Parasound Halo A 31 Three Channel Power Amplifier - Black

Parasound Gave the Front Three Channels Their Own Amplifier

A home theater asks the most of its front three speakers. Dialogue sits in the center. Most of the score and the loudest effects land left and right. The Halo A 31 gives each of those channels 250 watts into 8 ohms, with all three driven at once.

Drop to 4 ohms and each channel makes 400 watts. Every channel accepts an XLR or an RCA input, and a rear switch chooses between them. The chassis fills 4U of rack space, weighs 65 pounds, and a rack adapter comes in the box.

Why Three Channels Instead of Five

Surround speakers seldom work as hard as a center channel does. Paying for amplification on the front three alone puts the money where the effort goes, and leaves your receiver or a second amplifier to look after the rest of the room.

Sixty Amps a Channel, and Where They Come From

Each channel draws on a 1.5 kVA encapsulated toroidal transformer with its own secondary winding, backed by 98,400µF of filter capacitance. Peak current capacity is 60 amperes per channel. Eight beta-matched bipolar output transistors carry each channel.

John Curl designed the circuit. JFETs handle the input stage and MOSFETs the drivers. No capacitor or inductor sits between input and output, and Parasound quotes a slew rate above 130 volts per microsecond.

The Numbers Behind the Claim

Total harmonic distortion stays under 0.2 percent at full power, and under 0.03 percent at the levels most people listen at. Intermodulation distortion measures under 0.04 percent. Signal-to-noise ratio beats 112 dB A-weighted, and channel separation beats 78 dB at 1 kHz.

Damping factor is better than 1100 at 20 Hz. Frequency response runs from 5 Hz to 100 kHz within 3 dB at one watt. The A 31 carries THX Ultra2 certification, and a rear gain control gives up to 6 dB of adjustment.

What Reviewers Are Saying

Chris Heinonen, writing in Secrets of Home Theater and High Fidelity on December 5, 2012: "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."

Roger Kanno in SoundStage! Access, April 15, 2015: "its midrange clarity and ability to vividly float voices between the speakers at exactly the right depth -- not too up-front or recessed -- rivaled that of much more expensive amps."

Who Is This Three-Channel Amplifier Best For?

• Your front three speakers do most of the work — 250 watts reach each of them at the same moment, so dialogue stays clear and effects keep their weight when a soundtrack turns loud
• Your speakers dip toward 4 ohms — each channel doubles to 400 watts there, with 60 amperes of peak current behind it, so a difficult load does not flatten what you hear
• You want certified headroom — the A 31 is THX Ultra2 certified, and up to 6 dB of gain adjustment lets you level match it against whatever drives your surround channels
• Your gear lives in a rack — a 4U chassis with carry handles and an included rack adapter goes in cleanly, and a 12V trigger wakes it along with everything else
• You will add amplification for the surrounds — this covers three channels, so the rest of a 5.1 or 7.1 room still needs power; run it beside your receiver’s own channels, or add one of our multi-channel amplifiers, and the front three keep the best of it

How Does It Connect to Your System?

Feed three preamp outputs from your processor or receiver into the amplifier. Each channel takes either an XLR or an RCA cable, and a small switch beside the jacks picks which one is live. Then run speaker cable to the five-way binding posts.

For power, choose the front switch, a 12V trigger, or signal sensing with an adjustable threshold. Two trigger cables come in the box. Set it once and the amplifier follows the rest of the system.

Pairs Well With

A power amplifier needs a few things around it. These are the categories most A 31 owners shop next.

• Home theater receivers — the preamp outputs that feed all three channels
• Interconnect cables — three balanced XLR or unbalanced RCA runs from the processor
• Speaker cables — heavier wire for the binding posts to grip
• Power conditioners — a clean feed for an amplifier that can draw 1800 watts

Frequently Asked Questions

Do I need a receiver or processor with this amplifier?

Yes. The A 31 supplies power and nothing else. Feed it from the preamp outputs of an AV receiver or a surround processor.

How much power does it make with all three channels driven?

250 watts per channel into 8 ohms, and 400 watts per channel into 4 ohms. Parasound quotes both continuously, from 20 Hz to 20 kHz.

Can I choose between the XLR and RCA inputs?

Each channel carries both, with a switch beside the jacks to select one. Set every channel to match the source feeding it.

What comes in the box?

An AC power cord and two trigger cables. One has 3.5 mm mini plugs at both ends, and the other has a 2.5 mm plug and a 3.5 mm plug.

Will it fit an equipment rack?

It will. The chassis is 4U with carry handles, and Parasound includes a rack adapter. Panel height is 7 inches, or 178 mm.

How does it turn on?

Three ways. Use the front switch, send a 12V trigger of +9 to +12 volts, or let it sense audio and start on its own, with a threshold you set.

See It in Action

Dreamedia Home Theater unboxes the A 31:

That Home Theater Dude spends eleven minutes unboxing one and setting it up:

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