This is a review and detailed measurements of the Topping NX1s portable, battery operated headphone amplifier. It is on kind loan from a member. The topping NX1s costs US US $39.90 from Amazon including Prime shipping! It is hard to imagine that is being sold for so little money.
The NX1s comes in a sturdy aluminum enclosure which belies its price point:
The little volume control is a bit hard to rotate given the guard next to it. Given the intended purpose (put in the pocket connected to a phone), it seems like a reasonable compromise.
On the back (not shown) is bass boost and gain buttons. Charging is performed using the USB cable which is convenient. I left it charging overnight and was happy to see the charge light go off so it is not overcharging. I think the specs are 4 hours of charging for 40 hours of playback.
There was no heat generated from the unit.
Headphone Amplifier Audio Measurements
As usual, we start with our dashboard of 1 kHz tone, aspiring for unity gain (2 volts in, 2 volts out):
Wow, this is quite good! Distortion is below audible threshold. Noise which is also very low, sets the SINAD (signal relative to noise+distortion). That puts the NX1s in upper class of headphone amplifiers tested:
Signal to noise ratio is quite excellent as well:
But a bit less so with 50 millivolts output, simulating what you get with sensitive headphones/IEMs:
With its competitors all being desktop headphone amps, this is quite an achievement.
The great story so far diminishes fair bit though with frequency response measurement:
The output must be capacitor coupled with too small of a cap to cause that low frequency drop. Bass boost compensates for it but goes way too far in the frequency response.
Most important test is amount of power relative to distortion and noise. Here it is at 300 Ohms:
Performance in low gain approaches the limit of my analyzer which is great. Alas, high gain doesn't produce more power and simply clips a bit later. This may be good though given that phones have usually much less output than my simulated desktop DAC (2 volts).
The story is the same with 33 ohm load:
These are higher power ratings (naturally) than any dongle.
Output impedance is a bit high at 4.4 ohm but not too high:
Channel imbalance relative to volume control position is typical of analog controls:
Headphone Listening Tests
I started my testing with Sennheiser HD-650 high impedance headphones. High gain was useless with the bass heavily distorting at higher volumes. Again, this is with a desktop DAC driving it. With phones, you will likely use the high gain. In low gain, the distortion went away and there was decent dynamic range. Bass as predicted was a bit anemic. Turning on the bass boost fixed that but it screwed up the sound too much for my taste.
Performance with low impedance Hifiman HE-400i was much better with incredibly good resolution and overall performance in low gain.
Conclusions
The distortion and noise measurements of the Topping NX1s are extremely good and go away beyond its budget pricing. The problem is the drop in bass in frequency response. I played with the EQ in Roon player and managed to compensate for that some. But then you have to be careful to not exceed its maximum power capability.
Overall, the NX1s is an unusual product with shining performance in difficult areas (noise and distortion) but not in the easier areas (frequency response). If Topping could fix the frequency response, it would have a winner on its hand. As it is, I can't give it a recommendation. You can decide with the data presented if you want to use it or not.
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As always, questions, comments, recommendations, etc. are welcome.
Feeling pretty poor after spending so much money on Christmas. Appreciate all you can do to get me out of that by donating generously using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
The NX1s comes in a sturdy aluminum enclosure which belies its price point:
The little volume control is a bit hard to rotate given the guard next to it. Given the intended purpose (put in the pocket connected to a phone), it seems like a reasonable compromise.
On the back (not shown) is bass boost and gain buttons. Charging is performed using the USB cable which is convenient. I left it charging overnight and was happy to see the charge light go off so it is not overcharging. I think the specs are 4 hours of charging for 40 hours of playback.
There was no heat generated from the unit.
Headphone Amplifier Audio Measurements
As usual, we start with our dashboard of 1 kHz tone, aspiring for unity gain (2 volts in, 2 volts out):
Wow, this is quite good! Distortion is below audible threshold. Noise which is also very low, sets the SINAD (signal relative to noise+distortion). That puts the NX1s in upper class of headphone amplifiers tested:
Signal to noise ratio is quite excellent as well:
But a bit less so with 50 millivolts output, simulating what you get with sensitive headphones/IEMs:
With its competitors all being desktop headphone amps, this is quite an achievement.
The great story so far diminishes fair bit though with frequency response measurement:
The output must be capacitor coupled with too small of a cap to cause that low frequency drop. Bass boost compensates for it but goes way too far in the frequency response.
Most important test is amount of power relative to distortion and noise. Here it is at 300 Ohms:
Performance in low gain approaches the limit of my analyzer which is great. Alas, high gain doesn't produce more power and simply clips a bit later. This may be good though given that phones have usually much less output than my simulated desktop DAC (2 volts).
The story is the same with 33 ohm load:
These are higher power ratings (naturally) than any dongle.
Output impedance is a bit high at 4.4 ohm but not too high:
Channel imbalance relative to volume control position is typical of analog controls:
Headphone Listening Tests
I started my testing with Sennheiser HD-650 high impedance headphones. High gain was useless with the bass heavily distorting at higher volumes. Again, this is with a desktop DAC driving it. With phones, you will likely use the high gain. In low gain, the distortion went away and there was decent dynamic range. Bass as predicted was a bit anemic. Turning on the bass boost fixed that but it screwed up the sound too much for my taste.
Performance with low impedance Hifiman HE-400i was much better with incredibly good resolution and overall performance in low gain.
Conclusions
The distortion and noise measurements of the Topping NX1s are extremely good and go away beyond its budget pricing. The problem is the drop in bass in frequency response. I played with the EQ in Roon player and managed to compensate for that some. But then you have to be careful to not exceed its maximum power capability.
Overall, the NX1s is an unusual product with shining performance in difficult areas (noise and distortion) but not in the easier areas (frequency response). If Topping could fix the frequency response, it would have a winner on its hand. As it is, I can't give it a recommendation. You can decide with the data presented if you want to use it or not.
------------
As always, questions, comments, recommendations, etc. are welcome.
Feeling pretty poor after spending so much money on Christmas. Appreciate all you can do to get me out of that by donating generously using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/