Pico, & AE-1
- Practical Devices XM5
- Rockhopper Audio Mini³ High-Performance Edition
- RSA Emmeline Hornet M
A Fine Frenzy - One Cell In The Sea
Alison Krauss - Lonely Runs Both Ways, New Favorite, & So Long So Wrong
Julie London - The Very Best of Julie London
Massive Attack - Mezzanine
Orbital - The Middle of Nowhere
Porcupine Tree - In Absentia
Renee Fleming - Thais
Sarah Brightman - The Andrew Lloyd Webber Collection
The Crystal Method - Community Service, Community Service II, & Vegas [Deluxe Edition] (2007)
Thievery Corporation - The Mirror Conspiracy
About the AE-2
The AE-2's specifications as listed on HeadAmp's Web site:
Battery Type: Lithium-Ion
Battery Life: ~30 hours per charge (w/ 3 hours for recharge)
Frequency Response: 5Hz-50KHz +/-0.1dB
Signal-to-Noise Ratio: >100dB
Total Harmonic Distortion: <0.005%
Stereo Crosstalk: >85dB @ 1KHz
Gain (selectable): 2x/6dB, 4x/12dB, 9x/19dB
Input Impedance: 50K ohms
Output Impedance: less than 1 ohm
Output Voltage: 8 Volts peak to peak
Output Power: 500 mW
Inputs/Outputs: 1 RCA input/loop out, 1 3.5mm input/loop out, 1 3.5mm headphone out
Chassis Dimensions: 2.75"x3.5"x1.1"
Weight: 7 oz / 200 g
Amplification on the AE-2 is achieved through the Analog Devices AD8397 op-amp, which HeadAmp selected for its linear, high output current to allow for proper driving of most power-hungry headphones.
The AE-2 is completely encased in a solid brushed aluminum block that's available in black, silver, bronze, blue, or red. Not all of these colors may be currently available as you read this (and there may be others too), so check for the latest info on HeadAmp's Web site. Colors for the chassis body and front/back panels can also be interchanged - for example, a black body with silver front & back panels, or a bronze body with black front & back panels. In addition to these color options for the chassis, there are also color options for the power & charging LEDs (ask HeadAmp for details), as well as the volume pot, which itself can be requested as either polished or brushed. The body chassis may also be available in a mirror-polished finish (like on the Pico, HeadAmp's other portable amp), ask HeadAmp for details on this as well.
Technical differences with the former AE-1 amp include:
- complete internal re-design
- higher output power (along with a correlated drastic reduction in battery life from ~120 to ~30 hours)
- lower noise floor (down to inaudible from audible)
- three-way gain accessed via DIP switches on the bottom
- Li-Ion battery smart charging
- laser-engraved printing to avoid rubbing off
AE-2 vs HeadAmp's Line-Up
HeadAmp's discrete GS-X, GS-1, and Gilmore Lite amps are each based on the well-known Dynalo circuit designed by Dr. Kevin Gilmore, and share a common sound - a trademark HeadAmp/Gilmore sound in fact, that makes them unique. These AC-powered home amps are essential wires with gain and amplify the signal as cleanly and linearly as possible, to sonically "disappear" so you don't hear the amp, but rather the source component. The portable AE-2 seemed to inherit this trademark sound despite its inherently different circuit design and topology, as it too was as transparent as the GS-1 - so strikingly flat and clean that I'd go so far as to call it the best I've heard from a portable amp in that aspect, to date.
I did directly compare the AE-2 to the Gilmore Lite and GS-X as well (not only the GS-1), and found that while it sounded a lot like them, it also clearly wasn't at their level, not even matching the Gilmore Lite, as that amp simply crushed it sonically in multiple aspects. The GL tracked faster, allowing musical elements to emerge from the background more distinctly with more highlighted attacks, with no obvious lack of timing. Its slight treble tendency also helped to make it sound more detailed, which it definitely was - it revealed more background/foreground discrepancies and uncovered & focused in on buried layers more. The GL also produced more accurate, faster-hitting bass with better control, as the AE-2 was a bit loose-sounding in comparison. And in terms of soundstage, the Gilmore Lite simply went deeper to sound more open in the back. In short, the GL, now $399 and $50 more than the AE-2, is a definite step above it sonically, and anyone on the fence between the two who doesn't care about battery power or physical size should get the Gilmore Lite.
AE-2 vs the Competition
Of amps in current production, the AE-2's nearest competitor is the $370 Emmeline Hornet from Ray Samuels Audio, which I was able to compare it to. I also compared it against the High-Performance Edition of the Mini³ built by Rockhopper Audio, a much cheaper portable amp at $125, available as a DIY project detailed on the pages of www.amb.org.
On Massive Attack's "Inertia Creeps" from its Mezzanine disc, the AE-2 timed the best and gave the best sense of detail retrieval, along with the biggest soundstage, with a convincing left/right alignment of the musical layers. The ominous belly drums sounded the most complete on the AE-2, with the initial slam and the fast decay of the membrane. The rhythmic bass pulse also went the deepest in the group on the AE-2, and the mysterious opening clink effects of the track came out the clearest on it - no haze or blur at all, just perfectly in-focus, creepy notes as they precede the oncoming belly drum. Robert del Naja's vocals were also full and filled out, with no added emphasis on the "clearly" and "nearly" lyrics. The RSA Hornet and Rockhopper Mini³, in comparison, went in different directions. The Hornet was more visceral in the bass region, and forcefully harder on the belly drum - almost aggressive, and considerably more ominous-sounding. The Hornet, however, was not as detailed or clear as the AE-2, as it blurred the opening creepy notes along with the subtle buried details. The Mini³, on the other hand, had some bass tilt, enough that it didn't sound very agile and fast. It wasn't very detailed-sounding either.
