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Description

The Halo A 21+ power amplifier is a pinnacle of power and fidelity

The 21+ has two channels providing 250 watts per channel into 8 Ω, it delivers breathtaking audio performance. The high bias Class A/AB operation ensures accurate and detailed sound reproduction, while the stable operation into 2 Ω loads allows for versatility in speaker configurations. The direct-coupled design, free from capacitors in the signal path, preserves signal integrity and enhances transparency. With balanced XLR and unbalanced RCA inputs and A/B speaker terminals, it offers flexibility and compatibility. Experience pure power and fidelity with the Halo A 21+ power amplifier.

Changes from the original A 21→A 21+

  • 250 → 300 Watts (8Ω)
  • 400 → 500 Watts (4Ω)
  • 750 → 1000 Watts (bridged)
  • Filter cap: 88,000 uF → 108,000 uF
  • S/N: 112dB → 115 dB
  • THD (at full power): 0.2% → 0.1%
  • Crosstalk (20kHz): 63dB → 70dB
  • Transformer size: 1.2 kVA → 1.3 kVA
  • Weight: 60 LB → 71 LB
  • Refined Halo cosmetic with aluminum end caps & gold highlights
  • Updated rear panel with heavy duty speaker terminals from JC 5
  • Upgraded internal gold on gold audio connections
  • Updated auto turn on circuit

Features

  • 300 watts x 2 @ 8 Ω RMS, both channels driven
  • 500 watts x 2 @ 4 Ω RMS, both channels driven
  • 1000 watts x 1 @ 8 Ω, in bridged mode
  • Circuitry designed by legendary John Curl
  • High bias Class A/AB operation
  • 60 amperes peak current per channel
  • Stable with speaker impedance dips to 1.5 Ω
  • Balanced inputs with discrete circuits
  • CHK Infinium, custom 5-way speaker binding posts
  • Gold-plated RCA input & loop output jacks
  • Direct-coupled signal path, no capacitors or inductors
  • DC Servo and relay protection circuits
  • AC turn-on inrush surge protection with relay bypass
  • JFET input stage, MOSFET driver stage
  • 16 beta-matched 15 ampere, 60 MHz bipolar output transistors
  • 1.3 kVA shielded toroid transformer w/ independent windings for each channel
  • Independent power supplies for input stage, driver stage and output stage
  • 108,000 µF filter capacitors for output stages
  • Full power is rated all the way down to 5Hz for unrestricted low-end bass
  • Harris hyper-fast soft-recovery bridge diode rectifiers
  • Automatic turn-on by 12 V trigger or audio sensing
  • 4 rack space chassis with rear carry handles
  • Rack mount hardware is included
  • Available in silver or black

Specifications

Power Output – Stereo Mode (0.1% THD)
300 watts x 2, 8 Ω both channels driven
500 watts x 2, 4 Ω both channels driven

Power Output – Bridged Mode (0.1% THD)
1000 watts x 1, 8 Ω
Bridged 4 Ω operation is not recommended

Power measurement are at 120 VAC:
0.1% THD, RMS continuous power,
full audio band (20 Hz - 20 kHz)

Current Capacity
60 amps peak, per channel

Slew Rate
> 130 volts per microsecond

Frequency Response
5 Hz - 100 kHz, +0/-3 dB
20 Hz - 20 kHz, +0/-0.25 dB

Total Harmonic Distortion (THD)
< 0.1 % at full power
< 0.03 % at typical listening levels

IM Distortion
< 0.04 %

TIM
Unmeasurable

Inter-channel Crosstalk
> 80 dB at 1 kHz
> 70 dB at 20 kHz

Input Impedance
Unbalanced: 33 kΩ
Balanced: 66 kΩ,(33 kΩ per leg)

Total Gain
29 dB

Input Sensitivity for 28.28 V Output into 8 Ω
Unbalanced: 1 V
Balanced: 1 V per leg

S/N Ratio
> 115 dB, input shorted, IHF A-weighted
> 110 dB, input shorted, unweighted

Damping Factor
> 1100 at 20 Hz

DC Trigger Requirements
+9 Vdc to +12 Vdc, 5 mA

Audio Trigger Requirements
2 mV - 10 mV

XLR Pin Identification
1 = Ground (Shield)
2 = Positive
3 = Negative (Return)

Dimensions
Width: 17-5/8" (448 mm)
Height without feet: 7-1/8" (181 mm)
Height with feet: 7-3/4" " (197 mm)
Depth: 20" (508 mm)
Depth with cables: 21-1/2" (546 mm)

Net Weight
71 lb. (32.2 kg)

Shipping Weight
88 lb. (39.9 kg)

Power Requirement
Standby: 1 Watt
Idle (no music playing): 160 Watts
Typical Listening levels: 300 Watts
Maximum: 1400 Watts

Reviews

Stereophile March 2020
"The new Parasound A 21+ was impossible to fault... remarkably powerful, transparent and quiet. Anyone in the market for a stereo power amp would be well advised to consider the Parasound A 21+, especially those who believe that they must spend more."

Home Theater Review Feb 2020
"With its high-quality chassis, thoughtful circuit design, and excellent sound quality, the A 21+ offers an impressive value proposition. Those shopping for a stereo amplifier in this price range should give the A 21+ serious consideration."

Positive Feedback January 2019
"The A 21+ represents a new unparalleled value in amplifier performance. Details like soundstage depth, focus, and texture is where the A 21+ puts real distance from the A 21. The A 21+ is exceptional and provided an awe-striking feel."

