“I expected the Parasound Halo A 51 Amplifier to sound good. What I wasn’t prepared for was how good it sounded right out of the box. Its midrange was totally seductive, its soundstage and imaging capabilities in the same league as some of the best gear I’ve ever heard at any price.” — Barry Willis, Stereophile Guide to Home Theater, “Recommended Components,” March/April, 2004
Raw Power Meets Elegant Circuit Design
Barry Willis praises the Parasound Halo A51 amplifier for its “harmonic rightness” in Stereophile Guide to Home Theater for October 2003. “Its midrange was totally seductive, its soundstaging and imaging abilities in the same league as some of the best gear I’ve ever heard at any price… With music, the A51 radiated sweetness and light. With action films, it rained thunder and lightning. There aren’t many amplifiers that can so effortlessly cover both ends of the sonic spectrum.”
The Jan / Feb. 2004 Top Choice Awards issue of DVD ETC. magazine praises the Halo A51 multichannel amp and the Halo C2 surround sound processor for their “sonic performance, auto calibration, complete feature set, programmability and upgradeability.”
Uncompromising Audiophile Performance
Parasound’s five-channel Parasound Halo A51 amplifier combines raw power with elegant circuit design. Designed by legendary audio guru John Curl in collaboration with CTC Builders, 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. Matched JFET inputs, MOSFET drivers, and high-current bipolar outputs contribute to its exceptional performance.
Class A / AB Operation and Impressive Firepower
The Parasound Halo A51 amplifier 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 2.2 kVA encapsulated toroidal power transformer with independent secondary windings for each channel and 164,000 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 40 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 Parasound Halo A 51 Amplifier 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 of the Parasound Halo A51 amplifier include heavy-duty 24k gold-plated 5-way speaker terminals, gold-plated RCA input jacks, and a rear-panel ground lift switch.
Continuous power output:
250 watts RMS x 5, 20 Hz - 20 kHz, 8 , all channels driven
400 watts RMS x 5, 20 Hz - 20 kHz, 4 , all channels driven
60 amperes peak per channel
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 %
> 130 V/ second
> 1.5 dB
> 78 dB at 1 kHz;
> 63 dB at 20 kHz
1 V for 28.28 V, THX Reference Lev
47 k unbalanced; 94 k balanced
112 dB, input shorted, IHF A-weighted
> 1100 at 20 Hz
110V - 120V
17-1/4" w x 7-5/8" h x 20" d, 7" h without feet
Net weight: 80 lb.
- Continuous power output:
- 250 watts RMS x 5, 20 Hz - 20 kHz, 8 Ω, all channels driven
400 watts RMS x 5, 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 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
- Dimensions (WxHxD):
- 17-1/2" x 7-5/8" x 20"
- 80 lbs.