Parasound Halo A21+ Stereo Power Amplifier

Description

The Parasound Halo A21+ is a high-current stereo power amplifier with circuitry designed by John Curl, delivering 300W x 2 into 8Ω, 500W x 2 into 4Ω, or 1000W bridged into 8Ω. Its high-bias Class A/AB design, massive toroidal transformer, and direct-coupled signal path deliver full power down to 5Hz with stability into speaker loads as low as 1.5Ω.

Features

• High bias Class A/AB operation with 60A peak current per channel
• Stable with speaker impedance dips to 1.5Ω
• Balanced inputs with discrete circuits
• Direct-coupled signal path with no capacitors or inductors
• DC Servo and relay protection circuits with AC turn-on inrush surge protection
• JFET input stage, MOSFET driver stage, 16 beta-matched 15A/60MHz bipolar output transistors
• 3kVA shielded toroidal transformer with independent windings per channel
• Independent power supplies for input, driver, and output stages
• 108,000µF filter capacitors for the output stages
• Automatic turn-on via 12V trigger or audio sensing
• 4 rack-space chassis with rear carry handles; rack mount hardware included

Specifications

• Power Output (Stereo, 0.1% THD): 300W x 2 @ 8Ω; 500W x 2 @ 4Ω
• Power Output (Bridged, 0.1% THD): 1000W x 1 @ 8Ω (4Ω bridged not recommended)
• Current Capacity: 60A peak per channel
• Slew Rate: >130V/µs
• Frequency Response: 5Hz–100kHz +0/-3dB; 20Hz–20kHz +0/-0.25dB
• THD: <0.1% at full power; <0.03% at typical listening levels
• Interchannel Crosstalk: >80dB @ 1kHz; >70dB @ 20kHz
• Input Impedance: Unbalanced 33kΩ; Balanced 66kΩ (33kΩ per leg)
• Input Sensitivity (28.28V output into 8Ω): 1V unbalanced; 1V per leg balanced
• S/N Ratio: >115dB IHF A-weighted; >110dB unweighted
• Damping Factor: >1100 @ 20Hz
• DC Trigger: +9 to +12Vdc, 5mA
• Audio Trigger: 2–10mV
• IM Distortion: <0.04%
• Total Gain: 29dB
• Power Consumption: 1W standby; 160W idle; 300W typical listening; 1400W maximum
• Dimensions: 17-5/8" W x 7-1/8" H (without feet) x 20" D
• Weight: 39.9 kg