Gramophone Dreams #35: ZMF & Hagerman headphones & headphone amplifiers Page 2

The ZMF Vérité Closed were dancing in the same ballroom as the top models of Focal's headphone lineup. The Vérités' basic sound reminded me a lot of my beloved Focal Clear—and even more of the Focal Stellia headphones I've auditioned at CanJams. But to my taste, the ZMF Vérité Closed headphones were more naturally focused and inherently musical than any of Focal's premier offerings.

Oh, no: I'm having a memory!
The most conspicuously lifelike, real-sounding headphones I've been privileged to audition were a pair of Sony MDR-R10s manufactured in 1989. I heard them only a few years ago, but when I did, I knew instantly: Their realism had no equal, anytime, anyplace. If recollection serves me, the R10s had closed wood cups, lambskin earpads, and biocellulose dome diaphragms. They even looked like the Vérités. But wait a minute: As I swear on the memory of my mother's voice, ZMF's new closed-back Vérités come closer to those MDR-R10s in basic sonic character than any other headphones I've auditioned. In fact, they may even exceed Sony's cult classics in their illusion of speed and transparency.

ZMF Pendant Headphone Amplifier
High-impedance headphones, like the Auteurs and Vérités, present amplifiers with a mainly resistive load, and because of that they can sound unbelievably clean, dynamic, and low-distortion with old-school single-ended tube amplifiers like ZMF's Pendant. Designed by Justin Weber of Ampandsound, the ZMF Pendant costs $1999.99, with upcharges for a custom wood chassis ($300) or a vintage tube set ($200). My review sample was equipped with the stock JJ-branded tubes, which are good-sounding but could likely be improved on by being replaced with vintage new old stock tubes. The Pendant's 12AX7/6BQ5/6CA4 tube set seems perfectly suited for this type of experimentation.


The Pendant uses a single EL84/6BQ5 pentode (per channel), connected in Ultralinear mode. It is rated at 2.5W into 8 ohms and 1.5W into 300 ohms, which, with 99dB/mW headphones, is the equivalent of putting at least 1000 watts into most box speakers.

I believe that careful "gain management" is essential to achieving optimum sound with any perfectionist headphone. To that end, the Pendant allows users to select a 12AX7 (high gain: µ = 100), 12AT7 (medium gain: µ = 60), or 12AU7 (low gain: µ = 20) as the amplifier's driver tube. When driving ZMF, Audeze, and Grado headphones, I used a 12AU7; with the HiFiMan HE6se, I used a 12AX7.

This tube-swap gain-adjust feature adds another, almost infinite, dimension to the sonic possibilities of tube rolling.

On a more practical level, the Pendant provides two switchable RCA line-level inputs and two ¼" headphone jack outputs on the front—one for typical low-Z phones and one for high-Z phones—plus an Alps volume control.

Pendant sound: I first listened to the Pendant with the 12AX7 driver, but with the Vérités, the gain was too high. With the high-Z input, instead of blackness, a modicum of low-level gurglelike noise was audible when the music wasn't playing. When I swapped in a lower-µ 12AU7, the amp relaxed considerably and became dead quiet, as well as sweeter and more flexible, rhythmwise.

The soundtrack to the 1995 film Dead Man is essentially an artistic collaboration between Jim Jarmusch, the film's director; John Hanlon, the soundtrack's producer and engineer; and Neil Young, who composed and performed the score (16/44 FLAC Vapor Records/Tidal and Qobuz). The opening track, called "Guitar Solo No.1," is a sound collage and one of my favorite deep-listening tracks. It is also a sonic marvel that the $2599 Feliks Audio Euforia OTL amplifier driving the ZMF Vérité headphones made into a dense, dark sea, teeming and pulsing with primordial life. The Feliks amp took me inside the recording, where the microdetail looked sharply focused but simultaneously diffused and shadowy, like a coral reef at night. The Vérités + Feliks amp made sensuous, vivid sound that leaned slightly toward dark and misty.

With the ZMF Pendant, that same coral-like microdetail became tangibly solid and more precisely focused. Inner detail was more evenly illuminated. The Pendant made spoken words more intelligible and images more distinctly drawn.

The Pendant seemed like the best all-purpose headphone amplifier I have used since I died and flew to heaven reviewing the $5899 Woo Audio WA5.

Hagerman Audio Labs Tuba
Known best for his moderately priced Bugle and Cornet phono stages, and most notably for his $7200 Trumpet Reference phono stage (reviewed by MF in Vol.37 No.2), engineer Jim Hagerman recently expanded his diverse product range with a $649 headphone amp called the Tuba, which, like the Pendant, uses an EL84 output tube (footnote 1).


