Manley Laboratories Absolute Headphone Amplifier

To fully understand why the MANLEY Absolute Headphone Amplifier is such a great deal, you must first understand MANLEY’s pedigree. Back in the late nineteen eighties, MANLEY began life as the Lexus to VTL’s (Vacuum Tube Logic) Toyota. That is to say that MANLEY began as David Manley’s rare air signature line of VTL products, producing initially one of the most coveted tube pre-amps ever made. In 1993, after David and EveAnna Manley spun off the MANLEY brand as its own company with separate manufacturing apart from VTL, MANLEY's pro studio products became the predominant revenue generators, but all this time, Manley Labs has remained true to its audiophile roots continuing to create some of the finest tube amps available.

Having reviewed the MANLEY Absolute Headphone Amplifier three years ago (https://headphone.guru/manley-absolute-headphone-amplifier-the-makings-of-a-legend/) it was with great excitement and anticipation that I greeted acquiring one of my favorite tube amplifiers to use as my reference tube amplifier, and hence am writing this follow up review.

The MANLEY Absolute Headphone Amplifier:​

The MANLEY Absolute Headphone Amplifier boasts of fifteen independent operational controls “each of which was exhaustively developed for convenient adjustability and aural variety.” Two selectable stereo RCA jack pairs of their own design, Teflon® insulated and gold plated, receive the input signals. The volume is controlled on the facia by a front thumbwheel or by the included RF remote control employing a precision stepped relay ladder matrix attenuator in half dB steps, with the Mute switch situated next to the volume control wheel. Vertically mounted just in front of the tubes you will find Baxandall Bass and Treble equalizers that can be completely bypassed via a separate button, and a Balance Control which has a signal swing of up to 144 dB (In the center detent position the balance control is completely removed from the circuit).

In addition to the EQ bypass switch, there is a button for mono, source, output (¼” TRS Headphone Jack, a 4-pin XLR Balanced Stereo Output for your high-end balanced headphones, and a set of stereo RCA outputs to use the Absolute Headphone Amplifier as a line-level preamplifier in an existing HiFi system) and a button that cycles the transformers through three ranges of output loads (Low 12-50 Ohm, Mid 50-200 Ohm, High 200-600 Ohms).

There is also a selectable Bypass Thru Mode that sends RCA Input 1 directly to the RCA Outputs, when in STANDBY mode, as well as a user-adjustable Headphone Overload Protection System which allows you to preset a maximum output level.

Which brings me to the two most interesting and unique features; the first being the ability to switch on-the-fly between all-triode Push-Pull to Single-Ended topology. Essentially, in Push-Pull mode the Harmonic Distortion is significantly lower, power output is greater and noise floor should be lower, whereas Single-Ended completely alters the harmonic structure from odd-order to even-order which is more musical.

The other is my favorite feature the Variable Feedback control which allows you to control the amount of overall negative feedback applied to the amplifier from 0dB, or no Global Negative Feedback, to 10dB of Negative Feedback.

“Negative Feedback in electronics is when a small portion of the output signal is re-introduced back to the input signal to provide a more stable and beneficial corrective result. This control is very useful when determining how “tight” you want your amplifier to sound. For example, a simple female vocal with minimal percussion can sound more intimate with very little feedback, but a complicated symphony orchestra passage may sound better positioned with more feedback. Applying different amounts of negative feedback can also affect the slew rate and apparent “speed” of the sonic character. Other aspects for which to listen include placement, forward or relaxed, darker vs shimmering, or punchy vs mellow.”

On to technical features; the Absolute Headphone Amplifier features custom hand-wound air-gapped dual-mode MANLEY IRON® output transformers, designed and manufactured at the Manley Labs factory in California. It also incorporates their own innovative purpose-designed-for-audio High Voltage switched-mode power supply. “All super-low impedance DC rails are fully regulated and worlds quieter than any linear supply we have ever encountered.”

The solid billet chassis for the Manley Absolute Headphone Amplifier in three color options: Black, Copper, and Silver, and feature hand-rubbed walnut-burl veneer accents for the headphone headband and earpad rest areas.

The unit I received was Copper fitted with Ruby 12AX7WBC HG+ input tubes and RCA 6AQ5A vacuum tubes in the output.

The Soundcheck:​

This time around I have two world-class DACs to use as source. One is a triode tube based Sigma/Delta DAC, the iFi Pro iDSD 4.4, and the other is a Current Mode Ladder DAC, the Audio-gd R2R-1 FPGA PCM/DSD DAC, and a slew of reference headphones. Both DACs and the Amplifier were connected using 2-meter Cardas Iridium Power Cables, a 1-meter pair Cardas Iridium Single-Ended (RCA) Interconnects, and a 2-meter Cardas Clear Serial Bus Rev 1USB Cable.

