Product Details

SA-2 Fully Balanced Class A Headphone Amplifier / Preamplifier

The newly designed SA-2 is a high-performance, fully balanced, and fully discrete Class A headphone amplifier / preamplifier, created as the natural successor to the acclaimed SA-1.

While the chassis design retains the elegant, understated look of its predecessor, the SA-2’s internal circuitry has been completely re-engineered — delivering dramatically higher output power, lower output impedance, and even greater musical refinement.

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Key Upgrades Over the SA-1

1. Power Output:
    • Increased from 5.5 W @ 32 Ω → 10 W @ 32 Ω (up to 15 W @ 20 Ω).
    • Drives headphones down to 8 Ω minimum impedance.

2. Ultra-Low Distortion:
    • Optimized circuit architecture maintains reference-grade linearity at high power.

3. Thermal Management:
    • Copper block + aluminium alloy heatsink ensures stable Class A operation.

4. Improved Output Stage:
    • Reduced balanced-output impedance for stronger current delivery and superior control.

5. Enhanced Design:
    • Refined PCB layout, DC-servo circuit, and GND/LIFT switch for lower noise and ground-loop isolation.

Global 100–240 V AC operation — identical hardware across all regions (China, EU, US, UK, AU), differing only in supplied power cord.

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Measured Performance

• THD+N (Preamp): –125 dB @ 1 kHz (A-weighted, 5.2 V RMS)

• THD+N (Headphone Out): –117 dB @ 1 kHz (32 Ω @ 8 W)

• Noise Floor: < 0.83 µV RMS (A-weighted 20 Hz–22 kHz)

• SNR / Dynamic Range: > 146 dB (A-weighted)

• Frequency Response: 20 Hz – 80 kHz ± 0.1 dB

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All-Discrete, Fully Balanced Class A Architecture

The SA-2 uses a true quad-channel, all-discrete Class A topology — fully analog with no digital control interference. Differential input pairs employ Rohm ultra-low-noise matched audio transistors, while output stages use multi-stage current amplification with ON Semiconductor power devices delivering up to 4 A drive per channel.

This design achieves the effortless control and composure of a high-power speaker amplifier — revealing every nuance of your music with warmth, space, and natural dynamics.

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Comprehensive Protection

Over-current, overload, overheat, short-circuit, DC protection, power-on delay, and relay-cutoff on shutdown ensure safe, reliable long-term operation.

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Connectivity & Versatility

• Inputs: Balanced (XLR) / Single-ended (RCA) with switchable selection

• Outputs: XLR 4-pin balanced, 4.4 mm balanced, 6.35 mm single-ended

• Preamp Outputs: Balanced (XLR) + Single-ended (RCA)

• Gain Modes: Low for IEMs (virtually silent background) | High for planars & high-impedance headphones

• Output Impedance Modes: Low / High — tailor current drive and tonal character to your headphones

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In Essence

The SA-2 refines every aspect of the original design — more power, lower noise, richer tone.
It’s a true Class A, reference-grade amplifier for both headphone enthusiasts and audiophiles seeking a transparent yet musical preamplifier.

Usage Recommendations and Precautions:
1. As the SA-2 is a fully balanced headphone amplifier optimized for balanced operation, the recommended configuration is: balanced input with balanced output. The secondary recommendation is single-ended input with balanced output.
2. If using single-ended, it is recommended to use single-ended input.
3. For highly sensitive headphones such as earbuds, high-gain mode is not recommended.
4. The ground switch defaults to GND mode. If loop ground noise occurs, switch to LIFT mode (floating ground mode)

 

APX555 Test Performance:

 

 

 

The headphone amplifier's balanced output with a 32-ohm: