Parasound Halo A21+ Two Channel Amplifier
The outgoing Parasound Halo A21 is the latest two channel power amplifier in the HALO series to get updated.
The new variant A21+ now has been developed with enhancements (both cosmetic and more fundamentally - internally) by the dedicated team at Parasound, to ensure that where necessary the natural development of benefits can be added and evolved.
The original award winning A21 power amplifier had been in the Parasound lineup unchanged for over ten years - which just shows you how popular and highly regarded they were!
Richard Schram, John Curl and the Parasound team's continuous development of their exemplary product line, naturally led them to learn from the new HINT 6 and also most prominently - the stunning new JC5.
In order to upgrade the A21 suitably to partner with the new and improved P6 Pre-amplifier (arguably the A21+'s primary fellow in stereo audio partnership), they have clearly outlined below some of the key enhancements and new features of the A21+
New Features (Changes from the original A21):
Power up from 250 → 300 Watts (8Ω)
Power up from 400 → 500 Watts (4Ω)
Power up from 750 → 1000 Watts (bridged)
Improved Filter capacitance: 88,000 uF → 108,000 uF
Improvved signal to noise ratio: S/N: 112dB → 115 dB
Exceptional low level distortion at higher levels: THD (at full power): 0.2% → 0.1%
Improved Crosstalk performance (20kHz): 63dB → 70dB
Enlarged Transformer size: 1.2 kVA → 1.3 kVA
Increased overall 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
Parasound’s new Halo A 21+ Amplifier with these latest embellishments is now arguably a future modern classic, with it's high current Class A/AB amplification, smooth sounding MOSFET drivers, and balanced XLR inputs, this mighty amp will make any speaker sound better than ever before.
The new A21+ two channel amplifier now boasts 300 watts of power per channel into an 8 ohm load, and even 500 watts per channel into a 4 ohm load. It can of course be used effectively as a 'mono-block' in bridged mode as well meaning that you can get up to a very dexterous 750-1000 watts into an 8ohm load for those of you requiring huge power into larger more challenging loads or larger spaces.
As you would expect the build quality and components used in the A21+ are like all of Parasound's range - are very high quality. Internally the new A21+ has upgraded internal gold on gold audio connections (cleaner signal path and more reliable.), a new larger main power transformer (10-15% larger), tweaked input circuits for improved crosstalk specs and in conjunction with the larger transformer - an improved power supply for lower distortion at full power. Even the audio trigger circuit has been updated for better control and sensitivity...
Externally in terms of upgrades on the visuals - the revised A21+ now has the slim metal end caps (replacing the wider plastic end caps), added gold metallic accent stripe along end cap, an engraved metal PARASOUND badge replaces the red P and gold feet now adorn the black units. In addition, the revised rear panel layout and features upgraded speaker terminals (A21+ gets the same new JC5 terminals.), a new jack/terminal layout with more space and more clear text/labels and the 2.5mm trigger jacks replaced with more 'standardised' 3.5mm jacks.
These upgrades are 'real-world' updates, not just an attempt to 'rebadge' the A21 - these are small but plentiful improvements that when combined together with the deftness and dedication Parasound are famous for....make a BIG difference.
As an the amplifier, with these new enhancements it can be sublimely subtle when required, and unflinchingly 'brutal' (in a terribly good way!) when raw power is needed. Remember - again the A21+ has the same high bias class A/AB operation of all John Curl's classics, and also has the benefit of the directly coupled design which means that there are no capacitors or inductors in signal path, which gives the utmost accuracy for the amplifier to work with. This balance of clarity and 'clout' means that it has real dynamic headroom for the best depth of field, aural texture and also finesse.
The A21+ can be used to stunning effect with the Parasound range of pre-amplifiers such as the JC2 BP, JC3+, the new improved P6 or the larger and flexible P7. So the A21+ is a real all rounder for want of a better phrase, but don't let this deftness fool you in any way shape or form.
The Parasound Halo A21+ is available in black and silver finishes - please specify on order.
Parasound Halo A21+ Two Channel Amplifier Features & Benefits:
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
Parasound Halo A21+ Two Channel Amplifier Specifications:
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
NOTE: Bridged 4 Ω operation is not recommended
0.1% THD, RMS continuous power, full audio band (20 Hz - 20 kHz)
60 amps peak, per channel
> 130 volts per microsecond
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
< 0.04 %
> 80 dB at 1 kHz
> 70 dB at 20 kHz
Unbalanced: 33 kΩ
Balanced: 66 kΩ,(33 kΩ per leg)
Input Sensitivity for 28.28 V Output into 8 Ω:
Unbalanced: 1 V
Balanced: 1 V per leg
> 115 dB, input shorted, IHF A-weighted
> 110 dB, input shorted, unweighted
> 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)
Width: 448 mm
Height without feet: 181 mm
Height with feet: 197 mm
Depth: 508 mm
Depth with cables: 546 mm
Standby: 1 Watt
Idle (no music playing): 160 Watts
Typical Listening levels: 300 Watts
Maximum: 1400 Watts
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