We met up with Andrew and Alisa, the folks behind Sparkos at the Florida Audio Expo. Not at the show was Lütz, the CEO, a benevolent owner, so long as he gets plenty of treats. I have been wanting to listen to their gear for a while now and this was the perfect opportunity, and they were gracious enough to send me home with a Gemini to Really get a chance to get to know it. The MSRP on the Gemini, as the title would suggest is $995.00 (U.S.) putting it closer to what most would consider affordable for a tube-based headphone amp. The amp does also have line-level outputs meaning you can use it as a tube amp or tube preamp. Other outputs include a 4-pin XLR headphone jack and a 1/4 TRS headphone jack. Inputs are a bit limited as there are only a pair of RCAs. Let’s take a look at how it does in our testing.

Setup

Setup can be fairly simple or something that can take you some time depending on how much of a tinkerer you are. What I mean by that is this amp is built for tube rolling, or swapping out types of tubes if you’re not familiar with the term. On top of that is a user-changeable bias using jumpers inside the amp. On the front, there is also a gain button that will change how much “tube power” is used. If you have a handful of different tubes and want to try all the combinations of settings you can easily spend hours or days testing out different sounds. For those of you who like to just set it and forget it, you have the simplicity of the gain button and a wonderful volume knob. I am a bit of a tinkerer but stuck with the stock tube and bias setting to see how it sounds in factory configuration.

Sound

As a Pre-Amp

I happen to have recently gotten in the Orchard Audio Starkrison Mono Premium amps for review so I thought what better way to test out the pre-outs on the Gemini? I hooked up the Starkrimsons to my Sonus Faber Sonetto V speakers. For the source, I used my Marantz SR7009 as a DAC, sending the signal through the pre-outs to the Gemini which also allowed me to use a subwoofer as well.

I streamed the Peter Cat Recording Co’s Album Bismillah which if you haven’t heard, you need to. They are a band that started in New Delhi around 2010 and have this jazzy indie sound. They would fit in perfectly in any contemporary jazz club while having some aspects of big band as well as ballroom music. Floated By is one of my favorites, with the slow and easygoing melody that could easily be played during a dinner service. The Gemini gave it warmth and dimension that isn’t as present without some tube interaction. The clean and neutral Starkrimsons let the warmth flow through the speakers. Imaging for the band is great as well, allowing me to easily place the various instruments the band uses and giving each the space. Where I think tubes shine the most is vocals and Suryakant Sawhney has a wonderful voice that is reminiscent of the Rat Pack days. The Gemini gives his voice a smoothness and richness, making him seem bolder and more present.

Another great album I played is from The National – First Two Pages of Frakenstein. I have a couple of favorites on this one, both “Alien” and “Once Upon a Poolside” are well-composed songs with dark moody vibes. Again the Gemini Shines with vocals, and by extension the mid-range. Mark Berninger has a great voice as well, and the body of his vocals get a great fullness on the Gemini. The combo of the Gemini and Starkrimisons really gives great detail as well, with transients being clear and small background sounds being part of the total sound instead of missing altogether.

Another song that I really enjoyed on the Gemini was “NYC” by Josh Radnor (yes the actor). The melody is built mostly on an acoustic guitar and the strumming has great texture and detail. As the intro ends and the first chorus starts the drums start creating a foundation and when the kick drum hits you can get a sense of the space and how intimate the recording is, there is almost some of the room sound in the kick. In the bridge, there is some distortion put on Josh’s voice before a solo version of the chorus that makes the solo part stand out and again makes the Gemini stand out with it.

As a Headphone Amp

Switching gears I broke out a couple of different pairs of headphones, the Meze 99 Classics and Beyerdynamic DT990 Pros. What I like about using this pair in listening tests is they are very different-sounding headphones, and they have differing impedances, the 99s are 32Ω and the DT990 Pros are 250Ω. As far as sound, the 99 Classics are wam bass-forward and the DT990 are much more balanced so it’s interesting to see how they pair with different amps. I was a bit worried that the 99 Classics may be too warm to pair with a tube amp, and that may be the case for amps that are fully tube, but with the Gemini, they are pleasant and not overpowering. The DT990 does benefit from some warmth for my preferences so I enjoyed them even more with the Gemini. I was impressed with how well the Gemini powered the DT990 Pros, only requiring me to turn the knob a little over halfway with the tube gain button depressed, with it off I was a bit under halfway up.

