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Topping NX3s Portable Amplifier


Powerful headphone amp

Topping NX3s is an ideal partner for your smartphone or DAP. It was designed to drive headphones, earphones and IEMs with low levels of distortion and noise. It significantly improves the output power of its predecessor, the NX3, with 545mW at 32ohms it is able to drive even the most demanding circumaural headphones. The front panel has two switches, one for gain and one for bass boost, which allows easy switching between their settings.

NX3s is built using high quality components, including OPA2140 and LME49720 operational amplifiers by Texas Instruments (the latter is installed in a DIP8 bracket, allowing the user for an easy swap to get a different sound signature), WIMA capacitors and ALPS potentiometer.

TI OPA2140 is a low-power JFET input amplifier that features good drift and low input bias current. The OPA2140 achieves 11-MHz unity-gain bandwidth and 20-V/µs slew rate while consuming only 1.8 mA (typical) of quiescent current. It features rail-to-rail output swing, low noise and very low offset and offset drift. Thanks to these specs, OPA2140 delivers a crisp, high fidelity sound with no distortions and background noise.

TI LME49720 is a ultra-low distortion, low noise, high slew rate operational amplifier optimized and fully specified for high performance. Combining advanced leading-edge process technology with state-of-the-art circuit design, the LME49720 audio operational amplifier delivers superior audio signal amplification for outstanding audio performance. The LME49720 combines extremely low voltage noise density (2.7nV/√Hz) with vanishingly low THD+N (0.00003%) to easily satisfy the most demanding audio applications. But if that’s not enough or a user is seeking different sound signature, the LME49720 is conveniently installed in a DIP8 bracket and can be easily swapped.

Thanks to these components NX3s THD+N is less than 0.0017% at 1kHz for an output of 273MW at 300Ω or less than 0.0003% at 1kHz for an output of 50mW at 32Ω. The noise level is less than 2.5µVrms with the gain set to “low” or less than 6.5µVrms with a gain set to “high”. Finally, the SNR is higher than 120dB. These specs ensure a precise, rich and clean amplification of a wide range of headphones and earphones.

Optional bass boost and gain setting switches additionally increase NX3s versatility and allow the user to alter the sound signature of their system and drive anything from low-impedance earbuds to full-sized, power-hungry planar magnetic headphones.

NX3s is fitted with a 2400mAh battery that allows for at least 18 hours of music on one charge, and full charge takes only 4 hours. NX3s design is clean, intuitive and user friendly. Its anodized aluminum body feels solid and the volume knob has been designed in a way that minimizes the risk of unintentional sound level adjustments.


  • Housing: Aluminum
  • Frequency response: 20Hz – 200kHz
  • Output power: 545mW x 2 (@ 32ohm), 100mW x 2 (@ 300ohm)
  • Suitable headphone impedance: 16 – 300ohm
  • THD+N: <0.0017%
  • SNR: >120dB
  • Noise: <2.5trV (low gain) <6.5trV (high gain)
  • Gain: 0dB / 8.8dB
  • Bass: 0dB / 4.0dB
  • Work time on a single charge: 18h
  • Charging time: <4h @ 1A
  • Charging port: MicroUSB
  • Dimensions: 10.7 x 6.6 x 1.36cm
  • Weight: 157g

Customer Reviews

Based on 1 review
Portable amplifier

Perfect one for my m50x. Thnks to gears for ears