So I've been having a ton of fun just comparing Woo Audio WA23 Luna and the Zähl HM1 as just amps. I honestly cannot pick a favorite and the more I listen the more I am amazed at how compelling the sound they produce are, and yet how much different they are at achieving this. I've mainly been using the Stealth primarily because it is excellent at depicting what any changes to the system adds or subtracts and these two amps drive it to absolute perfection. I am using HM1 in Class A & Servo mode with Stealth, everything set to default settings. On the WA23, I have updated the tubes from stock and use Takatsuki 2A3 and the 274b rectifier. With the stock tubes the HM1 very slightly edges it out in raw technicalities such as detail/resolution, imaging, and clarity. I still think even with stock tubes the WA23 just comes across as a more organic and natural listen, it has more weight and body to notes, a more corporeal and grounded sound. It is really "musical". The HM1 strikes back with just unequivocal control of the headphones it drives with incredible incisiveness. The below are some of my findings:
The HM1 delivers music with an 8K like resolution in all its glory with tons of nuances very readily apparent that might be barely noticeable in other amps. The WA23 takes the same 8K quality and puts a bit of slow motion in it just so you can enjoy the elegance of what you are hearing. Both produce a very vivid sound. The HM1 being like if you apply the "vivid cool" filter and the WA23 as though you applied "vivid warm". HM1 has very defined and clear boundaries around the instruments. It's an absolute stunner for how sharply defined the sonic images are and it places them with pit point accuracy. It takes on a tastefully surgical approach. The realism here is really top notch. The separation on HM1 is again really top tier and the whole musical landscape is very focused. Amazingly, its midrange has a really beguiling quality. With this level of detail HM1 is producing one might expect the midrange to be a bit grating or harsh, but what you actually hear is a sense of ease and effortlessness about them. This is exactly how I want a neutral amplifier to sound. It is now my standard for that. It's not adding any extra warmth or overly polishing anything, just from what I can tell is a faithful and honest rendition of what's there. Therefore, assessing this amp is going to be super reflective of the source gear. Be very mindful of that when you hear of HM1 impressions. It is certainly more transparent than the WA23 in that sense.
WA23 seems like it doesn't need to rely on sharply defined edges to make for realism or convincing sonic images. Instead it achieves this via adding body or weight to the instrument, and coloring inside the boundaries of the instrument with the correct highly saturated timbre, the effect of which is a retina like sound. Recall the advent of "Retina display", the whole idea was that the display had enough pixel density that the human eye was unable to discern individual pixels at a typical viewing distance. The same thing is happening here, but in the audio realm. You know with greater certainty than normal that a piano, or a guitar is playing in front of you. This is relative, but HM1 comes across in comparison like an artist that uses 4B pencil to draw the boundaries of an image and shades it with 2B. The WA23 doesn't even draw the boundaries. Instead it shades the entire structure in 4B and the edges are noticed as a naturally biological byproduct.. It's really cool and I think this makes it sound more natural, it has such an organic and refined approach that I haven't quite experienced elsewhere. This is something that is there in stock format, but more so amplified with the Takatsuki tubes. I go back on forth on which amp I think is more detailed.
Another excellent trait of the HM1 is its unrelenting and unapologetic approach to conveying the energy and impact in the music. You know how a heat map uses a range of colors to visually represent the temperature distribution across a surface, indicating which areas are hot, warm, or cool. Well HM1 is like an Energy map, conveying the low and especially highly impactful areas throughout the sound landscape.. You will notice more than usual the dynamic shifts and impact in the music. One of the amazing things the Grimm MU1 and Tambaqui combo brought to the table was the same retina like sound I described above. Thus, I found myself less analyzing and more so switched focus to the interplay between instruments, that is, trying to get the musical intent. HM1 adds another layer to this with the sheer energy it can impart. Not gonna lie, this can at times be a bit much, but is also true if you go to a live event. HM1 better captures this energy. Interestingly, the WA23 is very much up there with the HM1 on conveying energy, dynamics and impact, it just takes the edge off a little bit because of what I regard as a more natural decay, but the added substantial weight it provides to notes is equally impressive.
The bass on HM1 and WA23 is just insane. Quantity and quality wise they are pretty much on par. With HM1, you get absolute accuracy, definition, detail, and impact in the bass lines. With the WA23, it has more bass weight, is just as agile, and I think the sub-bass is even more forthcoming than the HM1
. The word I keep coming back to on WA23 is organic. Even the bass is organic where as HM1 sounds more analytical in comparison.
Finally, the clarity on both these amps is superb, but is of a different nature. I can only regard HM1 as having an active clarity and the WA23 as having a relaxed clarity. By active clarity for HM1, I mean that with its more enhanced treble, dynamic energy impact, and sharper delineation of sonic images, it creates a sense of clarity that feels like a byproduct. It's as if the clarity is an intentional effect, born from its vibrant and precise sound profile. It activates the natural clarity from the headphone. In contrast, the WA23 offers a different kind of clarity, that as I mentioned can only describe as relaxed. I think this is where some might say it has a blacker background. I think this initial impression video is attempting to get to what I think am hearing:
WA23 doesn't have the same sharpness as the HM1 (do not read this as HM1 is sharp), but it is equally compelling, thanks to its rich, 'retina-like' coloration of sounds and the weight it lends to instruments. The backdrop against which these sounds emerge is more at ease and silent, creating a sense of spaciousness and tranquility that allows the music to unfold in a more natural, unforced manner. The notes also naturally start and decay into this abyss. Music breathes a little more on WA23. Notes don't linger as much on the HM1. This is very readily noticeable using the Stealth where I have called the AMTS as a blackhole sucking it out the typical nasty high frequency peaks. The headphone just sounds super clean and highlights this difference between the two amps very well.
What's really interesting is that for some reason I keep noting or thinking that WA23 is keeping up with the HM1, but really HM1 is the under dog here. WA23 is actually more expensive than the HM1 especially with additional tube upgrades. HM1 is not inexpensive, but it is, and this might sound weird, a decent value proposition, compared to the caliber of amps that it is in leagues with, but especially for the versatility it brings to the table. It is ultimately the best solid state amp I have come across. I am very partial to the WA23 because of the unparalleled refinement and polish it brings to the music without giving up any raw technicalities. Super chuffed to have both.
. It is funny how our mutual acquaintance sold me the HM1 is the guy who also convinced me to try the Kobo K465 haha especially since that amp fits my space really well.
No issue with fullness here. Slam
