March 09, 2021 11 min read
Review written by Ian Dunmore (@Torq)
When you think ZMF, you tend to think “headphones” - whether that’s Zach Mehrbach’s all-proprietary line of artisanal-quality, wooden-cupped, dynamic-driver masterpieces, like the recent Vérité or Auteur - or their original planar models based on a modified Fostex T50RP platform. But that’s not all that is on offer from ZMF - as in addition to their headphones, upgrade cables and a wide variety of pads (compatible with other headphone brands too), they also have their own dedicated headphone amplifier - the “Pendant”.
The Pendant is a pure-tube implementation featuring a high-power, transformer-coupled design capable of driving almost any headphone that you care to throw at it. It has been developed in collaboration with ampsandsound, a well-regarded designer and manufacturer of tube-based headphone and speaker amplifiers.
The unit used for review here was on kind loan from ZMF and has subsequently been sent to the next eager reviewer for their listening and auditioning.
Features & Options
The Pendant has two headphone outputs, each of different output impedance (OI) referred to as “Low Z” (8 ohms, with up to 3W of power available) and “High Z” (300 ohms, with 2.5W of power on tap), respectively. This aids with matching the output and damping capability of the amplifier with your headphones. As a general rule, you’ll want lower impedance dynamic headphones (150 ohms and below) connected to the Low Z output to minimize frequency response shift, though this is not a requirement.
Options come in the form of a “Vintage/NOS” upgraded tube set ($200) - the specific tubes for which may vary, as well as the option for a custom-wood chassis ($300). The standard chassis for the pendant is black, matching the unit’s top-plate, and as shown below - and it’s quite a fetching finish. For me, given the excellent woods and finishes that ZMF is so well known for in its headphones, I would personally opt for one of the custom woods.
The Pendant is equipped with a pre-out connection, so can be employed either with external power-amplification, or active speakers, for integration into a 2-channel non-headphone setup.
Finally, there are dual, switchable, high-quality RCA-inputs (since this is a fully single-ended design), allowing the connection of two sources and easy selection between them.
The Pendant is a very solid feeling, desktop-sized, unit, without being excessively heavy. The finish is, as with every ZMF product I’ve had my hands on, extremely appealing and of very high quality. There were no creaks, groans or rattles, nothing was loose, sockets were firm, switches positive and the volume pot is buttery smooth.
Inserting and removing tubes, which many tube-amp owners do a fair amount of, especially early on when rolling tubes to find which types/versions they like best, did not result in any perceptible movement in the tube sockets. And the fit was firm and consistent, without being so tight that it would cause concerns for damaging tubes when removing them.
The unit follows the familiar “ampsandsound” plate-on-chassis construction (an approach also used by other tube-focused companies such as Bottlehead and Decware, among others), with transformers, connections/sockets, controls and, most importantly, the tubes all mounted on the top of the main plate, with point-to-point construction for the internal components hidden underneath). This yields a very appealing aesthetic - most tube-amp fans like to see the glow as much as possible - and they are prominently on display here, while also facilitating super-easy access to the tubes.
Due to the top-mounted IEC power-inlet, you may want to consider a power-cord with a 90-degree angled head, but this is a matter of appearance rather than function. The unit was perfectly stable, with no movement at all, even with my heavy, big-gauge, solid-billet power cables in use (not used for listening as part of the review itself).
It is worth noting that the top plate on this unit differs in its tube labels from more recent models, which show the more commonly used references for the tubes used.
Tube amplifiers, especially pure-tube designs, are often assumed to be “warm”, “gooey”, “laid back” and/or “highly colored” sounding by those that don’t have experience with them; though there are certainly some models which would meet one or all of those descriptions.
The ZMF Pendant is not one of them.
Instead, equipped with the stock tube complement, it is punchy, dynamic and quick, with excellent resolution, while maintaining many other desirable traits of tube amplification - such as holographic presentation, expansive staging, solid tonal weight, lucid mids and silky-smooth highs, without the “drag” of an exaggerated, overly warm or tubby, bottom-end nor imposing a “laid back” sense to the delivery.
At the same time, the Pendant responds well to tube-rolling - which lets you tailor the sound in a variety of ways, depending on your personal preferences … something I’ll come back to in the “Tubes & Tube Rolling” section. But for now, I will stick with the stock tube complement - as that is how the main section of this review was conducted.
In More Detail …
Tone is effectively neutral with the included JJ Electronics tubes, though you can push it towards either warmer or brighter signatures with different input and power tubes. There’s no apparent emphasis here, from either output, with appropriately matched headphones. Instruments present naturally, from their lowest registers to their highest, even with the significant range of instruments like the Piano.