In one of the great moments in audio journalism, Michael Fremer posted a video on Analog Planet's YouTube channel that played the same record with the same expensive phono cartridge on two wildly different turntables: the $4k Technics SL-1200G and Mikey's reference Continuum Caliburn, which, with the SAT tonearm, "costs as much as a house." (footnote 2)

In the video, while the music played, Mikey's camera stayed focused, first on the Technics and then the Caliburn, but the viewer did not know which turntable was actually making the sound. The viewer was supposed to guess whether the sound matched the turntable image or was reversed. I had just finished reviewing the SL-1200G, so I recognized its bright, clean, well-described detail, precision sorting, and short, attenuated note decays. The Continuum, on the other hand, displayed a "long," darkish, extremely atmospheric sound that was softer than the Technics.

Not surprisingly, the majority of listeners (none of whom had ever experienced this new Technics) thought the $4k turntable was the expensive one because it seemed clearer and more precise. They could not imagine dark and atmospheric as accurate.


I tell this story now because I think the Hagerman Audio Labs Tuba headphone amp, driving ZMF Vérité headphones, sounds exactly like the Technics turntable in that comparison. Compared to the ZMF Pendant or the Feliks Euforia, which sound like the Continuum, the Tuba has a clear but "short" sound—especially for a tube amp. (Interestingly, the Technics turntable and the Tuba amplifier both employ switch-mode power supplies.)

Both the Pendant and the Tuba are transformer-coupled to two ¼" output jacks: one suited for high-impedance headphones such as the 300 ohm ZMFs, and the other for low-impedance headphones such as the 32 ohm Grado GS3000e. (On the Pendant, these are labeled High Z and Low Z; on the Tuba, they're labeled Hi and Lo.) But that's where the similarities end. The Tuba and the Pendant look radically different and represent completely different approaches to headphone amplifier design.

Having built scores of DIY tube amplifiers, I admit to being partial to Jim Hagerman's modestly sized (6" × 10" × 3.5") aluminum utility-box chassis with its gray-green powder-coat finish. The Tuba is rated at 350mW into 32 ohms, which is enough power to drive most common headphones, but still a lot less than the 3W into 32 ohms developed by the Pendant, which uses the same output tube. The main reason for this disparity is that Hagerman's Tuba is triode-wired while, as noted above, the Pendant's EL84 is connected in Ultralinear mode.


As I studied the Tuba schematic in the owner's manual, I realized that the output circuit is configured as a constant-current/parallel feed design, with the tube's control grid driven not by a tube or solid-state voltage amplifier, but directly (through a 50k ohm log potentiometer) by the output of whatever DAC or phonostage it might be connected to. This limits maximum voltage gain to about 6dB.

The Tuba does not use global feedback or degenerate the tube's output. In contrast, the Pendant's Ultralinear output stage requires at least a few dB of global feedback to stabilize its more traditional all-tube circuit.

I call the Pendant's circuit "more traditional" because its EL84 is driven by a conventional voltage amplifier stage and uses a high-voltage power supply that is tube-rectified and choke-filtered. That's in stark contrast to the Tuba, which uses a switch-mode supply powered by a 15V wall wart. Obviously, Hagerman was aiming for lightweight, low cost, low gain, and quiet.

For my first test of any headphone amp, I always use the lucid HiFiMan HE6se headphones ($1800). Their 50 ohm impedance and 83.5dB/mW sensitivity show me instantly whether an amp has sufficient gain and power to be considered "all-purpose." The HE6se requires at least 3W (and a lot of gain) to dance and become its fully wondrous self. I doubted the Tuba could handle it, but I was prepared to be surprised.

Driven from the Tuba's Lo output, the HE6se made the relatively undemanding (powerwise) Dakh Daughters album sound dull, slow, blurred, and rolled off at the top and bottom. Obviously, not a good match.

For a fair comparison, I auditioned the HE6se with the $399 Schiit Jotunheim, a fully balanced headphone amp/preamp that's rated at 3W into 50 ohms and 900mW into 300 ohms. The Schiit amp driving the HiFiMan HE6se headphones played "Yaponske Kino" with a dynamic but noticeably "transistor" sound. Its presentation of the Dakh Daughters included tight, tuneful bass, a lustrously detailed midrange, and attractively lit high frequencies.

Obviously, the Tuba preferred sensitive headphones like the ZMF Vérités, which showcased all the Tuba's strengths. I assumed therefore that it would also like the equally sensitive (99.8dB/mW) but lower impedance (32 ohms) Grado GS3000e open-backs. Which it did. The Tuba-Grado combination generated a tidy, naturally detailed, highly musical sound that I found 100% enjoyable. Midrange tone was exemplary.

