Uncompromising Audiophile Performance

THX Ultra 2 certification ensures movie-house quality sonics, but the Halo surpasses this critical benchmark by delivering Parasound-quality sound derived from the ultra-high-end Parasound JC-1 400-watt mono amp. Matched JFET inputs, MOSFET drivers, and high-current bipolar outputs contribute to its exceptional performance.

Class A / AB Operation and Impressive Firepower

The A 51 boasts balanced inputs with discrete circuits and XLR connectors. Beautifully implemented high-bias Class A / AB operation makes the most of an impressive 250-watt-per-channel power output at 8 ohms and 400-watts-per-channel at 4 ohms. The 2.2 kVA encapsulated toroidal power transformer with independent secondary windings for each channel and 164,000 µF power supply filter capacitance delivers an impressive current capacity of 60 amps per channel. The direct-coupled design uses no capacitors or inductors in signal path. The complementary MOSFET driver stage relies on the firepower of 40 beta-matched 15 amp, 60 MHz bipolar output transistors and works in combination with a JFET input stage.

"Instant" Warm-up Feature

Like all the other amps in the Halo product series, the A 51 has Parasound's exclusive bias circuit, which permits the amplifier to sound perfect from the instant it's turned on, rather than having to wait for bias to gradually build up as the amp warms up over time. Very high bias allows greater Class operating range than others. Even Halo's implementation of its automatic turn-on feature is exceptional. Special relays bypass the AC "soft start" circuitry after it's done its job for the purest AC and the purest sound.

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

Parasound A51 Halo Amplifier User's Manual

Specifications

Continuous Power Output:
250 watts RMS x 5, 20 Hz - 20 kHz, 8 Ω, all channels driven
400 watts RMS x 5, 20 Hz - 20 kHz, 4 Ω, all channels driven

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.

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