Starting with my Dan Clark Audio ETHER2 Orthodynamic Headphones and the iFi Pro iDSD 4.4, with the MANLEY in Single-ended mode and the feedback set to max, I queued up Qobuz to see what was on the docket. Selecting Para One's “SPECTRE: Machines of Loving Grace” (24-bit/44.1kHz) I was treated to palpable bass and incredible musicality in a spectacularly huge and spacious soundstage. While it is hard to judge timbre and tonal balance with EDM (Electronic Dance Music) the presentation was clear and linear. While the music was billed as EDM it falls out heavily on the electronica side in the vein of Mike Oldfield or Tangerine Dream offering what at least sounded like real percussion instruments for the song “Virtual Satori”. The resolution was excellent presenting defined images of the plethora of woven sounds. It is worth noting that, the ETHER2s being my most efficient headphones short of IEMs, the noise floor was lower than that of my DAC, enhancing both micro detail and dynamic range, an extreme accomplishment for a tube amp.

Switching to my Dan Clark Audio ETHER C Flows, which are a little more neutral than the ETHER2s, I put on my primary acoustical test track, Stravinsky’s “The Firebird Suite” as performed by Eiji Oue conducting the Minnesota Orchestra (“Stravinsky” – DSD), and once again set in a vast soundstage the timbre and tonality of the instruments was dead on, each set in its own space, easily delineating similar sounding instruments as they wound their individual melodies into the tapestry of sound. The extreme dynamics of the crescendos were fully realized And as before, musicality was the watchword of the day.

Now was time for the real torture test the HiFiMan HE6se Planar Magnetic Headphones known as one of the hardest to drive headphones out there, and at this time I decided to also step over to the Audio-gd DAC. Selecting my subsonic test track “Can-utility And The Coastliners” (Genesis – “Foxtrot” – DSD) I ran it through a couple of times in Single-ended mode. Though I had to run at full volume the performance was fantastic, digging deep into the subsonic offering up natural and realistic tonality with lifelike musicality. Once again the detail and dynamics were excellent, and the soundstage was spacious and three-dimensional. Switching to Push-Pull I was able to eke out a few dB of volume at the cost of slightly harder sound. If I wanted to achieve painful levels of volume I could also turn down the negative feedback and gain about 6dB of volume but this brought the musicality down to the level of the better tube amps in its price range. Now I will admit that the effect is subtle and many listeners will be perfectly happy with the sound with 0 feedback in Push-Pull mode (some will actually prefer that sound) I will probably always opt for that little bit more liquidity in the midrange.

As a final test, I hooked up my reference dynamic headphone the Spirit Torino Twin Pulse Isobaric Open Circumaural Headphone. (If I have a complaint about the Absolute Headphone Amplifier it is that the inputs and outputs are all on the back, meaning that even though the footprint is fairly small on my crowded desk, I have to get up and go around the back to change headphones.) Since I had yet to explore Jazz and since the true calling of tube amps is vocal, I chose “The Look of Love” as performed by the angelic Dusty Springfield backed by the incomparable Herb Alpert & the Tijuana Brass (Burt Bacharach – “Casino Royale” – 24-bit/192kHz). It was stage edge in a huge nightclub. Dusty’s voice was honeyed sweet and intimate, the piano was rich and delicate with a Steinway feel (piano is my instrument), and the upright bass offered complex resonant overtones adding a whole level of realism. The horns were textured and dynamic without being abrasive and the percussion was tight, crisp, and impactful.

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Conclusions:​

I’ve said this before but it bears repeating, most people don’t understand why tube amps sound better, or more to the point, why tube lovers prefer tube amps. Electrical Engineers (who are not audiophiles) will say it is because tube amps roll off the highs making them sound warmer and are anemic on the bass emphasizing the midrange basing their assumptions on poorly designed tube amps, and many will proceed to build truly awful sounding “tuby” solid-state amps using this formula. Others will go so far as to say that what people like is the high levels of THD produced by tube amps ignoring the fact that these levels are still well below the threshold of hearing. The reality is that solid-state amplifiers produce a distortion that tubes cannot call Transient Intermodulation Distortion, which is caused by the negative feedback loop (which is why many manufacturers eschew negative feedback at the expense of audible levels of THD or insanely expensive parts, also why it is silly for a tube amp to not have negative feedback) and creates that metallic sound associated with solid-state amplifiers which masks a lot of the micro-detail that makes up the soundstage.

In other words, a properly designed tube amp should have the same bandwidth and linearity as the best solid-state amplifier and just be a little more musical. A few personal audio manufacturers get this, ampsandsound comes to mind, but MANLEY, originating from the peak of audiophile quality high-end audio, has never forgotten this and the MANLEY Absolute Headphone Amplifier embodies this philosophy producing one of the most musical amplifiers I have heard with extreme linearity of tonal balance, epic soundstage, fantastic resolution, a ridiculously low noise floor, and a smooth liquid midrange. I highly recommend that any audiophile should take the opportunity to audition an Absolute Headphone Amplifier if just to hear for oneself the difference between Single-ended and Push-Pull, and the effects of negative feedback. The addition of nonobtrusive EQ controls makes the amplifier appropriate for any style of music and while 1Watt of output doesn’t make it the most powerful option out there, it will certainly be sufficient to drive most of the headphones available. If you are looking for a reference headphone amplifier I can simply think of no better choice.