Hagerman specs the output impedance at 5 ohms for the Lo output and 35 ohms for the Hi output. That makes the Lo output fine for 50 ohm headphones, but maybe a little high for Audeze's 20 ohm (95dB/mW) LCD-Xes. This combination did sound underdamped, but it delivered the "longest" and most tubelike sound I achieved with the Tuba.

So then...
I am guilty of being slow on the uptake when it came to grasping the full measure of Zach Mehrbach's ZMF creations. The Auteurs' unique ability to disappear camouflaged their pure, understated, liquid magic. The Vérités, however, were not so subtle: Their speed, dynamics, and radical transparency put them instantly among the elite headphones of all time. I was completely seduced.

My months-long investigations into the ZMF aesthetic were made delightfully easy by my simultaneous discovery of ZMF's Pendant headphone amp, which I would now rank as the third-best headphone amp I've used, after the Woo Audio WA5 and the HiFiMan EF1000.

I was hoping the Hagerman Labs Tuba amplifier would be a budget discovery—and indeed it played most headphones really well. But its limited gain and low power prevented it from being considered as an all-purpose giant killer.

Next month's Dreams will feature genuine high voltages: I will introduce you to Linear Tube Audio's new Z10e, a 12W, EL84 tube loudspeaker amplifier, preamp, and electrostatic headphone amplifier, which I'll audition with Stax SR-009S, HiFiMan Jade II, and Dan Clark Audio's Voce electrostatic headphones.

Footnote 1: ZMF headphones, 3841 Ridgeland Ave., Berwyn, IL 60402. Web:

Footnote 2: Hagerman Audio Labs, PO Box 61911, Honolulu, HI 96839. Web:

Footnote 3: The Tuba's Mullard-branded tubes are made in Russia, while the Pendant's JJ-branded tubes are made in Slovakia.

Footnote 4: See and

Bogolu Haranath's picture

The Manley Absolute tube headphone amp ($4,500, reviewed by Inner/Fidelity and Hi-Fi News) should work well with high impedance headphones like ZMF, top models from Sennheiser and Focal etc. ........... That Manley has various options including multiple adjustable negative feed-back options :-) ..........

Bogolu Haranath's picture

After reviewing the Manley headphone amp, Ken Kessler (HFN) said 'Absolute?, absolutely' :-) .........

JRT's picture

Monoprice Monolith THX AAA 887 (product 39359) is $399.99, plays cleanly with load invariant flat response (for most usual headphone load impedances).

Bogolu Haranath's picture

Manley has tubes ...... Lots of glorious tubes ..... and, gorgeous, fantastic and stunning looks :-) .......

ASR reviewed that Monoprice headphone amp ......amirm should try the Manley with his HD-650 ....... He may not go back to the Monoprice :-) .......

JRT's picture

On badly flawed recordings, it might be useful to change the sound. On well recorded material, I would prefer to avoid adding crap that doesn't belong in the mix.

If you want to spend thousands on a device that changes the sound by including euphonic distortion, then get something well designed for that purpose such as the mastering version of the Manley Massive Passive. It can be run without filters to add the sound of the tube amplifier section (as Bob Ludwig has advocated) to mask "digititis" (poorly engineered digital processing in the recorded material), or parametric equalization filters can be also be applied if useful. The adjustable parametric EQ might be more especially useful with headphones. Note that the Massive Passive is not truly parametric as adjustments do interact.

The signal is pro-level differential on balanced impedance interconnection, so should be utilized in a setup that likewise utilizes that.

Bogolu Haranath's picture

We discussed this before ........ That Massive Passive can give regular consumers massive nervous break-down ....... We can use less expensive and less complicated external parametric or graphic EQ, which can give us very satisfying results :-) ........

Bogolu Haranath's picture

Well established companies like Sonarworks provide EQ software for headphones ...... Dirac has recently announced that they are gonna offer EQ software for headphones :-) ........

Bogolu Haranath's picture

The $2,500, ZMF Verite deserves nothing less than the Manley Absolute :-) ........

Bogolu Haranath's picture

That 'Yaponske Kino' sounds kinda like 'bad guy' by Billie Eilish :-) .......

Bogolu Haranath's picture

HR could compare the ZMF Verite with the Sennheiser HD-820 closed back headphones ($2,400) :-) .......

Bogolu Haranath's picture

It would be interesting to compare the analog disc of that Canteloube album by Natania Davrath with CD-res and/or Hi-Res digital recording :-) .........