Support and Downloads

Download Manual

HALO A21+ Power Amp - SILVER

Regular price $3,599.00

The Halo A 21+ power amplifier is a pinnacle of power and fidelity

The 21+ has two channels providing 250 watts per channel into 8 Ω, it delivers breathtaking audio performance. The high bias Class A/AB operation ensures accurate and detailed sound reproduction, while the stable operation into 2 Ω loads allows for versatility in speaker configurations. The direct-coupled design, free from capacitors in the signal path, preserves signal integrity and enhances transparency. With balanced XLR and unbalanced RCA inputs and A/B speaker terminals, it offers flexibility and compatibility. Experience pure power and fidelity with the Halo A 21+ power amplifier.

Changes from the original A 21→A 21+

  • 250 → 300 Watts (8Ω)
  • 400 → 500 Watts (4Ω)
  • 750 → 1000 Watts (bridged)
  • Filter cap: 88,000 uF → 108,000 uF
  • S/N: 112dB → 115 dB
  • THD (at full power): 0.2% → 0.1%
  • Crosstalk (20kHz): 63dB → 70dB
  • Transformer size: 1.2 kVA → 1.3 kVA
  • Weight: 60 LB → 71 LB
  • Refined Halo cosmetic with aluminum end caps & gold highlights
  • Updated rear panel with heavy duty speaker terminals from JC 5
  • Upgraded internal gold on gold audio connections
  • Updated auto turn on circuit

Features

  • 300 watts x 2 @ 8 Ω RMS, both channels driven
  • 500 watts x 2 @ 4 Ω RMS, both channels driven
  • 1000 watts x 1 @ 8 Ω, in bridged mode
  • Circuitry designed by legendary John Curl
  • High bias Class A/AB operation
  • 60 amperes peak current per channel
  • Stable with speaker impedance dips to 1.5 Ω
  • Balanced inputs with discrete circuits
  • CHK Infinium, custom 5-way speaker binding posts
  • Gold-plated RCA input & loop output jacks
  • Direct-coupled signal path, no capacitors or inductors
  • DC Servo and relay protection circuits
  • AC turn-on inrush surge protection with relay bypass
  • JFET input stage, MOSFET driver stage
  • 16 beta-matched 15 ampere, 60 MHz bipolar output transistors
  • 1.3 kVA shielded toroid transformer w/ independent windings for each channel
  • Independent power supplies for input stage, driver stage and output stage
  • 108,000 µF filter capacitors for output stages
  • Full power is rated all the way down to 5Hz for unrestricted low-end bass
  • Harris hyper-fast soft-recovery bridge diode rectifiers
  • Automatic turn-on by 12 V trigger or audio sensing
  • 4 rack space chassis with rear carry handles
  • Rack mount hardware is included
  • Available in silver or black

Specifications

Power Output – Stereo Mode (0.1% THD)
300 watts x 2, 8 Ω both channels driven
500 watts x 2, 4 Ω both channels driven

Power Output – Bridged Mode (0.1% THD)
1000 watts x 1, 8 Ω
Bridged 4 Ω operation is not recommended

Power measurement are at 120 VAC:
0.1% THD, RMS continuous power,
full audio band (20 Hz - 20 kHz)

Current Capacity
60 amps peak, per channel

Slew Rate
> 130 volts per microsecond

Frequency Response
5 Hz - 100 kHz, +0/-3 dB
20 Hz - 20 kHz, +0/-0.25 dB

Total Harmonic Distortion (THD)
< 0.1 % at full power
< 0.03 % at typical listening levels

IM Distortion
< 0.04 %

TIM
Unmeasurable

Inter-channel Crosstalk
> 80 dB at 1 kHz
> 70 dB at 20 kHz

Input Impedance
Unbalanced: 33 kΩ
Balanced: 66 kΩ,(33 kΩ per leg)

Total Gain
29 dB

Input Sensitivity for 28.28 V Output into 8 Ω
Unbalanced: 1 V
Balanced: 1 V per leg

S/N Ratio
> 115 dB, input shorted, IHF A-weighted
> 110 dB, input shorted, unweighted

Damping Factor
> 1100 at 20 Hz

DC Trigger Requirements
+9 Vdc to +12 Vdc, 5 mA

Audio Trigger Requirements
2 mV - 10 mV

XLR Pin Identification
1 = Ground (Shield)
2 = Positive
3 = Negative (Return)

Dimensions
Width: 17-5/8" (448 mm)
Height without feet: 7-1/8" (181 mm)
Height with feet: 7-3/4" " (197 mm)
Depth: 20" (508 mm)
Depth with cables: 21-1/2" (546 mm)

Net Weight
71 lb. (32.2 kg)

Shipping Weight
88 lb. (39.9 kg)

Power Requirement
Standby: 1 Watt
Idle (no music playing): 160 Watts
Typical Listening levels: 300 Watts
Maximum: 1400 Watts

Reviews

Stereophile March 2020
"The new Parasound A 21+ was impossible to fault... remarkably powerful, transparent and quiet. Anyone in the market for a stereo power amp would be well advised to consider the Parasound A 21+, especially those who believe that they must spend more."

Home Theater Review Feb 2020
"With its high-quality chassis, thoughtful circuit design, and excellent sound quality, the A 21+ offers an impressive value proposition. Those shopping for a stereo amplifier in this price range should give the A 21+ serious consideration."

Positive Feedback January 2019
"The A 21+ represents a new unparalleled value in amplifier performance. Details like soundstage depth, focus, and texture is where the A 21+ puts real distance from the A 21. The A 21+ is exceptional and provided an awe-striking feel."

Support and Downloads

Download Manual

HALO A21+ Power Amp - SILVER
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