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Parasound Halo A51 Multi Channel Amplifier
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Parasound Halo A51 Multi Channel Amplifier

£4,165.83 Exc. VAT |  


Parasound Halo A51 Multi Channel Amplifier

The Parasound HALO A51 multichannel amplifier is a power amplifier with huge presence and poise - befitting of it's legendary designer John Curl.

The HALO A51 is a thoroughbred THX Ultra2 certified, high bias Class A/AB amplifier that gives you the optimal amount of performance that only most really high end systems achieve, again nailing Parasound's colours to the mast when it comes to that getting the maximum 'bang for your buck'.

The A51 is perfect for any higher end multi-channel application, and will drive the most demanding of loads within a system - so it is perfect not only for very good quality custom installation in-wall systems, but obviously is equally sure footed with large floor-standers as well. The root of this adaptability is primarily it's 2.2 kVA encapsulated toroid power transformer with independent secondary windings for each channel, plus the A51's high bias class A/AB operation working in tandem with it's directly coupled design (there are no capacitors or inductors in signal path). 

These elementary features provide the structure on which the amplifier can give the real performance that other manufacturer's put on paper - but rarely deliver, meaning that the Halo A51 is the only choice for those really wanting visceral and dynamic performance. This power and dynamism is quantifiable as the A51 can output between 250watts to 400watts per channel - this is a real world measurement as this is whilst all channels are being driven (20 Hz - 20 kHz - 60 amperes peak per channel). This high power and high current output performance delivers very flexible dynamic 'headroom', which is why the amplifier can be sublimely subtle when required, and unflinchingly severe when raw power is needed.

As you would expect the build quality and components used in the A51 are pretty much second to none. The seriousness of the amplifier can be seen externally with the casework - as the A51's 4u chassis is solidly constructed to the best standards and also has rear mounted carry handles (rack mounting adapter included for custom installation applications) for moving it's impressive footprint to where you need it.

The A51 features both balanced and unbalanced inputs (RCA's are gold plated) with a designated ground lift switch, and these high quality inputs are matched with heavy-duty 24k gold-plated 5-way speaker terminals on the output stage. Befitting of it's high end custom installation pedigree the A51 also features auto turn on and a reliably solid 12v trigger for integration with processors, pre-amps or control systems.

We all appreciate that there are many amplifiers out there that provide enough power to blow doors off, but power and raw energy is one thing - but to couple this with musicality, subtlety and real dynamic range is not fact it can be extremely difficult to achieve, and this is where the A51 really separates the 'men from the boys' so to speak.

The Parasound Halo A51 is available in black and silver finishes - please specify on order.


  • 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

Continuous power output (all channels driven):

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

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


  • 110V - 120V


  • 171⁄2" (445 mm)

Panel height:

  • 7" (178 mm)

Height with feet:

  • 75⁄8" (194 mm)


  • 20" (508 mm)

Net weight:

  • 80 lb. (36.4 kg)

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