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Parasound A 31 Three-Channel Power Amplifier (Each)

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The Parasound A 31 Three-Cannel Power Amplifier 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.


  • 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


  • Continuous power output:
    250 watts RMS x 3, 20 Hz – 20 kHz, 8 Ω, all channels driven
    400 watts RMS x 3, 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)
  • 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
  • Dimensions:
    17-1/2″ w x 7-5/8″ h x 20″ d, 7″ h without feet
  • Net weight: 65 lb.
  • Shipping weight: 79 lb.


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.


“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.”


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.


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.


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.


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.




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