Parasound Halo A 31 Three Channel Power Amplifier

It Holds Nothing Back in Power or Performance

The Parasound Halo A 31 was designed in response to increasing demand for a three-channel power amplifier that holds nothing back in power or performance. The A 31 is identical in performance and sound to the award- winning Halo A 51.

Lots of Application Versatility

You'll find lots of uses for the three-channel A 31. It's fantastic for powering the front three channels of a home theater. The surround or back channels can then be powered by a smaller two-channel Parasound power amplifier, such as the Halo A 23. This gives the greatest power to the front channels where it is needed the most.

You might also want to use the A 31 to power the center channel and two surround channels of your home theater. This allows the left and right front speakers to be powered by a dedicated two-channel power amp, such as the Halo A 21, or better yet, two JC 1 monoblock amps. This is ideal for the music lover who is unwilling to compromise stereo reproduction.

Here's one more suggestion. Use the A 31 to power the front three channels in an AV receiver-based system. The remaining surround and back channels can be driven by the receiver. This assures you of the best sound for the front channels while enabling the receiver to produce more power for the surround and back channels.

However you employ the A 31, you will be delighted by its impeccable sonics, striking authority, and faithful reproduction of the smallest details.

"Impeccably Built and Beautiful"

"The Halo A 31 is able to drive any speaker you are going to throw at it and not complain, as well as being impeccably built and beautiful in appearance," notes Chris Heinonen in his December 5, 2012 review for Secrets of Home Theater and High Fidelity. "In fact, it performed so well I let Parasound know I'll be paying for it and keeping it as my reference amp going forward."

Raw Power Plus Elegant Circuit Design

The three-channel Halo A 31 power amplifier combines raw power with elegant circuit design. Designed by legendary audio guru John Curl, the Halo brings uncompromising audiophile performance to home theater.

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. It has adjustable gain for up to +6 db over THX Reference level. Matched JFET inputs, MOSFET drivers, and high-current bipolar outputs contribute to its exceptional performance.

Class A/AB Operation and Impressive Firepower

The A 31 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 1.5 kVA encapsulated toroidal power transformer with independent secondary windings for each channel and 98,400 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 24 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 A51 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.

And That's Not All…

AC present, channel status, and high temperature indicators team up with DC Servo and relay protection circuits to keep this powerhouse running safely at peak performance for years of reliable service. Auto turn-on by 12-volt trigger or audio signal simplifies home theater and multi-room operation. Other features include heavy-duty 24k gold-plated 5-way speaker terminals, gold-plated RCA input jacks, and a rear-panel ground lift switch.

Product Features

250 watts x 3 @ 8 Ohms / 400 watts x 3 @ 4 Ohms
Adjustable gain for up to +6db over THX Reference level
Unbalanced RCA and balanced XLR inputs
Circuitry designed by legendary John Curl
High bias class A/AB operation
Direct coupled (no capacitors or inductors in signal path)
Complementary MOSFET driver stage and JFET input stage
24 beta-matched 15 amp, 60 MHz bipolar output transistors
1.5 kVA encapsulated toroid power transformer with independent secondary windings for each channel
98,400 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
THX Ultra2 certified
Auto turn-on by 12v trigger or audio signal
4u Chassis, carry handles, rack mounting adapter included
Parasound 5 year parts, 5 years labor warranty (USA purchases only)

Product Specs

Power Output - All Channels Driven

250 watts RMS x 3, continuous, 20 Hz - 20 kHz, 8Ω
400 watts RMS x 3, continuous, 20 Hz - 20 kHz, 4Ω

Current Capacity

60 amperes peak per channel

Slew Rate

> 130 volts per microsecond

Frequency Response

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

Total Harmonic Distortion

< 0.2 % at full power
< 0.03 % at typical listening levels

IM Distortion

< 0.04 %

TIM

Unmeasureable

Dynamic Headroom

> 1.5 dB

Interchannel Crosstalk

> 78 dB at 1 kHz
> 63 dB at 20 kHz

Input Impedance

Unbalanced: 47k Ω
Balanced: 94k Ω

Input Sensitivity for 28.28 V Output into 8 Ω

Unbalanced: 1 V
Balanced: 1 V per leg

S/N Ratio

> 112 dB, input shorted, IHF A-weighted
> 102 dB, input shorted, unweighted

Damping Factor

> 1100 at 20 Hz

DC Trigger Requirements

+9 Vdc to +12 Vdc, 2 mA

Audio Trigger Requirements

50 mV AC - 250 mV AC

Dimensions

Width: 171⁄2" (445 mm)
Panel height: 7" (178 mm)
Height with feet: 7-5⁄8" (194 mm)
Depth: 19-1/8" (485 mm)

Power Requirement

Standby: 1 Watt
Full Power into 4Ω: 1800 Watts

Net Weight

65 lb. (29.5 kg)

Shipping Weight

79 lb. (35.9 kg)

Product Warranty

Parts & Labor

5 Years

2 Years for Moving Parts, Remote Controls, Lasers, Front Panel Displays and Video Screens

Parasound Warranty Information

Product Manual

	Parasound Halo A 31 Owner's Guide (PDF Format)

	2019 Parasound Halo Product Line Brochure (PDF Format)

"Recommended Component" 2020 - Stereophile

"Based on circuitry developed by John Curl for the highly praised Halo JC 1, the three-channel A 31 power amplifier is rated to deliver 250Wpc into 8 ohms or 400Wpc into 4 ohms. Like other Halo models, the A 31 is solidly built and has a clean, attractive, brushed-aluminum faceplate. On the rear panel are three groups of connectors/controls, one per channel, including balanced and unbalanced inputs and gain controls. Though it lacked some upper-bass richness, the A 31 had a 'clean, luminous' overall sound, with a sophisticated, detailed treble; rich, clean midrange; and firm, extended bass, said KR, adding that 'the sound is full, balanced and detailed and packs a wallop.'"

- Stereophile magazine, Vol.35 No.9

"The Halo A 31 has a clear, detailed sound that belies its price, combined with just a touch of warmth. This blend of qualities made it a joy to listen to. Add to that its prodigious power output and rock-solid build quality, and I can assure you: It’s the real deal."

"It’s a fantastic-sounding amp with power to spare. I consider the Halo A 31 to be one of today’s best values -- if not the best value -- in a power amplifier."

- Roger Kanno, SoundStage! Access, April 15, 2015

"The Halo A 31 is able to drive any speaker you are going to throw at it and not complain, as well as being impeccably built and beautiful in appearance."

"In fact, it performed so well I let Parasound know I'll be paying for it and keeping it as my reference amp going forward."

- Chris Heinonen, Secrets of Home Theater and High Fidelity, December 5, 2012