It worked fine with IEMs when we tried it.
Noise floor is extremely low.
Only thing is that @DanMellinger noticed that there would be a small amount of hum present with some IEMs if you placed the transformer box directly ontop of the main unit, but when off to the side it was fine
Yes, just got word they cleared customs last night from UPS. Because of the value of goods there was extra paperwork needed to get everything going.
It does look like there is a possibility that they are delivered to our warehouse today though!
That last icon means out for delivery right? 
Just received the FedEx notification and had to take a moment to catch my breath…
Really nice of you to keep everyone updated here. Pretty exciting for ZAHL owners.
Yeah, it’s weird how excited I am for them!!! and jealous lol
Tried it at Canjam and it is incredible!!
You’re having Envy already? 
No FOMO allowed!
Seriously, it would be end-game for sure (and end of the world for me financially! 
)
Yes , ok fine. It is cool though. I would like to hear it in a quiet space and tinker with the features… which I couldn’t get a good sense of at all at the show.
I will live vicariously through others testimonies of its glory….waiting to seeing some more reviews of it!!
Well, thanks to the reliably amazing customer service from @taronlissimore and headphones.com, my Zähl HM1 arrived (all the way from WA to sunny Florida), this morning!
Just a quick picture for now … where I’d just unboxed it and was letting it come to the same temperature of the room before hooking it all up.
(It’s not actually going to be driven by the Chord stack that’s behind it; I’m be feeding it from the latest-generation Linn Klimax DSM w/ Organik DAC).
…
I’ll start posting impressions as I get more listening time in with the thing; so far I’ve only had about two hours with it … both listening and playing around.
But what I will say right now is that initial impressions are that the HM1 has absolutely been worth the wait. Even fresh out of the box, and just-powered up, it sounds fantastic! I had pretty high expectations for this thing, and it’s easily meeting and beating them.
I am not going to be getting much sleep this weekend …
… more to come …
When you can of course. I’d love to hear about your experiences with the Crossfeed shelf roll off filtering the ZAHL has. Pretty neat feature.
It’s difficult to know where to start with impressions, there is so much initial standout greatness here. I say that based on a bit over seven hours of continuous listening time; during which I’ve become progressively more enamored with the HM1.
Mesmerized.
That’s an appropriate adjective here.
Utterly mesmerized.
Things I would normally only notice in highly focused audition-style listening, are laid bare – with absolutely no concentration required to hear them.
Tonality is utterly neutral. Timbre is the closest to that of a live, natural, acoustic I’ve heard on conventional headphones. Textural nuances and micro-details are easily resolved. Listening across a variety of TOTL/flagship headphones, it’s clear any limitations in replay lay with the cans, not the amplifier.
If you want something other than pure neutrality here, you’ll need to engage the “Sound Adjustments”. But I’ll talk more about those in a later post; since other than playing with them to see that a) they’re clearly audible and b) they’re more agreeable than similar features on other amplifiers, so far, my “proper” listening has been done in “Direct” mode.
Overall presentation is set against an ultra-silent background, which serves to make every aspect of the music seem particularly vivid. How silent? Uncannily so. Almost as stark a contrast as that of stepping into a sub-0 dB anechoic chamber (do it if you ever get the chance … it’s freaky).
There’s a definite and pronounced holographic sense to the rendering the HM1 yields. That’s normally more of a tube-amp thing. That aside, there is nothing tube-like about the Zähl’s delivery; if a tube-like performance is what you want look elsewhere.
Anyway, not to be a tease … more about sound in a while … suffice it to say that that aspect is just amazing to this point.
It’s worth noting that the unit runs warm. It is class-A after all. It’s just warm, not hot (you can easily keep your hands on the thing, even after hours of spirited listening). I’ll do some FLIR shots of the thing once my FLIR camera has recharged. For contrast, it runs noticeably cooler than, say, an RME ADI-2 Pro FS BE. And while it’s warm, it is not throwing off a lot of heat (there’s a difference between temperature and heat …).
No issues or niggles, and absolutely no hint of listening fatigue at all so far. Usually, if there were going to be post initial “wow-moment” issues, they’d have at least started becoming apparent by now … but no … no negatives at all to this point.
Will do.
I’ve only spent a few minutes fiddling with the “Sound Base” (which is what you’re talking about) and “Sound Adjustment” features. Enough to know they make a difference, don’t negatively effect performance, and that the “Sound Base” functionality is different to typical crossfeed implementations.
I imagine I’ll start getting into that stuff sometime tomorrow …
Here’s a quick, decidedly non-glamour, shot of the HM1 in use …
Right now it is setup with input A taking an XLR feed from my Linn Klimax DSM (Organik), and input B coming off the RME ADI-2 Pro FS R BE. I’m using the mixing function here so the RME unit can deal with all the output from my main workstation, and the music is coming from the Linn.
No way to do this with a conventional amplifier. You’d either have to route all the audio via the computer, and it’s internal software mixer, to a single input, or use an external interface/mixer to do the job (non-professional mixers not being known for attention to fidelity).
