Zapco - ST-6X SQ III - Class AB, 6-Ch, SQ Power 2Ω: 6 x 150W, 4Ω: 6 x 100W

The Zapco ST-6X SQ III is a 6-channel Class AB amplifier built for true audiophile sound reproduction and system flexibility. Delivering 150 watts RMS per channel at 2 ohms, it’s ideal for active 3-way front stages or full-system amplification where balance, warmth, and precision are critical. With independent crossovers, ultra-low distortion, and Zapco’s legendary analog design, the ST-6X SQ III provides exceptional clarity, dynamic range, and headroom—perfect for sound quality (SQ) competition or high-end daily audio setups. 

• Model: ST-6X SQ III
• Type: Class AB 6-Channel Full-Range Sound Quality Amplifier
• Power Output (RMS):
 • 4 Ω Stereo: 6 × 100 W
 • 2 Ω Stereo: 6 × 150 W
 • 4 Ω Bridged: 3 × 300 W
• Frequency Response: 10 Hz – 30 kHz (±1 dB)
• Signal-to-Noise Ratio: > 100 dB
• THD + N: < 0.05% at rated power
• Damping Factor: > 200 @ 100 Hz
• Input Sensitivity: 0.2 V – 8 V (variable)
• Input Impedance: 20 kΩ (balanced) / 10 kΩ (unbalanced)
• Crossover Network (per channel pair):
 • High-Pass Filter (HPF): 15 Hz – 4 kHz (12 dB/octave)
 • Low-Pass Filter (LPF): 30 Hz – 4 kHz (12 dB/octave)
 • Band-pass configuration possible
• Bass Boost: 0 – 12 dB @ 45 Hz (adjustable)
• Cooling System: Heavy-duty aluminum heatsink with smart thermal management
• Protection Circuits:
 • Thermal overload
 • Short circuit
 • DC offset
 • Over/under voltage
• Fuse Rating: 3 × 40 A
• Power Supply: Regulated MOSFET PWM power supply
• Dimensions: 18.5″ (L) × 7.5″ (W) × 2.2″ (H)
• Weight: Approx. 12.8 lb (5.8 kg)
• Included Accessories: Mounting hardware, user manual