In this video I review the Sparkos Gemini, a $995 headphone amplifier that mixes a tube pre stage with Sparkos op-amps. And yes, I know how reviewers get a bad reputation for bias—this time I’m biased because the Gemini genuinely impressed me. It’s not an OTL tube amp, it has real driving power, and it can handle basically everything I threw at it, including HIFIMAN Susvara, without bass distortion. You get both 6.3mm and XLR headphone outputs, but keep in mind: it’s a single-ended amp, so the XLR is not balanced. The big story here is the internal tuning. You can open the case and set gain and bias, and the bias setting controls how much “tube” you hear. In the default low-bias setup I felt the tube influence was too strong, with a bit of that tube vibration and less perfect midrange clarity. Once I switched to high bias (less tube influence), the Gemini sounded closer to solid state—and that’s where it became incredible: gliding smooth, punchy and powerful in the bass, colorful and rich in the midrange, and silky, relaxed in the treble. It’s not the prettiest chassis, but the circuit board inside is one of the cleanest, most beautiful layouts I’ve seen.