Parasound Halo A51 5-Channel Power Amplifier

Bring the Cinematic Experience Home

Add the A51 to your home theater and watch—or listen—everything transform. This five‑channel amp effortlessly boosts your AVR, powering your front and surrounds with clean, room-filling performance that punches well above its price.

Designed by John Curl, the A51 runs high‑bias Class A/AB in a direct‑coupled topology for maximum clarity. It delivers 250 W x5 into 8 Ω (400 W x5 into 4 Ω) with THX Ultra2 certification, fed by a 2.2 kVA toroidal transformer and 164,000 µF of filter capacitance for clean current on demand. Balanced XLR and RCA inputs make it a drop‑in upgrade for any AVR/processor with pre‑outs.

Praised by audiophiles and reviewers alike:

• “Midrange was totally seductive…with music, the A51 radiated sweetness and light. With action films, it rained thunder and lightning.” — Sound & Vision (Barry Willis)
• “Benchmark levels of performance at a reasonable price.” — Home Theater Review
• “More than capable of driving any speaker load…a true winner!” — Audioholics

Specifications:

Power Output - All Channels Driven

250 watts RMS x 5, continuous, 20 Hz - 20 kHz 8Ω
400 watts RMS x 5, continuous, 20 Hz - 20 kHz, 4Ω

Current capacity:
60 amperes peak per channel

Power bandwidth:
5 Hz - 100 kHz, +0/-3 dB at 1 watt

Total harmonic distortion:
< 0.2 % at full power

IM distortion: balanced 16 V rms
< 0.04 %

Slew rate:
> 130 V/µsecond

Dynamic headroom:
> 1.5 dB

Interchannel crosstalk:
> 78 dB at 1 kHz;
> 63 dB at 20 kHz

Input sensitivity:
1 V for 28.28 V, THX Reference Lev

Input impedance:
47 k Ω unbalanced; 94 k Ω balanced

S/N ratio:
112 dB, input shorted, IHF A-weighted

Damping factor:
> 1100 at 20 Hz

Voltage:
110V - 120V

Dimensions:
17-1/2" w x 7-5/8" h x 20" d, 7" h without feet

Net weight: 80 lb.

Features:

• Circuitry designed by legendary John Curl
• THX Ultra2 certified
• High bias Class A/AB operation
• Balanced inputs with discrete circuits and XLR connectors
• Direct Coupled - no capacitors or inductors in signal path
• Complementary MOSFET driver stage and JFET input stage
• 40 beta-matched 15 amp, 60 MHz bipolar output transistors
• 2.2 kVA encapsulated toroid power transformer with independent secondary windings for each channel
• 164,000 μF power supply filter capacitance
• DC Servo and relay protection circuits
• AC present, channel status, high temperature indicators
• Heavy-duty 24k gold-plated 5-way speaker terminals
• Gold-plated RCA input jacks; ground lift switch
• Auto turn-on by 12v trigger or audio signal
• 4u Chassis, carry handles, rack mounting adapter included