Singxer SA-2 Fully Balanced Class A Headphone Amplifier

Singxer SA-2 — Fully Balanced Class A Headphone Amplifier / Preamp

“Pure analog precision meets Class A musical warmth.”

The Singxer SA-2 is a next-generation, fully balanced Class A headphone amplifier and preamplifier, designed as the successor to the renowned SA-1. Featuring a complete circuit redesign, upgraded voltage rails, and a powerful discrete output stage, the SA-2 delivers reference-grade dynamics, ultra-low distortion, and rich, natural tonality. With up to 15W per channel into 20 Ω loads, the SA-2 drives everything from sensitive IEMs to high-impedance, current-hungry headphones with absolute authority.

Main Improvements over SA-1

• Increased Output Power — Boosted from 5.5W (SA-1) to 10W @ 32Ω and 15W @ 20Ω; supports headphones down to 8Ω impedance.
• Optimized Circuit Topology — Reduced output impedance and improved current delivery for enhanced control and low distortion.
• Superior Thermal Management — Uses a copper block and aluminum alloy heat-sink system for better Class A heat dissipation.
• Refined PCB Layout — Redesigned trace routing and DC servo circuitry with GND/LIFT mode switch for improved grounding flexibility.
• Ultra-Low Noise — Achieves sub-microvolt noise floor and black background even with high-sensitivity IEMs.

Technical Highlights

• THD+N (Preamp): -125dB @ 1kHz, A-weighted, 5.2V RMS
• THD+N (Headamp): -117dB @ 1kHz, 32Ω @ 8W, A-weighted
• SNR / DNR: >146dB (A-weighted)
• Frequency Response: 20Hz–80kHz ±0.1dB
• Noise Floor: 500nV RMS (low gain, A-weighted 20–22kHz)
• Fully Discrete Class A Architecture — Four fully independent amplification modules for balanced and single-ended paths.
• Transistor Selection: Uses ROHM low-noise audio transistors and ON Semiconductor 4A output transistors in push-pull parallel configuration.
• Protection: Over-current, overheat, short-circuit, DC, and relay delay protection on startup and shutdown.

Amplification & Gain

• Class A Region:
  • 16Ω Load – up to 0.4W
  • 32Ω Load – up to 0.8W
  • 64Ω Load – up to 1.6W
  • >64Ω – nearly full power in Class A
• Gain Settings:
  • SE In → SE Out: 0dB (Low) / 12.8dB (High)
  • SE In → Balanced Out: 6dB (Low) / 18.8dB (High)
  • Balanced In → SE Out: -6dB (Low) / 6.8dB (High)
  • Balanced In → Balanced Out: 0dB (Low) / 12.8dB (High)
• Input Impedance: SE 33kΩ / Balanced 20kΩ
• Input Sensitivity:
  • Balanced In → Balanced Out: 4.2V RMS (High) / 18V RMS (Low)
  • SE In → Balanced Out: 2.1V RMS (High) / 9V RMS (Low)

Output Power (@ THD+N = 1%)

Output Impedance

• Low-Z Mode: 0.15Ω (balanced) / 1.1Ω (SE)
• High-Z Mode: 10Ω (balanced) / 11Ω (SE)
• Preamp Output Impedance: 150Ω (balanced) / 75Ω (SE)

Connectivity

• Inputs: XLR (balanced) / RCA (single-ended)
• Outputs (Headphone): XLR-4, 4.4mm balanced, 6.35mm single-ended
• Outputs (Preamp): XLR (balanced) / RCA (single-ended)
• Gain Switch, High/Low Impedance Switch, GND/LIFT Toggle

Design & Build

• True analog control with zero digital interference (no MCU)
• Full discrete transistor amplification with multi-stage current drive
• High-current, ultra-low-noise LDO power regulation
• Universal power supply (AC100V–240V), auto-switching
• Thermal management via copper + aluminum hybrid heat sink

Dimensions & Weight

• Chassis: 234mm × 170mm × 46mm (W×D×H)
• Weight: 1.8kg (net) / 2.3kg (packaged)

Package Includes

• SA-2 Headphone Amplifier
• Power Cable (region-specific)
• User Manual
• Warranty Card

Usage Tips: For optimal performance, use balanced input and output. High gain is recommended for large, low-sensitivity headphones. For IEMs or high-sensitivity models, use low gain and Low-Z mode to minimize noise floor.