This is a review and detailed measurements of the Singxer SA-1 balanced headphone amplifier. It was sent to me by shenzhenaudio.com and costs US $599.
While many desktop products look the same these days, I liked the more stout and positive feeling toggle switches on the SA-1:
Unusual to have a low and high "z" (output impedance) on an amp. This can help with ultra-sensitive IEMs to the extent they have a flat impedance curve.
AC power supply is included which I like:
What I didn't like was gain switches being underneath:
For someone like me that constantly switches headphones, it is unworkable. Fortunately as you see later, high-gain works so well that that low gain may not be needed. I suspect they went this way to minimize PCB path lengths and hence improve noise figure. Performance over functionality!
Singxer SA-1 Measurements
Let's stay with balanced input and output:
Most excellent! Distortion is down to -147 dB. Indeed some amount of mains noise which may be an instrumentation issue is causing SINAD to be only "121" dB. I say only jokingly because it is essentially the best I have ever measured:
If this is a discrete implementation, it is an incredible achievement.
Switching to RCA input and 1/4 unbalanced headphone out, performance drops a bit:
Second harmonic rises a fair bit but it is still well below audibility.
I tried testing with XLR input and 1/4 HP out (measured balanced) and got fair bit of ground loop dropping SINAD by a few dB (not shown). Not sure if this is instrumentation issue or design.
The rest of the tests will be with balanced input and output starting with dynamic range/SNR:
50 mv output is top tier allowing you to have noise-free IEM playback:
Frequency response is of course flat:
Let's test power vs distortion+noise using my optimized test for balanced amps at 300 ohm:
As I hinted, performance is almost the same in low and high gain. It is also exceptionally good. Powerful and transparent.
Switching to 50 ohm, we get slightly less optimized performance above certain power level:
We can see that more clearly as we step through a range of output impedances:
Do the math as I have noted to see if you get the amount of power you need at that impedance before distortion rises. There are other high performance amplifiers that don't have this dependency.
Output impedance is shown both for low and high Z.
Channel matching is very good but odd in that the non-matching aspect is when the volume is at max:
Fortunately where you need matching is at low levels and there, the SA-1 does very well.
Singxer SA-1 Headphone Listening Tests
With my Sennheiser HD-650 and its balanced cable, the SA-1 was able to drive it cleanly to insanely loud levels. I am talking full skull resonances for the 1/10th of a second I could tolerate to push it up there!!!
With Drop Ether CX the amp was able to again get huge amount of loudness. At the limit that I could barely tolerate, I could hear some distortion which sounded like the headphone, not the amp.
Overall performance was superb and incredible dynamics, detail and overall fidelity/transparency.
Conclusions
Clearly the Singxer SA-1 is designed using instrumentation to make sure it delivers extremely low levels of noise and distortion. While our testing is stressful enough to show a slight weakness in driving low impedance headphones, the unit is nevertheless worthy of top of the class designation in my book.
I am happy to recommend the Singxer SA-1 headphone amplifier.
-----------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
While many desktop products look the same these days, I liked the more stout and positive feeling toggle switches on the SA-1:
Unusual to have a low and high "z" (output impedance) on an amp. This can help with ultra-sensitive IEMs to the extent they have a flat impedance curve.
AC power supply is included which I like:
What I didn't like was gain switches being underneath:
For someone like me that constantly switches headphones, it is unworkable. Fortunately as you see later, high-gain works so well that that low gain may not be needed. I suspect they went this way to minimize PCB path lengths and hence improve noise figure. Performance over functionality!
Singxer SA-1 Measurements
Let's stay with balanced input and output:
Most excellent! Distortion is down to -147 dB. Indeed some amount of mains noise which may be an instrumentation issue is causing SINAD to be only "121" dB. I say only jokingly because it is essentially the best I have ever measured:
If this is a discrete implementation, it is an incredible achievement.
Switching to RCA input and 1/4 unbalanced headphone out, performance drops a bit:
Second harmonic rises a fair bit but it is still well below audibility.
I tried testing with XLR input and 1/4 HP out (measured balanced) and got fair bit of ground loop dropping SINAD by a few dB (not shown). Not sure if this is instrumentation issue or design.
The rest of the tests will be with balanced input and output starting with dynamic range/SNR:
50 mv output is top tier allowing you to have noise-free IEM playback:
Frequency response is of course flat:
Let's test power vs distortion+noise using my optimized test for balanced amps at 300 ohm:
As I hinted, performance is almost the same in low and high gain. It is also exceptionally good. Powerful and transparent.
Switching to 50 ohm, we get slightly less optimized performance above certain power level:
We can see that more clearly as we step through a range of output impedances:
Do the math as I have noted to see if you get the amount of power you need at that impedance before distortion rises. There are other high performance amplifiers that don't have this dependency.
Output impedance is shown both for low and high Z.
Channel matching is very good but odd in that the non-matching aspect is when the volume is at max:
Fortunately where you need matching is at low levels and there, the SA-1 does very well.
Singxer SA-1 Headphone Listening Tests
With my Sennheiser HD-650 and its balanced cable, the SA-1 was able to drive it cleanly to insanely loud levels. I am talking full skull resonances for the 1/10th of a second I could tolerate to push it up there!!!
With Drop Ether CX the amp was able to again get huge amount of loudness. At the limit that I could barely tolerate, I could hear some distortion which sounded like the headphone, not the amp.
Overall performance was superb and incredible dynamics, detail and overall fidelity/transparency.
Conclusions
Clearly the Singxer SA-1 is designed using instrumentation to make sure it delivers extremely low levels of noise and distortion. While our testing is stressful enough to show a slight weakness in driving low impedance headphones, the unit is nevertheless worthy of top of the class designation in my book.
I am happy to recommend the Singxer SA-1 headphone amplifier.
-----------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
