Parasound Halo A23+ Stereo Power Amplifier

A 23+ Stereo Power Amplifier

Halo

This Halo Shines More Beautifully Than Ever

Parasound already brings listeners heavenly sound, but its halo now shines more beautifully than ever with its brand new version of the Halo A 23 two-channel power amplifier. Meet the Halo A 23+ and enjoy performance upgrades for cleaner, ultra-low distortion sound, revised front panel cosmetics, and a revised rear panel layout offering enhanced features, too.

"Together, the Parasound P 6 and A 23+ are dynamite," raves Roy Ervin Solstad, Stereo+ (Norway), January 2019. "Pure sonic magic with brilliant dynamics, delicious midrange and impressive resolution. To get such good sound for the price of this duo seems almost unnatural. One incredibly appealing preamp-amplifier package from Parasound."

Impressive Performance Upgrades

The performance upgrades are impressive, beginning with a big 25% to 30% increase in output power compared to the previous model. The A 23+ delivers 160 watts-per-channel at 8 ohms compared to 125 watts-per-channel for the A 23, 240 watts-per-channel compared to 225 watts-per-channel at 4 ohms, and 500 watts in bridged mono mode compared to 400 watts with the A 23.

The performance of a power amplifier is highly dependent on the quality of its power supply, and Parasound went the extra mile with the A 23+, which boasts a 10% to 15% larger main power transformer compared to the previous model A 23. Transformer size has been increased from 1.0 to 1.1kVA, and the filter capacitance increases 20-30% from 40,000 uF for the A 23 to 54,400 uF for the new A 23+. You'll hear the advantages of these upgrades as the A23+ presents lower distortion at full power.

Other performance upgrades include tweaked input circuits for improved crosstalk specs (70 dB at 20 kHz compared to 63 dB) and upgraded internal gold on gold audio connections, resulting in a cleaner signal path that's also more reliable.

Rear Panel Layout and Features Upgrades

The rear panel of the A 23+ has been revised in terms of layout and new features. It boasts upgraded speaker terminals, using identical terminals to the HINT 6 integrated amp, a new jack/terminal layout with more space and more clear text/labels, and a master "Vacation" AC switch. The 2.5mm trigger jacks of the A 23 have been replaced with 3.5mm jacks, and the audio trigger circuit has been updated for better low signal reliability.

Revised Halo Front Panel Cosmetics

The Halo series has always been known for its elegant aesthetics, and the look is even better than before. New front panel cosmetics include slim metal end caps replacing wider plastic end caps, an added gold metallic accent stripe along the end cap, gold feet now on black units, and an engraved metal "Parasound" badge replacing the red "P."

Advanced John Curl-Designed Circuitry

The circuitry of the A 23 was engineered by legendary audio designer John Curl. Its direct-coupled topology uses no capacitors or inductors in the signal path for pure, uncolored sound. Balanced inputs with discrete circuits and XLR connectors yield dead quiet operation. The complementary JFET input stage and MOSFET drive stage incorporates 12 beta-matched 15 amp, 60 MHz bipolar output transistors for pristine sound. The high-bias "Class A"/"Class AB" operation blends best sound with highest efficiency performance.

The A 23's custom-made, high-current power supply is specially designed for exceptionally quiet operation along with ample power for climactic music passages. The 1.1KVA encapsulated toroidal power transformer uses independent secondary windings for each channel along with a 54,400 µF power supply filter capacitance. DC servo and relay protection circuits keep operation safe and reliable. And Parasound backs the A 23+'s reliability with an impressive warranty.

No Need for a Remote

The front panel of the A 23+ looks great even when the unit is turned off. When you switch the Halo on, LEDs display AC-present, channel, and high temperature status. Adjustable signal sensing can be set to automatically power up the A23 when it receives a signal from your preamp or other compatible component (or when it receives a 12-volt trigger command), eliminating the need for yet another wireless remote!

'Instant Warm-up' Feature

Like all the other amps in the Halo product series, the A 23+ 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. 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.

Changes from the original A 23→A 23+

• 125 → 160 Watts (8Ω)
• 225 → 240 Watts (4Ω)
• 400 → 500 Watts (bridged)
• Filter cap: 40,000 uF →54,400 uF
• Crosstalk (20kHz): 63dB → 70dB
• Transformer size: 1.0 kVA → 1.1 kVA
• Refined Halo cosmetic with aluminum end caps & gold highlights
• Updated rear panel with heavy duty speaker terminals from HINT 6
• Upgraded internal gold on gold audio connections
• Updated auto turn on circuit

All Features

• 160 watts x 2 @ 8 Ω RMS, both channels driven
• 240 watts x 2 @ 4 Ω RMS, both channels driven
• 500 watts x 1 @ 8 Ω, in bridged mode
• Circuitry designed by legendary John Curl
• High bias Class A/AB operation
• 45 amperes peak current per channel
• Stable with speaker impedance dips below 2 Ω
• Balanced inputs with discrete circuits
• Heavy-duty 24k gold-plated 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
• 12 beta-matched 15 ampere, 60 MHz bipolar output transistors
• 1.1 kVA shielded toroid transformer w/ independent windings for each channel
• Independent power supplies for input stage, driver stage and output stage
• 54,400 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
• 2 rack space chassis with rear carry handles
• Rack mount hardware available separately
• Available in black

Power Output – Stereo Mode (0.06% THD)
160 watts x 2, 8 Ω both channels driven
240 watts x 2, 4 Ω both channels driven

Power Output – Stereo Mode (0.9% THD)
210 watts x 2, 8 Ω both channels driven
300 watts x 2, 4 Ω both channels driven

Power Output – Bridged Mode (0.06% THD)
500 watts x 1, 8 Ω
Bridged 4 Ω operation is not recommended

Power Output – Bridged Mode (0.9% THD)
600 watts x 1, 8 Ω
Bridged 4 Ω operation is not recommended 

*All Power measurement are at 120 VAC,
RMS continuous power, full audio band (20 Hz - 20 kHz)

Current Capacity
45 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)
< 0.06 % at full power
< 0.03 % at typical listening levels

IM Distortion
< 0.04 %

TIM
Unmeasurable

Inter-channel Crosstalk
> 85 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 Out (8 Ω Load)
Unbalanced: 1 V
Balanced: 1 V per leg

S/N Ratio
> 112 dB, input shorted, IHF A-weighted
> 107 dB, input shorted, unweighted

Damping Factor
> 800 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: 17-1/4" (437 mm)
Depth: 15"-1/4" (388 mm)
Depth, with cables 17" (432 mm)
Height, with feet: 4-1/8" (105 mm)
Height, without feet: 3-1/2" (89 mm), 2U

Net Weight
27 lb. (12.2 kg)

Shipping Weight
34 lb. (14.4 kg)

Power Requirement
Standby: <1 Watt 
Idle (no music playing): 75 Watts 
Typical Listening levels: 125 Watts
Maximum: 800 Watts
110-125 VAC 60 Hz or 220-250 VAC 50 Hz
AC mains voltage is set on rear panel