I listened to Laufey’s Bewitched with both the 99 Classics and the DT990 Pros and I do think for that style of music I prefer the combo of the DT990 and Gemini as the 99 Classics plus tubes was a touch too warm for her voice. The DT990 can be a little bright as you may see on their response graph they tend to climb at the high end, though fairly flat for the rest of the range so having some warmth added in makes them a very easy set of headphones to listen to. I wish I had a set of Grados in to try with the Gemini to really see how much warmth and body it is capable of adding in. I have found Grados to be a bit thin for my personal tastes, however extremely fast and detailed so if you gave them a bit of low end it would round them out nicely. The DT990 is between the 99 Classics and Grados in tonality, so they don’t need loads of low-end, just a little and the Gemini gives them that.

I changed up the genre and played NF, his album Hope is great, my favorite track being Gone with Julia Michaels. The bass drop before Julia’s part hits pretty hard on a speaker system and the Beyerdynamics just don’t do it justice but with 99 Classics you get a much better sense of the impact. It is a tough balancing act, especially with a song that has the bass and female vocals. I should clarify though, the warmth and tonality of the 99 Classics on female vocals is far from a deal breaker. If I am listening to hip hop or rap I want that bass, and the warmth is ruining vocals, but if I am listening to a jazz album with female vocals, I am going to prefer the DT990s with the Gemini. It’s also worth noting you can get the bass without as much midbass by turning off the tube gain on the 99 Classics, but overall I preferred it on.

Switching it up again I listened to Rage Against the Machine, Battle of LA. This is another scenario in which you aren’t going to find me in the DT990 Pros. Rock, Metal, and the like really need that low-end punch to deliver the energy of the music and the grungey bass-heavy Battle of LA is a perfect example of this. It is worth mentioning that Zack De La Roche’s voice also benefits from the mid-range richness of the 99 Classics. The Drop D tuning RATM uses also benefits from added bass and mid-bass, though not as much as Drop G tuning does to get across the mood and power of the guitar in heavy metal.

One of my favorite parts of headphone hifi is how easy it is to change up my setup depending on my mood. Not only is it much cheaper to have a handful of good headphones than a handful of good speakers, but also much less space-consuming. If I want to play Lil Wayne or Tchaikovsky, I can tune my listening experience to cater to one or the other easily and get the most out of my music. The Gemini is certainly warmer than some of the other full solid-state amps I have played with but it is not so much more mid/bass forward that a brighter headphone can’t bring it back when you want it to. Add in all the actual tuning options you have with the amp itself and you surely can find a combo that sounds perfect to your ears as well. Overall I like bass, I spent the majority of my time with the Gemini listening to the 99 Classics, but was able to enjoy the DT990 Pros as well and more than I typically do.

Pros and Cons

Pros

• Easy to tailor the sound to your liking
• Great tube sound
• balanced output
• can be used as a preamp
• smooth volume knob

Cons

• only one set of analog inputs
• no digital input

Associated Equipment

• Meze 99 Classics
• Beyerdynamic DT990 Pro
• Rotel CD-11 Tribute
• MacBook Air M2
• iPhone 14 Pro
• Orchard Audio Starkrimson Mono Premium
• Sonus Faber Sonetto V

Specs:

Conclusion

For me, the Gemini is the best-sounding tube headphone amplifier under a grand. Sure you can get more feature-rich amp/DAC combos for the price, but not the same level of sound as using the Gemini with a quality DAC. I also don’t know any other tube amp in this market segment with the user customization that the Gemini offers, meaning it is something that you can grow and experiment with for years. The added benefit of using it as a tube pre-amp is just icing on the cake for me. I had fun playing it through my Sonus Fabers and it’s not something you can typically do with a headphone amp. For me the only issue lies in the limited inputs, I would like to see a couple of sets of RCAs giving the pre-amp option a bit more functionality. I don’t mind the lack of a DAC section as there are loads of great DACs to feed this with and not having a DAC competing for circuit board real estate means a cleaner path for the music. It may seem pricey, but I have tried the cheap tube amps, they just aren’t good, and they do not last. Save your money and get the Gemini, which compared to some of the options out there is expensive, not cheap, meaning it has great quality and value at its price point. Spakos used a lot of premium components in this amp and the sum of which makes an incredible product that I could be happy with for years and years to come.

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Disclaimer:
Sparkos Provided Hifi Chciken with a demo unit of the Gemini for the purpose of this review. Sparkos, nor any Affiliate paid in part or full in exchange for this review.