I should say, that for my listening so far, I’ve had input B switched off … and that’s how it will be used for critical listening. This was just a quick test. But it’s nice to see that using the mixing function really doesn’t impact the fidelity of a single input channel.
I’ve had my HM1 powered up, and running, for a bit more than a full day now. Being class A, it should be drawing the same amount of power regardless of whether it is doing anything or not (or, at least, variances are not from the amplification stages).
Temperature
Peak surface temperature of the unit is 105℉, with the front panel being at 99℉, as measured in a room that’s at 72℉. Total heat output is about 40W at idle (it’ll be a bit lower driving headphones, as some of that energy will be dissipated in the transducer rather than just output as heat). So putting your hand on the unit, you can feel that it’s warm, but hold it an inch away and you can’t tell at all.
Class A vs. Class A & Servo
Most of yesterday’s (and last night’s) listening was done in “Class A” mode. Today I’ve been in “Class A & Servo” (the “servo” refers to a negative-feedback implementation) mode. Transparency and resolution both increase audibly in this mode, which is hard to imagine given how it sounds in plain “Class A” mode.
The HM1 does not become dry, sterile nor clinical in servo mode. The “weight” of its delivery isn’t changed (still gobs of impact, punch and slam). Nor is causing even a hint of listening fatigue; and I’ve been listening for about seven straight hours in servo mode.
The trade-off is a hair less “meat on the bones” vs. simple “Class A” mode. I do mean a hair. The increase in transparency/resolution is much more apparent than the very small and subtle shift in perceived density.
You can tell the difference simply by switching between modes, though the switch isn’t instant. When you turn the mode nob, relays switch out the amplifier stage, the Zähl logo goes out, a second later the logo comes back on, the relays switch back, and sound is restored (at the same output level; there’s no apparent level shift between modes).
Sound Adjustment
When enabled, these apply subtle lift/cut to the bass and treble regions. The steps are audibly different, but seem to affect their respective sonic regions in a more “complete” and “pleasing” manner than similar controls on other amplifiers. The range of adjustment is quite small; even on their maximum lift/cut settings, they’re not fundamentally changing the character of the amplifier. I could happily listen with the bass lift at full, where as with something like the Pro iCAN … anything past the first step is too much and has negative impacts elsewhere.
In “servo” mode, I found that simply engaging one step of bass lift, and one step of treble cut was enough to restore any lost “meat” vs. simple “class A” mode.
Power/Drive
This thing just seems to shrug off whatever load you present it with.
I borrowed a friend’s set of Susvara (recent build) to play with here. The HM1 drives them easily, with more than 30 dB of headroom vs. my normal ~84 dB/SPL listening level.
I think this is the best I’ve heard the Susvara … and over a couple of years I’ve tried them with all of the “high-end” recommendations (including speakers amps well to the high-side of $500K). The HM1, despite being entirely neutral, was somehow even able to lessen the sensation of “limpness” in terms of bass and slam that I find with all of HiFi Man’s cans (excepting the HE6 and HE-500 variants).
If the HM1 could also make the Susvara look and feel less like they were cobbled together in a shed, using the cheapest materials possible, I might have finally had to have sucked it up and bought a pair. Alas, the HM1 is merely an amplifier. A superlative amplifier, to be sure. But an amplifier nonetheless. Whereas the level of transformation I’d want on the build of the Susvara would require a magician or wizard …
…
Proper sound impressions will start to follow from here …
Great notes. Mine doesn’t get here until tomorrow night so I will be using your experiences to guide my humble endeavors. Glad this was worth the wait. Please keep up the impressions and any hints on use always appreciated.
Thanks for the impressions.
If you plug in an easy to drive headphone (I’m not sure if you still own a Focal Stellia or Utopia), is there enough usable range on the volume knob?
That was an issue with a couple of high-powered amps that I’ve tried, where they were perfect for something like a Susvara, but when I tried plugging in my Focal Stellia, I had limited range on the volume knob.
I still own both.
How much range you’ll have is going to depend somewhat on your source and, of course, your listening levels. Coming off a DAC with its output set to the consumer standard levels (~2.2V RCA/~4.4V XLR) I have about half the rotation of the dial to play with for the Stellia and Utopia.
That’s plenty for me.
If I wanted more range, I’d stuck a couple of passive attenuators between the source and the HM1. They’re inexpensive and transparent (their only contribution would be Johnson noise, at somewhere down around -140 dB).
…
The HM1 sounds magical with the Utopia and the Stellia. Really exploits their dynamics too. Super-explosive. Even then, still no fatigue at all (been listening for almost 12 hours today) … even with some rather “spirited” playing of “Above and Beyond” albums.
It’s hard to say, and not just because I’ve really not done anything with it.
Short of using the HM1 to feed another headphone amplifier, firing up my Chord gear again (to drive the Étude or Ultima 5 and SR1a) or running it into my Linn Klimax DSM (which means going through the ADC on that unit, and then through the speaker’s DACs and amps), I don’t have a useful way to evaluate it.
It’ll be a while before I get to doing anything like that; probably not this side of January.
Sorry …
