INTRODUCTION
I’ve had the HeadAmp GS-X Mini headphone amplifier on loan for nearly two months, and it’s been anchoring a lot of higher end review work in that span. So, it is time to give it its own write up. A caveat I want all readers to be aware of: this is the first amp in this price range I have any real experience with and writing a review of any piece of gear in a new price tier up is always a challenge; context is lacking. In terms of describing this amp’s place in the market, the best I can do here is comment on what this amp does above and beyond amps up to about $1200. I cannot comment on what it does compared to other amplifiers near it in price. A bonus commentary I can make, though, is how synergy starts to increase in importance as gear gets into this price range (ok, starting a bit lower) and higher. Alright, let’s dive in…
TL;DR
The GS-X Mini is a well-built, powerful, headphone amplifier that has a very no-nonsense honesty about its sound. It has the power to drive just about any headphone and drive it well and the grace to handle very easy loads just as well. With the right headphones its sonic highlights include detail retrieval, macrodynamics, and overall control. Its spatial presentation is on the intimate side and its imaging falls just sort of what many would consider holographic, but overall the Mini is a strong contender at $1800.
FEATURES & BUILD
OK, the name “Mini” is a bit of a misnomer, IMO. While the build is compact, it’s not necessarily small and there is a fair amount of weight here. Yes, there are headphone amplifiers out there that get crazy big and are not desk friendly. This amp isn’t quite that bad, but it has a non-negligible footprint and also needs room to breathe; it gets hot and has ventilation holes all over its top plate. That said, the construction is solid with an all-metal chassis. The front faceplate has a brushed finish and comes in several colors. The one loaned to me is a green that falls somewhere between apple Jolly Rancher and “You wouldn’t like me when I’m angry”:
Unfortunately, the green is discontinued.
The Mini is a fully-balanced amplifier. The back panel has one set each of balanced 3-pin XLR inputs and RCA single-ended inputs as well as a matching complement of pre-outs. The front panel has simple toggle switches for power, gain (hi or lo), headamp or preamp, and XLR or RCA input. The center of the front panel has a large volume knob. In the base configuration, that volume knob is attached to an ALPS RK27 potentiomenter. HeadAmp offers an option of a DACT CT-24 stepped attenuator for $200. The stepped attenuator makes turning the volume knob a clicky experience. The unit I have on loan has that stepped attenuator. There are also balanced 4-pin XLR and ¼” single-ended headphone outputs, as well. The power spec is a bit hard to find but it seems to be in the neighborhood of 4 Wpc from the balanced output. The amplifier is a Class A amp.
KNOW YOUR REVIEWER
My preferred genres are rock/metal and classical/orchestral music. I’m getting to know jazz more and enjoying quite a bit. I also listen to some EDM and hip-hop. My hearing quirks include a high sensitivity to midrange frequencies from just under 1KHz to around 3Khz, give or take. My ears are thus quick to perceive “shoutiness” in headphones in particular. I describe “shoutiness” as an emphasis on the ‘ou’ sound of ‘shout.’ It’s a forwardness in the neighborhood of 1KHz and/or on the first one or two harmonics above it (when I make the sound ‘ooooowwwww’ into a spectrum analyzer the dominant frequency on the vowel sound is around 930Hz, which also means harmonic spikes occur again at around 1860Hz and 2790Hz). In the extreme, it can have the tonal effect of sounding like a vocalist is speaking or singing through a toilet paper tube or cupping their hands over their mouth. It can also give instruments like piano, but especially brass instruments, an added ‘honk’ to their sound. I also get distracted by sibilance, or sharp ‘s’ and ‘t’ sounds that can make ssssingers sssssound like they’re forssssssing esssss ssssssounds aggresssssssively. Sibilance does not physically hurt my ears nearly as quickly as shout, though. It’s distracting because it’s annoying and unnatural. Readers should keep these hearing quirks in mind as they read my descriptions of sound.
SOUND
Test Equipment
DACs used include Holo Audio Spring 2 Level 2, Chord Hugo 2, Schiit Bifrost 2, Soekris dac1321. Headphones used include HiFiMan Arya and Edition X V2 (HexV2), Audeze LCD-2 prefazor (revision 1), Sennheiser HD6XX, Beyerdynamic DT880 600Ω. Those were all rather briefly used. I spent much more time with the foursome of Fostex TH900 with Lawton Purpleheart chambers, Audeze LCD-24, Abyss Diana Phi (DiPhi), and HiFiMan HE1000V2 (HekV2) on this amp.
