The HeadAmp GS-X mini is a fully discrete, Class-A (Actual class A, unlike some other amps which claim to be class A but are not), balanced headphone amplifier.
It has a quite frankly stellar reputation as being an endgame amp for many, and comes in at a price of $1795 for the standard model of $1995 if you wish to upgrade the potentiometer to a DACT stepped attenuator.
Personally I would actually recommend going for the regular potentiometer version. I would prefer a stepped attenuator usually, but the size of the steps here are 3dB which makes it impossible to get any sort of fine control over volume, and it often ends up with one notch being too quiet and the next being too loud.
Overall, I really really like the sound of this amplifier and will be talking more about that in the review.
I’m a bit confused why there are no official THD or other specs given for this amp because it’s actually pretty damn good! Yeah you can get more SINAD if you go for some super feedback based opamp design product. But as far as discrete, and especially true class A stuff goes, this does great.
The internals of the GS-X mini are gorgeous, with a linear power supply and a very neatly laid out design overall.
The outside is rather gorgeous too, and comes in an array of colours for the customer to choose from.
A full video subjective review of this amp is on the way, but for now lets have a look at the measurements.
– Audio Precision APx555 B-Series Analyzer
– Amplifier was warmed up for one hour before testing
– Van Damme Star-Quad shielded SPC XLR cables with Amphenol Connectors
– Neurochrome Dummy Load
– Full reports containing additional data and test configurations are attached
– Exact analyzer/filter configurations for each measurement are detailed in the full reports
– All measurements shown below are taken with a 32 ohm load via balanced output unless otherwise specified
Reports available here:
Dynamic Range (AES17): 110.7dB
Noise: 11.5uV with volume maxed, 9uV at unity gain
Energy usage: ~27w constant from wall
NOTE: I used 4v balanced input to the amp for all measurements. As this is the stepped attenuator model, not potentiometer, it was not possible to get the desired output level to exactly the output level desired. If some of the voltage levels are slightly off, that’s why.
Whilst testing this amp it did perform better in various tests with high impedance loads. So you might find that this amp performs better with dynamics than harder to drive planars. But with 4.5w at 32 ohm, it should still have the juice for most headphones on the market.
But the biggest concern for me was that single ended performance is much worse than balanced. If you are getting this amp, plan to use balanced if possible.
1khz 4v in 4v out 32 Ohm:
1khz 4v in 4v out 300 Ohm:
Distortion is much lower for the high impedance load as with a 32 ohm load the amp is struggling a bit with current delivery. BUT, this is at 4v. I’ve only included these so that they can be compared to reviews on ASR if needed. This is NOT at all a realistic voltage you’d be putting into your headphones.
Let’s have a look at 700mv, which is representative of a decent volume on many fairly hard to drive headphones.
1khz 700mv (Headphone Level) 32 Ohm:
1khz 700mv (Headphone Level) 300 Ohm:
Distortion is way better now, and performance is looking good.
PSU noise seems to be the dominating factor, not harmonic distortion itself. Though we can see that both 2nd and 3rd order harmonics are higher with the 32 ohm load.
Worth noting though that the distortion on single ended looks quite different and nowhere near as good, 700mv for 300ohm load on SE:
On Single-Ended the 2nd order harmonics are much higher than balanced. Additionally one channel seems to have much more harmonic distortion than the other whereas on balanced they’re about the same.
1khz 50mv (IEM Level) 12 Ohm:
THD+N / Frequency (90khz bandwidth):
SINAD/THD+N vs output level:
IMD (SMPTE) vs Output Level:
Crosstalk is lower for a 300Ohm Load:
1khz Square Wave: