Parasound Halo A21+ Stereo Power Amplifier

The Halo A 21+ power amplifier is a pinnacle of power and fidelity

The 21+ has two channels providing 250 watts per channel into 8 Ω, it delivers breathtaking audio performance. The high bias Class A/AB operation ensures accurate and detailed sound reproduction, while the stable operation into 2 Ω loads allows for versatility in speaker configurations. The direct-coupled design, free from capacitors in the signal path, preserves signal integrity and enhances transparency. With balanced XLR and unbalanced RCA inputs and A/B speaker terminals, it offers flexibility and compatibility. Experience pure power and fidelity with the Halo A 21+ power amplifier.

Changes from the original A 21→A 21+

• 250 → 300 Watts (8Ω)
• 400 → 500 Watts (4Ω)
• 750 → 1000 Watts (bridged)
• Filter cap: 88,000 uF → 108,000 uF
• S/N: 112dB → 115 dB
• THD (at full power): 0.2% → 0.1%
• Crosstalk (20kHz): 63dB → 70dB
• Transformer size: 1.2 kVA → 1.3 kVA
• Weight: 60 LB → 71 LB
• Refined Halo cosmetic with aluminum end caps & gold highlights
• Updated rear panel with heavy duty speaker terminals from JC 5
• Upgraded internal gold on gold audio connections
• Updated auto turn on circuit

Features

• 300 watts x 2 @ 8 Ω RMS, both channels driven
• 500 watts x 2 @ 4 Ω RMS, both channels driven
• 1000 watts x 1 @ 8 Ω, in bridged mode
• Circuitry designed by legendary John Curl
• High bias Class A/AB operation
• 60 amperes peak current per channel
• Stable with speaker impedance dips to 1.5 Ω
• Balanced inputs with discrete circuits
• CHK Infinium, custom 5-way speaker binding posts
• Gold-plated RCA input & loop output jacks
• Direct-coupled signal path, no capacitors or inductors
• DC Servo and relay protection circuits
• AC turn-on inrush surge protection with relay bypass
• JFET input stage, MOSFET driver stage
• 16 beta-matched 15 ampere, 60 MHz bipolar output transistors
• 1.3 kVA shielded toroid transformer w/ independent windings for each channel
• Independent power supplies for input stage, driver stage and output stage
• 108,000 µF filter capacitors for output stages
• Full power is rated all the way down to 5Hz for unrestricted low-end bass
• Harris hyper-fast soft-recovery bridge diode rectifiers
• Automatic turn-on by 12 V trigger or audio sensing
• 4 rack space chassis with rear carry handles
• Rack mount hardware is included