I listened to the Mini almost exclusively from the balanced headphone output but used both the XLR and RCA inputs. The only difference between the inputs I noticed was the need to adjust the pot for the different input voltages.
General Comment
From the drop, I can say that the Mini was the workhorse over these past two months as I evaluated the 4 high-end/TOTL-ish headphones mentioned in the preceding paragraph and compared the four DACs from the same paragraph. It had the power, control, and detail retrieval necessary to help pick out what made each of those fancy cans tick. That doesn’t mean that all 4 headphones sounded their best on it, just that I quickly grew to trust that the Mini was simply being honest with me about what it saw in the signal because the resolution was always strong. I drop this comment here so that what follows may be considered relative to this reality.
Sound Signature
Picking out a catch-all description of sound signature for this amp – such as ‘warm’ or ‘energetic’ – was a challenge. That’s because synergy matters. The entire sound profile can be audibly different depending on what headphone is plugged into this amp. I think more often that not it comes across as neutral-bright, but know that I am hedging on that quite a bit. I say it because to my ear the upper mid-range and treble regions sounded a bit more emphasized than the lower mids or bass regions. This emphasis varies in degree. Many of my familiar headphones sounded slightly brighter and sharper (“sharp” not necessarily having a bad connotation here) than I am familiar with them sounding. However, this pattern is not immutable. My TH900 Lawtons, built on Fostex’s 1.5T biodynamic driver, can be treble-sharp at times. In fact, you’re just a quick Google search away from reading many accounts of listeners struggling with the aggressive treble of 1.5T-based headphones. On the Mini, they sounded bright and detailed but never sharp or piercing. Similarly, the DiPhi is an aggressively detail-forward headphone at times. The Mini smoothed that out and the treble is again bright and detailed without being sharp or fatiguing. However, more relaxed headphones like the LCD-24 or the HekV2 tended toward more sharpness and could at times be sibilant and piercing on the Mini moreso than the other amps I have on hand to listen with.
The bass, while not emphasized from a frequency-response standpoint, has good punch and texture. The amp sounds very in control, delivering an impactful leading edge with good decay and low frequency detail. Yet, it can still rumble when it needs to. There’s also good bass texture. In my HiFiMan Arya review I mentioned how the Arya was the first headphone to really introduce me to bass texture. The Mini was the amp driving the Arya as it did so.
To my ears the mids didn’t really announce themselves as being a standout or being a weakness. In fact, I noticed transparency in the mids more than anything else. For example, the Mini was able to showcase that the Holo Spring 2 dac is a little smoother yet more present in the mids than the Hugo 2, where the Hugo 2 was a little more laidback in terms of frequency response but more energetic and active in the mids. The difference is very subtle between those two, but the Mini had the chops to show me that difference.
Spatial Presentation
The Mini’s soundstaging is on the intimate side. Fans of big, wide soundstages are not likely to be pleased here. The stage isn’t too small or too cramped, it’s just not expansive and doesn’t always deliver that concert-hall-size of stage that helps with things like symphonies, pipe organ music, or grandiose movie soundtracks. The imaging, separation, and layering within that more intimate stage are solid, but don’t jump out at me as being a huge step up from the $1200 Violectric HPA V200. In my opinion, the intimate soundstage isn’t inherently a problem. It works well for some genres of music and some listeners just like it. I mean, an intimate soundstage has worked just fine for the Sennheiser HD6?? series for 25+ years now. I personally would have liked a bit more holographicity (spell check hates that one, lol) from the imaging, though, especially at $1800-2000.
Detail Retrieval
The resolution of the Mini is one of its standout qualities. It extracts a lot from the music. Texture is one such thing that I mentioned earlier. But that texture isn’t just in the bass. The resinous-ness of bows on strings is resolved beautifully. Any dissonance of an out-of-tune piano is presented. Did that drummer just click the sticks together? Yes, probably. And the Mini doesn’t hide it. This aspect of performance is the main reason I described this amp as my workhorse while evaluating headphones and DACs over the past couple of months. I just got the sense that it told me what was in the signal moreso than the other amps I’ve been working with to this point.