Timbre is accurately reflective of the natural sound of the instruments in question, with excellent, even visceral, texture, appropriate body/weight, and preserves the natural damping or reverberation of the piece in question. Instruments that bite, will do so convincingly here, be that the discordant overtones of brass being thrashed, or the initial pluck of a harp or guitar string. While more even/less-stressed, play, on less aggressive instruments, remains pure and smooth.
It’s even possible to discern variations in the timbre as it changes, subtly, with grip and position during longer pieces that have the performer repeatedly mount and unmount their instrument between passages. This is typically the preserve of more exotic amplifier designs - often those relying on much more expensive tubes, so it is particularly impressive to hear this on the Pendant.
Bass delivery is taught, fast and punchy with excellent articulation and sit-up-and-take-notice slam-capability. This is in stark contrast to many tube amplifiers that achieve their “bass presence” by being wooly, loose or bloated. You do need to pay attention to the impedance of your headphones to get the best of the Pendant here - once you start to stray shy of about 80 ohms on your headphones (on the Lo-Z output), bass-quantity will increase at the cost of some control.
The mid-range is pure magic, with proper tonal weight, oodles of detail, so-good-you-can-feel-it rendition of texture, and entirely lucid … even liquid … rendering. With the stock tubes it does not stray into editorialization with that I would call “lush” mids - though you can certainly take it there with alternate tubes if that’s your bag. I have a soft-spot for “lush” mids … which is why I tend to gravitate towards 300B-based tube amplifiers, but that “lushness”, while seductive, is not especially accurate - and accuracy is the side of the fence the Pendant walks with its normal tube complement.
Treble is silky-smooth, completely natural and detail-rich, with absolutely no sibilance, harshness or unwanted tension to it whatsoever. Blaring trumpets and horns bite and glare appropriately, without exaggeration. Cymbals crash and ring, without exaggerated splashiness, and sound like the brass they are with no hints of steeliness.
Dynamic delivery is extremely powerful, with an effortless sense to even the most significant shifts from pianississimo to fortississimo, the abrupt sonic impact of cannon-fire, or Germanic-operatic crescendo. Staccato shifts to and from silence to max-level replay, leave the Pendant completely unfazed. Impact is high. This is a shock-and-awe experience even compared to some of the most dynamic tube-hybrid designs and rivaling more expensive solid-state performers. Ample power-reserves allow unrelenting power and slam, even with demanding cans, and at no point in my listening was there even a suggestion that the Pendant was not “keeping up”. Even with low-impedance planar-cans, a common weakness for (relatively) high-OI amplifiers, the sense of effortless and limitless power reserves was preserved.
This macro-dynamic prowess does not come at the expense of nuance or subtlety, however. Even with the stock tubes, as used here, the emotive, granular, micro-changes in volume, help convey vocal emotion, instrumental stress/texture, and general passion and energy in a piece - at a level not commonly heard in any amplifier. It is not uncommon for tube amplifiers to lose-out here, especially with inexpensive tubes, but ZMF/ampsandsound’s little wonder fully preserves these details and nuances, capturing the most subtle tremolo or vibrato, and the end-result is an enormously engaging and emotionally involving musical rendering.
Commonly, inexpensive-to-mid-tier tube-amplifiers can lack somewhat in speed and transient performance. Indeed, it is not uncommon to find tube-hybrid designs stealing the show here. This is not the case with the Pendant. It is extremely quick. Transients are fast, sharp, with no audible overshoot. String-plucks are immediate and precise. Percussion strikes are, well, striking. The black/white transitions of synthesized/electronic “instruments” are stark yet bold … the best aspects of tubes and solid-state.
Stage presentation is expansive, something often found with good tube amplifiers, with venues rendered in a manner in which their ambience - the low-level echoes, reverberation and even the sense of the air in the space - is both palpable and portray and appropriate sense of scale. One of my favorite tracks for getting a feel for this, due to its simple origins and acoustic nature, is “Mining for Gold” (Cowboy Junkies, “The Trinity Session”). It is not an exaggerated presentation, the stage doesn’t seem larger than life, but is more vivid in how it is delivered such that it becomes a bigger part of the musical whole.
Imaging-wise, elements rendered within this space are holographic in their dimensionality, placement and stability within the audio image. Something easily heard with a track I’ve more recently added to those I’ve previously when assessing imaging, to has been Holly Cole’s “Train Song” (Temptation) - where depth and lateral placement are both precise and easily discerned - rather more easily so with the Pendant than with most solid-state amplification that plays in the same price tier.
While tubes have an impact on the noise level with pure-tube amplifiers, the Pendant was extremely quiet. Via either the Lo-Z or Hi-Z outputs, and using the Vérité as the test headphone, no noise/hum/hiss was apparent in any normal listening scenario, even during silent passages/pauses in the music with the volume cranked up as far I would normally dare listen.