The AE-2 showed continued prowess on Thievery Corporation's "Samba Tranquille" from The Mirror Conspiracy, particularly on the rhythmic rat-a-tat percussion line. It was extremely agile and articulate, allowing every note to be fully heard without sounding slow or laggy. The rhythmic double bass too was rendered very swiftly. There was also a convincing club-type feel of space, with a fair amount of venue air, especially around the instruments. The AE-2 wasn't perfect though, as the Mini³ revealed an acoustic bass movement on the 4th beat, along with a backwards push on the position of the percussion line. The RSA Hornet showed some disparity on this track - it didn't gel the instrument positions together very well, and it wasn't very quick on the percussion line. In its favor though it made this track sound very self-assured and direct, and forceful as well, that made its version the most faithful samba-danceable.
With Alison Krauss specifically, on such tracks as "Goodbye Is All We Have", "Unionhouse Branch", "The Lucky One", and "So Long So Wrong", the AE-2 consistently conveyed the fragility of her voice and the sense of it cascading on thin air, radiating her voice into space with a crystalline tint so pure, it almost felt like a frequency tone, for those moments when she tilts her voice that way. The amp also consistently swept through these tracks with a class and grace that felt like too much of a good thing with the Arcam FMJ CD33. There was a little too much finesse with the amp & CDP pairing - highly detailed but at the expense of mid-range body. The inner groove of Union Station didn't exactly translate well on the AE-2 - the band felt more detached and separated on it.
Indeed, lack of proper mid-range and some dynamics seemed to be the AE-2's main drawback in repeated listening across Sarah Brightman's The Andrew Lloyd Webber Collection and Renee Fleming's Thais. It didn't swell or punch very well, and didn't convey the drama, vocal power, and dynamic range to either Sarah Brightman or Renee Fleming. While it did convey more treble sparkle on violins and more nuance on lyrics, along with projecting greater spatial expanse, it mostly failed to flare up or intensify sudden bursts in volume or punctuate the dramatic, operatic dialog as it should have been. A Fine Frenzy's Alison Sudol and Julie London were also negatively affected by the amp - Sudol sounded less heartfelt and heavily sad, and London sounded more disembodied and detached on it compared to the other amps.
The AE-2's bass made up for this a bit, as it carried plenty of power, presence, and speed like a huge racquetball. As that might imply, it was plenty fast and agile, but definitely large-sounding with a high impression of mass being thrown around. This was a good thing of course, as the synthesized bass of most tracks by The Crystal Method should sound massive, and it was an appreciated additive quality. Ceasefire's "Trickshot" on TCM's Community Service mix CD was especially satisfying on the Audio-Technica AD2000, as the AE-2 provided plenty of low rumble, particularly on the ultra-low bass push that doesn't start until 1:01. There was more "gut" on this track than with any other amp that was compared.
The AE-2's soundstage proved to be another drawback though, as it did not properly delineate instrument distances relative to each other on the z-axis. Oh it did create wide, open soundstages with plenty of free-roaming air and space in and around instruments, but it had a tendency to make every instrument sound like they were all on the same depth plane. Near and further away instrument positions, for example, did not sound quite as distant as they should have sounded.
Over the time that I owned the AE-2, I was able to use it with a wide array of headphones/IEMs: AKG K340 (400 Ohms), AKG K601 (120 Ohms), AKG K701 (62 Ohms), Audio-Technica ATH-CK7 (16 Ohms), Audio-Technica ATH-ES7 (30 Ohms), Audio-Technica ATH-AD2000 (40 Ohms), Audio-Technica ATH-W5000 (40 Ohms), Beyerdynamic DT250-80 (80 Ohms), Grado SR225 (32 Ohms), Grado RS-1 (32 Ohms), Klipsch IMAGE X10 (50 Ohms), and Sennheiser HD650 (300 Ohms). The AE-2 drove all of these headphones with relative ease, but of course the one it struggled with the most was the AKG K340, a very demanding headphone that runs best from high-power tube amps or integrated amps. The AE-2 just barely drove that headphone properly - it provided enough moderate volume but it simply could not drive the K340 past the 2 o'clock position before distorting. So caveat emptor with 300-600 Ohm headphones.
The AE-2 was more than up to the task with all the other headphones though, as it drove them very well and sounded decent with everything too, pairing the best with the SR225, K601, ES7, AD2000, DT250-80, and HD650, by adding some helpful clarity and soundstage and tightening the bass. There were absolutely no noise issues with either the Audio-Technica CK7 or Klipsch IMAGE X10 IEMs either, as the amp maintained a silent background at all volume levels. Low gain was very useful with these headphones, as the AE-2 provided the right amount of volume fine-tuning to achieve any desired volume. It did sound better with the Klipsch X10, as their IEM is more of a mid-range & bass-centered one, and the amp cleaned it up better.
Though it has a relatively non-dynamic mid-range, along with a single-planar-depth soundstage, HeadAmp's AE-2 is still a landmark achievement in sound for portable headphone amps. It offers reference-grade sound well above its colored-sounding competition and it can easily drive most dynamic headphones without issue to boot. Highly recommended for adding a shot of hi-fi audio to any portable audio system, or even a small home system.
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Edited by Asr - 4/30/16 at 6:37pm