Manufacturer's Website: MANLEY.com/hifi/mabhpa

Price: $4,500 USD

SPECIFICATIONS:

Amplifier Topology:
Triode Vacuum Tube Output Stage, Switchable Topology Single-Ended or Push-Pull

Vacuum Tubes:
2 x 12AX7 (ECC83), 4 x 6AQ5A (EL90)

Inputs:
2 x RCA (Input 1 & Preamp Output = Pass-Thru when amplifier is in Standby or Off)

Input Impedance:
50 kOhms (Pass-Thru= 300 kOhms)

Maximum Input Level:
7.7 VAC RMS (+20 dBu)
(Conditions: XLR output, PP mode, 16 ohm load, VOLUME max, EQ out, 1kHz sine wave)

Gain:
Load 16 ohm: 12 dB (Min FB), 3 dB (Max FB)
Load 62 ohm: 17 dB (Min FB), 8 dB (Max FB)
Load 200 ohm: 22 dB (Min FB), 13 dB (Max FB)
(Conditions: XLR output, PP mode, VOLUME Max, EQ out, 1kHz sine wave)

Input Sensitivity:
600 mV AC RMS for an output of 100 mW
1.9 VAC RMS for an output of 1W
(Conditions: XLR output, PP mode, FB 12:00 o’clock, 16 ohm load, 1kHz sine wave, VOLUME max, EQ out)

Volume Control:
- Precision Stepped Relay Attenuator 0.5dB per step
- 63dB total attenuation – Volume setting to minimum = MUTE

Outputs (transformer coupled):
1 pair RCA- Unbalanced (Preamp Output)
1 x TRS ¼” JACK – Unbalanced
1 x 4 PIN XLR- Balanced

XLR-pin outs - (Left Channel Pin 1= Signal (+), Pin 2= Signal (-), Right Channel Pin 3= Signal (+), Pin 4= Signal (-))

Output Impedance:
Switchable: Low 12-50 Ohm, Mid 50-200 Ohm, High 200-600 Ohms

Maximum Output Power = 1W into 12 Ohms BW 22Hz-22kHz



Variable Feedback Control (FB):
MIN 0dB
MAX 10dB
(Conditions: BAL output, PP mode, 16 ohm load, VOLUME max, EQ out)

Signal to Noise Ratio:
83 dB (1kHz sine wave, 100mW output, BW 22Hz-22kHz)
(Conditions: BAL output, PP mode, FB 12:00 o’clock, 16 ohm load, VOLUME max, EQ out)

Noise Floor:
-80 dBu BW 22Hz-22kHz
-85 dBu A-Weighted
(Conditions: BAL output, PP mode, FB 12:00 o’clock, 16 ohm load, VOLUME MAX, EQ out)

Channel Crosstalk:
-71 dB (1kHz sine wave, 100mW output, BW 22Hz-22kHz) Left Channel
-72 dB (1kHz sine wave, 100mW output, BW 22Hz-22kHz) Right Channel
(Conditions: BAL output, PP mode, FB 12:00 o’clock, 16 ohm load, EQ out)

Balance Control Channel attenuation:
Left Channel= 72dB (1kHz sine wave, 100mW output, BW 22Hz-22kHz)
Right Channel= 72dB (1kHz tone, 100mW output, BW 22Hz-22kHz)
(Conditions: BAL output, PP mode, FB Min, 16 ohm load, EQ out)

Frequency Response:
Push-Pull= Flat 10Hz – 20 kHz (-1dB @ 40 kHz)
Single-Ended= 20Hz – 20 kHz (-0.5dB @ 10Hz, -1dB @ 50 kHz)
(Conditions: BAL output, 100mW output, FB @ 12:00 o’clock, 16 ohm load, EQ out)

Distortion:
Push-Pull= 0.16% THD+N (BW 20Hz-22kHz)
Single-Ended= 1.0% THD+N (BW 20Hz-22kHz)
(Conditions: BAL output, PP mode, 1 kHz sine, 100mW output, FB @ 12:00 o’clock, 16 ohm load, EQ out)

Supplied with Remora RF remote control

Soft Start, 30 second mute-controlled power-up sequence

Operating Mains Voltage: 90-250 VAC, 50-60Hz, universal works worldwide

Unit Dimensions: 11.5 x 5.5 x 8.2” (LxWxH)

Unit Weight: 12 lbs

Shipping Weight = 13.5 lbs

Packing Carton Dimensions: 17 x 11 x 15”

Power consumption STANDBY mode = 0.5W, Max Power = 80W

Heat Rise above ambient temperature at rear panel: 25ºC or 44ºF

Heat Rise above ambient temperature at side panels: 15ºC or 26ºF