So, I've been listening to the GS-X mini for awhile now, and let me just say, it's been an amazing experience. To me, the mini sounds better than the Singxer SA-1, but I have not tried using jumpers to bypass dc protection on the Singxer. As a side note I've learned that the sound does change on the mini depending on its current operating temperature. In my experience, the temperature needs to be in the "Goldilocks zone", neither too hot or too cold, for it to sound its best. I usually have my fan (aircom s6) on low and set on temperature activation.
It's an Immersive sound. Hearts strings being pulled, deeper connections being made, and spirits soaring is what I've come to expect when listening with the GS-X mini and a pair of resolving headphones (in my case it's the Stellia). There is a weight and realism to female vocals (I'm partial to female vocals) that stops me in my tracks... every time, but there's more. Alongside weight and fullness, there is refinement. You hear the vocal textures and nuances, whether it's grit or the delicate decay at the end of a note, in stunning clarity. This of course is dependent on the audio chain, but for me, the gs-x helps make it less about listlessly listening to music, and into more of an experience. I've had the gs-x mini since late May, so the "honeymoon phase" has been long past, but if you couldn't tell, I still very much adore the mini.
The Singxer SA-1 does a lot of things well, and I would have no problems recommending it to anyone interested in a Class A type HP amplifier. In retrospect, if I had to gauge how close the Singxer was to the GS-X mini, I'd say its about 80% of the Mini. That 20% may be enough for some to justify purchasing the Mini and if you can swing it, I'd say do it. But the Singxer has very good price to performance value, especially considering you can make it sound even better by bypassing the DC protection circuit with jumpers.
I wanted to write a more indepth review and comparison on both amps, but to be honest, you're not losing with either amp. They share most of the same merits, albeit the GS-X does everything a little better. I do not see myself replacing the mini for a long time. It's just too convenient not having to swap tubes
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Current setup: Amazon HD -> AQ Diamond USB -> Matrix Spdif 2 (Uptone LPS 1.2) -> RAL i2s cable -> Musician Pegasus R2R (SR Orange fuses) -> Silver Dragon XLR Interconnects -> GS-X Mini (ifi Supanova power cable into wall outlet) -> Moon Audio Black Dragon HP Cable -> Focal Stellia ( I have the computer and Uptone LPS 1.2 connected to a ifi powerstation). Soon to have a Stellar Power Plant 3 and a Zenwave PL-11 cable.