Parasound Halo A-21 Silver Faceplate

Editors' Choice Award Winner 2013 - The Absolute Sound Magazine

"Best Solid-State Amplifier" 2008/2009 - The Absolute Sound Magazine

250-Watt THX Ultra II Amp Hits a 'Home Run'

Parasound's Halo A21 two-channel power amplifier has the brute force you need for ultra-realistic musical reproduction and hair-raising movie soundtracks. Its raw power is matched by elegant circuit design from audio guru John Curl in collaboration with CTC Builders. 

"Highly Suitable for Driving Anything"

The Absolute Sound magazine rated the Halo A21 as the "Best Solid-State Amplifier" in the Winter 08 / Spring 09 issue, praising it as "highly suitable for driving anything from power-hungry planars like Maggies to low-sensitivity acoustic suspension cones."

The A21 is the two-channel version of Parasound's benchmark A51 five-channel amp, which the May 2003 issue of DVD Etc. magazine said hit the "proverbial home run." Matched JFET inputs, MOSFET drivers, and high-current bipolar outputs contribute to its exceptional performance. 

"Close Enough to the Very Best"

The Absolute Sound magazine awarded the Halo A21 its "Editors' Choice" recommendation for 2012. "Though not the last word in solid-state amplification, the A21 comes close enough to the very best, at such an affordable price…"

"Its luxurious appearance is more than skin deep. Parasound’s A21 dispensed truly sumptuous sound," notes England's Hi-Fi News magazine for November 2011. "Demonstrating the control and grip of the Bryston and Anthem but with the velvety midband richness of the ATC, the Parasound’s ability to resolve detail, while remaining composed and easy on the ear, proved the equal of my ‘reference’ Levinson amplifier." 

Balanced Inputs and Discrete Circuits

The A21 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 1.2 kVA encapsulated toroidal power transformer with independent secondary windings for each channel and 100,000 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 16 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 A21 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 five-way speaker terminals, gold-plated RCA input jacks, and a rear-panel ground lift switch.