SMSL PA400 Gallium Nitride Power Amplifier

The SMSL PA400 GaN Power Amplifier delivers a rare mix of muscle and nuance. Built around gallium nitride (GaN) power transistors from Infineon, it pushes 600W of clean power while keeping distortion at a mere 0.003%. Pair it with your favorite DAC or preamp and you get detail, control, and effortless dynamics across any speaker system.

The latest gallium nitride power stage

At the heart of the PA400 is Infineon’s GaN power transistor, operating at an ultra-high 1MHz switching frequency. That’s fast enough to keep transients crisp and controlled while preserving low-level detail. The result is full-band precision: bass that feels taught, mids that sound uncolored, and treble that stays smooth even at high volume. With a THD+N of just 0.003% and SNR of 115dB, you’ll hear silence where there should be silence and texture when the music calls for it.

Two modes, two moods

The PA400 can run in stereo balanced mode or XLR mono bridge mode, giving you flexibility depending on your system and space. In stereo, it’s clean, open, and faithful—ideal for reference listening. In mono, two units can work together to quadruple output power, driving demanding floor-standing speakers or large studio monitors with ease. Either way, its linear response and low noise floor keep the signal pure and consistent.

Designed to stay cool and quiet

The PA400’s chassis is carved from aerospace-grade aluminum alloy with precision CNC machining. Those sculpted fins on the side enhance passive heat dissipation, keeping the amp cool even when the evening gets away from you. 

Built to last, built to please

Every detail of the PA400 reflects careful craftsmanship, from the finely-milled control knob that turns with buttery-smooth resistance to the soft rubber feet that absorb vibration and keep the amp stable on your desk or rack. Inside, audiophile-grade components and a dedicated 600W switching power supply deliver stable current to your speakers. Protection circuits guard against overheating and overcurrent, so it performs day in, day out.

Seamless integration

Connecting your system is straightforward. XLR and RCA inputs give you options whether you’re pairing it with a balanced DAC or a vintage line source. Gold-plated binding posts ensure zero-loss signal transfer, and the labeled rear panel makes stereo and bridged configurations clear at a glance. Whether your system includes an SMSL D400 PRO DAC, PL200T CD player, or any high-end preamp, the PA400 plays nicely with all of them.

Product highlights

• GaN power transistors from Infineon
  
• Ultra-low 0.003% THD+N and 115dB SNR
  
• Stereo balanced and mono bridged modes
  
• 600W continuous output at 8Ω/4Ω
  
• Aerospace-grade aluminum chassis with passive cooling
  
• Gold-plated input and output terminals
  
• Audiophile-grade internal components
  
• Overheating and overcurrent protection
  
• XLR and RCA inputs for flexible connectivity
  
• Precision-milled control knob and vibration-damping rubber feet
  

Specs

• Input: Balanced (XLR) / Line in (RCA) / Mono (XLR)
  
• THD+N: 0.003%
  
• SNR: 115dB
  
• Channel separation: 75dB
  
• Input sensitivity (stereo):
  
  • RCA: 0.96Vrms / 22kΩ
    
  • XLR: 2.1Vrms / 22kΩ
    
• Input sensitivity (mono):
  
  • XLR: 2.7Vrms / 22kΩ
    
• Output power (stereo):
  
  • 4Ω: 250Wrms ×2
    
  • 8Ω: 200Wrms ×2
    
• Output power (mono):
  
  • 8Ω: 500Wrms ×1
    
• Standby power: <0.5W
  
• Power consumption: 40W (normal volume)
  
• Dimensions: 10in × 1.88in × 9.53in (254 × 47.7 × 242mm)
  
• Weight: 5.69lbs (2.58kg)
  

What’s included

• SMSL PA400 GaN Power Amplifier
  
• Power cable
  
• User manual