More on Synergy
I mentioned the treble response of various headphones in the Sound Signature subsection. I want to expand on synergy here. The Mini, along with the other high-end pieces I’ve had come in over these first 3 months of 2021 (Spring 2, Hugo 2, HekV2, DiPhi, LCD-24, TH900 Lawton) really drove home the importance of synergy. Those are all really great pieces of gear in their own rights. They don’t all play nicely together, and even if they get along well different combinations bring out or relax different aspects of the sound to greater extents than I’ve heard on entry-level and mid-fi gear. In my LCD-24 review I stated that I preferred that headphone with the Vio V200. The Mini’s aggression didn’t go well with the 24 and it became sharp and sibilant and shouty more than it did on the V200. Similarly with the HekV2. The HekV2 has a midrange recess around 1KHz that makes shout not a problem for me, but it’s already brighter in the treble than the 24 and that got emphasized even more on the Mini than with V200, Monolith Liquid Platinum, or Cayin HA-1Amk2. To my ear the HekV2 also has more low-end punch/slam on the V200 than the Mini. But, that’s the only headphone for which I can say that is true. Every other headphone punched harder on the Mini. Also, headphones that I expected to be more aggressive (TH900, DiPhi) were still very detail-forward but also smoother and more listenable on the Mini than the V200. There are two points to make here: (1) as price of gear goes up synergy becomes increasingly important and (2) if you’re considering buying the Mini you need to do your homework and be very careful what headphones you pair it with. With the Mini, my experience swung from not very enjoyable (HekV2) to meh (LCD-24) to pretty rockin’ (TH900 and DiPhi).
WHAT DO YOU GAIN WITH MINI COMING FROM MID-FI?
I’ve commented on this some throughout the Sound section, but will collect more thoughts here. My go-to personal solid-state amp has been the Violectric HPA V200. The V200 is wider in its soundstaging and right on the heels of the Mini in imaging, separation, and layering. The V200 has a warmer signature that is more headphone-invariant (but not entirely invariant) than the Mini is with its signature. The biggest sonic advantages the Mini has over the V200 are its resolution and timbre. It extracts and presents more detail, and makes things sound just slightly more true-to-life than the V200…when it’s paired with a headphone it gets along with. The Mini is more textured throughout the entire frequency spectrum. The TH900 Lawton and the DiPhi slam a lot harder with the Mini than the V200. Those two probably experience the biggest change in that behavior than any of the other headphones I tried. It’s also worth mentioning that ergonomically the Mini has some real advantages over the V200. The V200 has more gain settings, but they are toggled with dip switches on the back of the unit. The V200 also has both XLR and RCA inputs, but no selector switch at all – it defaults to the RCA input if both are receiving signal. The V200 also lacks a preamp section. So, while the V200 is sonically the closest to the Mini in technical performance in my personal collection, it’s also not nearly as easy to use as the Mini.
Compared to amps under $1000, the Mini is a bigger step up in everything but soundstage size. The size of soundstage isn’t necessarily a sign of quality, it’s more of a preference thing. But in every other technical area, the Mini outclasses my mid-fi amps rather noticeably. Those mid-fi amps include Monolith Liquid Platinum, Lake People G111, and Cayin HA-1Amk2 (tube amp). The one exception to this might be that the Liquid Platinum, especially when paired with the Bifrost 2 and with Amperex PQ Gold Pin tubes in it, can have amazingly natural timbre for the price point. Even so, the Mini has just the slightest of edge in timbre over that combo. Still, outside of that one specific aspect of one specific pairing though, you simply get increased technical proficiency across the board with the Mini.
FINAL THOUGHTS
Do your homework and make sure that whatever headphone(s) you plan to use with the Mini are headphones that the Mini gets along with. Assuming you’ve done that, yes, the Mini is a compelling headphone amplifier. It has excellent resolution and synergizes with some headphones in special ways that should be strongly considered if you’re shopping for an amp in this price range. It also comes in an attractive, well-built, and easy-to-use package. I will appreciate this amp for a long time because of what it has taught me about this hobby. I will miss it when its gone.
Thanks for reading, all. And enjoy the music! 
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