This is the third in a series of four posts looking at (what I call) ‘mainstream high-end’ headphone amplifiers. In the previous two instalments, we covered the Pro-Ject Head Box DS2 B (with its optional power supply) and the SparkoS Labs Aries. Today we take a deeper dive on the ZMF Pendant.
Zach Merhbach got his start building acoustic guitars over 15 years ago, which led to tinkering with headphone modifications and eventually the launch of his own company, ZMF. While ZMF has grown considerably more popular in recent years, they remain relatively obscure compared to the Sennheisers and Grados of the world. Headphone fiends will certainly know of ZMF but speaker-oriented audiophiles may not be familiar with the brand.
Merhbach describes his operation as “…based near Chicago Illinois. I have a small workshop and each set is made to order, specifically for each customer. You can think of us as your local farmers market type of headphone builder or a small instrument building workshop who values its customers and makes an extremely high-quality artisan product. Our goal is to make the best sounding headphones for the best price possible. Cater to each person’s needs, as each headphone is made for a specific individual, and careful attention is paid to requests, for no extra charge, unless a material cost is required. Above all, we take pride in what we do, and want to make sure each headphone lasts its current owner a lifetime.”
ZMF is not an amplifier company so they partnered with the similarly artisanal Ampsandsound to build a headphone amplifier to their specifications. This collaboration birthed the ZMF Pendant (US$1999) – an amplifier designed to extract superb performance from ZMF headphones…or any other brand for that matter.
The ZMF Pendant is what I’d call a very ‘traditional’ single-ended tube amplifier design running in ultra-linear mode. It features EL84 driver tubes, an input stage based around the 12AX7 family, and tube rectification in the form of a 6CA4. Prominent top-mounted output transformers sit uncovered to show this is not an OTL design like the Feliks Audio Echo from my Starting Points roundup. The Pendant has RCA outputs for pre-amplifier functionality, dual 6.35mm headphone jacks for low and high impedance connections, and can dump two-and-a-half Watts per channel into 300 Ohm loads.
Setting the Pendant up on my audio console, I was struck by its robust build quality and bold appearance. My review unit came with the US$300 custom wood trim upgrade (elm burl in this case) but even the standard black option looks great to these eyes. It’s most definitely a throwback to classic tube-based designs, and I (surprisingly) even enjoyed having top-mounted jacks for all connections. This is certainly an amplifier that makes a visual statement.
I began with the standard configuration of new production JJ tubes all around. ZMF will include a vintage tube array of their choosing for US$200 extra, but I wanted to get a feel for the baseline performance prior to messing with upgrades.
And what an enjoyable performance it is. The Pendant has a beautiful tone – somewhat warm, spacious, with lovely midrange body and abundant top-end air. In one sense we could call it a “classic tube sound”, yet it manages to avoid many of the clichéd pitfalls commonly associated with tubes. It’s not slow or syrupy. It doesn’t suffer indistinct bass texture. It’s not overly dark, and won’t gloss over detail, but neither does it have any treble etch. There’s a sense of immediacy which suits guitars and vocals particularly well.
This engaging sound, paired with oodles of power and an extremely quiet background, makes the Pendant deployable across many music genres and headphone pairings. Whether playing Mitch Murder’s synthwave classic Current Events via the Focal Clear, the 1973 funk-jazz classic Spectrum by Jimmy Cobham via Meze’s Empyrean, or using the Sennheiser HD800S to browse Crooked Still’s catalog of progressive bluegrass, the Pendant never feels anything less than confident. It’s not the type of tube-y signature which covers up flaws but rather a “makes the most of what we have” – by accentuating the good, it makes one less mindful of the bad.
Compared to the Pro-Ject Head Box setup, I hear some similarities but also several key areas of difference. Both have excellent low-frequency articulation and both offer an extremely quiet background – traits which are welcome in both cases but more expected from the solid-state design than the tubed ZMF offering. The Pendant is a bit warmer and more full-bodied, but – less expected by tube cliché – also sounds faster and gives us a more insightful treble. The net effect of these differences has the Pendant sounding more intense and dynamic, whilst the Pro-Ject stack is comparatively a bit more laid-back and duller – which is not a word I would ever use listening to the Head Box combo in isolation. It’s just that the Pendant sounds more alive.
Tube rolling obviously creates the opportunity to tweak the Pendant to one’s particular system and taste. My tube stash isn’t what it used to be, but I was able to swap out the JJ EL84 driver tubes for a matched pair of late 1950’s Amperex Bugle Boys. This brought a modest improvement to midrange clarity and also seemed to open up the presentation beyond the boundaries of the stock tubes.
I then swapped in a vintage Raytheon Blackplate 12AU7 for the input stage which caused a more drastic change to the Pendant’s sound. Tonality was lighter, treble more spotlit and even faster, with a subsequent reduction in low-end impact. Also noteworthy is how the choice of input tube dictates gain, with 12AU7 being low, 12AT7 medium, and 12AX7 high. My Raytheon 12AU7 gave quite a bit more versatility with sensitive headphones and even in-ear monitors, while the stock JJ 12AX7 was better suited for difficult planar magnetic headphones. I didn’t have a 12AT7 on hand but that may end up being the sweet spot for users who own a large variety of headphones. I did not have a chance to swap out the rectifier tube but that’s yet another avenue Pendant owners could take in their pursuit of an altered state.
When browsing reviews of excellent solid-state amplifiers, I sometimes notice them being described as having a tube-like quality in certain respects. As if a “tube sound” should be the ultimate end goal (And that it’s a singular sound, which it isn’t – Ed). I’m not sure I completely agree with that assessment, but I do understand the sentiment. The ZMF Pendant inverts this thinking – a classic tube design which manages to incorporate many strengths typically associated with solid-state offerings. As such, I think it will really appeal to listeners who want an insightful, fast, punchy sound which offers a rich tube warmth yet doesn’t sacrifice noise floor or low-frequency articulation. Add in the ability to tailor the sound via tube-rolling, plus the amplifier’s throwback aesthetic, and the Pendant comes out looking like a very compelling option.
Further information: ZMF
Next up, the Cayin HA-6A.
For this evaluation, I set up a very high-performance system capable of taking even the best headphone amplifiers to their limits.
The foundation was laid using the Equi=Core 1800 (US$2199) balanced power conditioner and Audio Art power1 ePlus AC cables feeding every component. My transport setup is a bit ridiculous yet totally worth the trouble. It starts with a Euphony Summus (US$2599) music server augmented by a Keces P8 (US$699) ultra-low noise linear power supply. An iFi Gemini 3.0 USB cable splits power and data legs as they travel to a Matrix X SPDIF 2 DDC (US$379) powered by a Wyred4Sound PS-1 linear PSU (US$499). Finally, signals are routed to a Titans Audio Lab Helen (US$1699) for additional jitter/noise reduction, and then off to a Wyred4Sound 10th Anniversary DAC (US$4499) for D-to-A duties. Aside from the iFi USB leash, Audio Art’s e-series cables handle all digital and analog connections.
Headphones run the full gamut from classic Sennheiser HD650 and AKG K701 to modern flagships like HiFiMAN’s Susvara and the Meze Empyrean. The ubiquitous Sennheiser HD800 and Focal Utopia both make appearances, as do lesser-known gems such as the Kennerton Audio Thekk and Audeze LCD-24 Limited Edition. I also didn’t shy away from trying sensitive in-ear monitors ranging from the sensibly-priced Campfire Audio Comet to top-of-the-line 64 Audio A18t customs, and many models in between.