Manley Labs Absolute Headphone Amplifier

 

“I have reviewed countless headphone amplifiers and the Absolute is absolutely the most elegantly designed, intensely musical, and extremely flexible of them all!”

 

With over three years of development in its creation, Manley has drawn from its 30 years of experience in conceptualizing and developing each precise element of this multi-talented unit. This masterpiece embodies high-performance flexibility for every person to be able to custom compose sonic performance reliably, repeatedly, or even spontaneously. Artistic expression with sound!

Oh, and by the way, it is also a Line-Level Preamplifier!

There are fifteen independent controls available, each of which was exhaustively developed for convenient adjustability and aural variety. Two selectable stereo RCA jack pairs receive the input signals. Even these RCA jacks are of our own design. Teflon® insulated and gold plated, we have been producing these excellent RCA jacks since the mid-1990s.

The volume is controlled on the facia by the sexy front thumb wheel and also by the included Radio Frequency remote control, both of which operate a precision stepped relay ladder matrix attenuator in half dB steps.

The RF remote can be operated anywhere in the home, even through walls or cabinetry, especially useful when using the unit as a stand-alone preamplifier. Next to the front volume control wheel you’ll find the Mute switch to instantly kill the signal. Spinning the volume wheel all the way to minimum also mutes the signal. There is also a user adjustable Headphone Overload Protection System which declares maximum output level to protect precious headphones and your ears!

And you know how maddening it is to try to listen to a mono LP record on headphones – which is why we have provided a MONO switch!

In case your source needs some correction or if your own ears do not hear equally, we have included a Balance Control which can swing the signal up to 72dB either way. In its center detent position, this special balance control is completely out of the circuit. Also to be able to execute some sonic authority over what is handed to you in a given recording or to just make your headphones sound nicer (to you!) we have provided historically proven pleasing and gentle Tone Controls – and these Baxandall Bass and Treble equalizers can be completely bypassed at the push of a button. Try them! We think you really will enjoy having the choice to enliven and enrich your sonic experience.

Along those lines, the Variable Feedback control allows you to control the amount of overall negative feedback applied to the amplifier from 0dB, or no Global Negative Feedback, to 10dB of NFB. 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. Feel free to play with this knob and listen for the not-so-subtle diversity that altering the amount of feedback provides. It’s one of our favorite circuit tricks and we’ve been pulling this one for decades!

Ah! And our other coolest tonal trick: Switching Topology!
We’re pretty sure we originated this concept in the audiophile world back with the Manley SE/PP 300B power amplifiers and it’s only because we have our own in-house magnetics department that we are able to devise such complaisant output transformers that can accommodate such radical demands. 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. Interestingly, the output tube stage can be switched on-the-fly between all-triode Push-Pull to Single-Ended topology. This completely alters the harmonic structure from odd-order to even-order and basically halves the output power again providing yet another spicy ingredient to flavor the sound.

Additionally, with a push of a button, these transformers cycle through three ranges of output loads accommodating headphones from 12 to 600 Ohms or greater. Choose between three sets of outputs: the expected 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 this component as your line-level preamplifier in your existing hifi system. The Bypass Thru Mode sends RCA Input 1 directly to the RCA Outputs, when in STANDBY mode. Useful, as your main audio system sources can drive either playback system without having to change upstream cabling.

The Absolute Headphone amplifier incorporates our 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 resulting sound is fast and dynamic with a deep punchy bass, deadly-quiet inky blacks, and superior headroom.

The 6AQ5 or EL90 is the vacuum tube used in the output stage of the Absolute Headphone amplifier. It is well suited for our purposes in a headphone amplifier. The tube is configured as a triode due to the low power requirements needed for headphone use. This tube is widely available from well-known manufacturers such as RCA and GE. The tubes can be ordered as a matched quad and for ease of use the tubes do not require biasing. Simply plug them in and forget ‘em!