If you turn the amplifier up to its full volume, with no music playing, then you may, depending on your tubes, hear some very low-levelnoise, but that represents a playback level that with actual music would fry your headphones, not to mention your ears, in very short order.
In short, this is just not a concern here unless you have noisy tubes (and those will be noisy in any amplifier).
Tubes & Tube Rolling
The sound of pure tube amps, like the Pendant, are affected to a much greater degree by the tubes they are using than tube-hybrid designs. Where tube changes in a tube-hybrid design tend to be very subtle, with a true tube amplifier they can significantly alter the overall character of the amplifier (for better, or worse). And the more aspects of the design that are tube-based, the more potential there is for changes when tube-rolling.
The Pendant uses three different types of tube - one for rectification in the power supply (EZ81 or 6CA4), one dual-triode (12AX7/ECC83S/7025), 12AT7/ECC81/6201, and 12AY7/ECC82) signal tube for pre-amplification and two pentodes (EL84/6BQ5) for the power stage, giving it more potential for tube-based tweaking than most amplifiers in its class.
The stock set of tubes that comes with the ZMF Pendant (at the time this review is being written) come from “JJ Electronics”, and comprise a pair of EL84s, an ECC83S and an EZ81 - and these were used for the primary review/listening sessions. In addition to providing excellent sound, and a solid base-reference point, they’re also a very nice aesthetic match with the black/red color scheme of the Pendant, and exhibit quite visible glow even in daylight usage.
Small signal and power tubes sometimes exhibit audible sensitivity to common in-home sources of EMI/RFI. This is, in part, due to their smaller metal elements being closer to the ideal antenna length for the emissions of things like WiFi and cellphone signals. Some specific tubes, even with a given family, can be more, or less, sensitive than others.
As a result, it is possible that some tube combinations with the Pendant will require the unit be placed away from WiFi routers, especially high-power models. Cell phones, also, can cause chatter and/or “helicopter chop” sounds if place to close to the unit when running certain tubes.
I thoroughly enjoyed my time with the ZMF Pendant - in fact that’s an understatement … I loved listening with it — and my time with which passed all-too-quickly; I found myself not wanting to give it up when it was time to let someone else get their ears on it. I have missed it progressively more since it departed.
The Pendant does an excellent job of delivering the best aspects of tube-based listening, and indeed the “tube amp experience”, including the ability to usefully affect its sound with different tubes, while leaning more towards accurate, rather than heavily editorialized, rendering.
I would describe the Pendant as being “how you build a pure-tube amplifier, when you want to get the best out of tubes, without ignoring technical competence”.
That’s in contrast to a large number of other tube amplifiers, which seem to be tuned to deliver a sound that is closer to “what people that haven’t spent real time with pure-tube amplifiers think tube amps will sound like” (typically overly laid-back, warm/gooey and/or rolled-off).
As such, this is a real breath of fresh air compared to many of its immediate counterparts.
In common with most pure-tube designs, the Pendant does fair best with higher-impedance headphones (80-100 ohms and up, with my favorite pairings being 300 ohms), though the bias here is not nearly as pronounced as with many other such units, and is minimized further with transformer taps yielding both low and high output impedance.
Ultimately, ZMF’s Pendant offers fantastic performance, extremely engaging and compelling reproduction, serious power and, of course, the “full tube experience” wrapped up in one of the most practically-sized (and priced - even down to the tubes being relatively inexpensive), quality tube-amplifiers I’ve had the pleasure of listening with.
If you’re coming from a solid-state background, the Pendant is a rare treat - true high-end tube amplifier performance at solid-state pricing. And if you’re a current denizen of tube-hybrid world, ZMF’s amplifier will deftly demonstrate how lucid and technically capable a pure-tube amplifier can be, while simultaneously dazzling with its tube-rolled-adaptability - far beyond anything you’ll experience with hybrid designs.
I have often said that the highest praise a reviewer can bestow on a product is to buy one for themselves. And for me, I enjoyed the Pendant so much that the only reason I didn’t purchase one for myself immediately came down to my being about to depart for a multi-year world-tour … and iron-laden full-sized amplifiers, with fragile glass tubes, are not a very good logistical fit. However, the longer I have spent without the Pendant, the more I have missed it, and I have decided to add one to my collection for use at those destinations that will permit it - and the only thing left there now is to work on persuading Zach to build me a custom-wood base for the unit and then place the final order …
A fabulous, compelling, high-value and addictive piece!
If you’re considering a proper tube amplifier, I highly recommend getting your ears on the Pendant. And if you’ve heard other tube amplifiers in the past, and found them to be too laid-back or overly warm/mushy, then the Pendant is very likely to change your opinion of them entirely - and for the better.