"I expected the A51 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
"Harmonic Rightness"
Barry Willis praises the Parasound A51 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 Halo A51 power 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 A51 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 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.
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 5-way speaker terminals, gold-plated RCA input jacks, and a rear-panel ground lift switch.
Interchannel crosstalk: >78 dB at 1 kHz, >63 dB at 20 kHz
Input impedance: unbalanced 47 K ohm, balanced 94 K ohm
Input sensitivity (for 28.28 V output into 8 ohm): unbalanced 1 V, balanced 1 V per leg
Slew rate: >130 volts per microsecond
Damping factor: >1100 at 20 Hz
DC trigger requirements: +9 VDC to +12 VDC, 2 mA
Audio trigger requirements: 50 mV AC - 250 mV AC
Power consumption: standby, 25 watts; full power into 4 ohms, 3000 watts
Weight: 77 lbs.
Shipping weight: 92 lb.
Dimensions: 17.5" wide, 20" deep, 7" high (7.625" with feet)
Manufacturer's limited warranty: 5 years parts, 5 years labor
"I expected the A51 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."
"Parasound's Halo A 51 is all the amp anyone could need. I can't imagine any audiophile -- 2-channel traditionalist or multichannel adventurer -- being unhappy with the A51."
- Barry Willis, Stereophile Guide to Home Theater, March/April, 2004
"As with the [Parasound] C2, I expected the A51 to sound good - with its John Curl design pedigree and close kinship to Curl's esteemed JC-1, I could expect no less. What I wasn't prepared for was how good the A51 sounded right out of the box. For the first two days it was in the system, I plowed through my CD collection, eagerly hunting out old favorites just to enjoy this amp's pure musicality."
"The A51 got very close to the Red Rose [Model II Silver Signature tube amp] in terms of absolute harmonic rightness - you know it when you hear it - and trounced by homemade amp in the departments of dynamic headroom and bass impact. 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."
"If that 2-channel test drive had me thinking about buying the A51, the multichannel experience made me want to slap down my Visa card… 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 A51 and C2 form an unbeatable combination - one that I intend to enjoy for a very long time. They exemplify elegance, ease of use, near-universal compatibility, and what appears to be universal reliability - backed by 10-year parts and 5-year labor warranties. Both get my highest recommendation."
- Barry Willis, Stereophile Guide to Home Theater, October 2003
"I found that this amp was able to extract the bass in even heavily compressed recordings, and helped balance the bright, smeared compressed artifacts sometimes found in the top end."
"As you can probably tell, I have been very impressed by the Halo products. ...Overall, this is a class-leading pair, and I do not say this lightly. The C2 package with it's sonic performance, automatic calibration, complete feature set, excellent remote, programmability, beautiful aesthetics, and hardware and software upgradeability is quite possibly the most complete processor package in the $4,000 area ...and rightly takes its place at the head of the pack."
"The A51 [amplifier] so thoroughly bettered the performance of my Classe' amp with the tough-to-drive KEF speakers that I cannot image going back to it."
"Parasound has totally hit the proverbial home run with the Halo C2 and A51 and I very strongly recommend them."
Rating: 98 out of 100."
- Manoj Motwani, M.D. DVD Etc. May 2003.
Audio Advisor Insight - Parasound High Value to Price Ratio
Audio Advisor Insight - Parasound in Hollywood
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good lookin piece,but rate it 4 out of 5 because of the the noise from the torroidal after it has been playin for a while
- Randy S, PA
Fantastic Sound and Excellent Product Quality
Unit sounded fabulous right out of the box. Parasound manufactures very high quality products. I would recommend this amplifier to any serious audiophile. The unit produces very crip mids and highs and very punchy, tight bass. You will love the A51!
