• 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
• 16 beta-matched 15 amp, 60 MHz bipolar output transistors
• 1.2 kVA encapsulated toroid power transformer with independent secondary windings for each channel
• 88,000 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, 12v trigger out
• 4u Chassis, carry handles, rack mounting adapter included

Continuous power output:
250 watts RMS x 2, 20 Hz - 20 kHz, 8 Ω, all channels driven
400 watts RMS x 2, 20 Hz - 20 kHz, 4 Ω, all channels driven
750 watts RMS x 1, 20 Hz - 20 kHz, 8 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:
> 80 dB at 1 kHz;
> 63 dB at 20 kHz

Input sensitivity:
1 V for 28.28 V, THX Reference Level

Input impedance:
33 k Ω unbalanced; 66 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: 60 lb.

Support and Downloads

A21 Manual

Stereo&Video (May, 2014)
"This amazing group of equipment best demonstrates the audio industry's present state of the art."

SoundReproduction.com, October 2005
"Out of the box the A 21 sounds wonderful. I sampled several Red Book CD's of different recording quality and musical genera's and quickly came to the realization that the A 21 was indeed a very special amplifier, and I could not wait to begin the serious evaluation after burn-in." - Shane Mattson

Audioholics, December 2004
Product of the Year Award 2004 - Two-Channel Power Amplifier
"For those who desire the power of a Mack truck with the finesse of a Mercedes Benz in a two-channel amplifier, look no further than Parasound." "With the assortment of unbalanced and balanced inputs, triggered output, and ground lift option no stones were left unturned with this well built, attractive design."

Audioholics, October 2004
"The A 21 and A 51 amplifiers are both loaded with usable features above and beyond most other amplifiers in today's market." "I cranked the volume way up and found myself free of that inhibiting audio alarm in my head that nags at me to turn it back down. Using the Parasound amp allowed my speakers to portray every aspect that I had come to expect without adding any noticeable sign of distortion or flaw." "The Parasound Halo A 21 and A 51 are top rate amplifiers at a great value. Parasound seems to have attended to every aspect of their design including the excellent build quality internally and externally matched with great looks." Overall Rating: 5/5 Stars - Ken Stein and Steve Dellasala

Luister (Netherlands), November 2003

Audiophile.no (Norway), July 2003