Parasound Halo A23+ 2-Channel Power Amp (Black)

Circuit Designed by John Curl

Parasound design consultant John Curl has been a legend among audiophiles and electronic engineers for decades. He pioneered measurements to correlate musical accuracy with the materials used in parts, worked with world-class touring companies, has designed highly coveted audio classics, including the original Mark Levinson JC-2, Denneson JC-80, Vendetta Phono Preamplifier, and CTC Blowtorch preamplifiers; master recorders for Wilson Audio and Mobile Fidelity; and the mixing consoles used in live concerts by The Grateful Dead and the Montreux Jazz Festival in Switzerland.

Carefully Selected Components

Every part within the A23+ is carefully chosen for its accuracy and reliability. Metal film resistors with 1% tolerance are selected for their precision and because their values don�t drift as they heat up during operation. Polypropylene and mica capacitors are used extensively for their superior linearity and low dielectric absorption. Semiconductors are selected for superior performance in their specific roles in the circuit. Gold has the best conductivity of any metal, so high-quality gold-plated input connectors and speaker terminals are used. The double-sided circuit boards are FR4 glass epoxy for long-term durability. The chassis is made of heavy gauge steel to safely house the internal circuitry. This attention to detail when selecting parts makes the difference between a very good amplifier and an outstanding amplifier.

Audio Circuit Path Topology

Parasound�s circuit topology is a hybrid of carefully chosen discrete transistors that result in superior performance at each stage. Parasound uses JFETs (Junction Field Effect Transistors) for the input stage, MOSFETs (Metal Oxide Field Effect Transistors) for the driver stage, and bipolar transistors for the output stage. Discrete transistors are more sonically accurate than integrated circuits commonly used by other brands.

Bridged Mode

Bridged operation configures the left and right channels to function as a single channel higher power amplifier to drive a single speaker. When an A23+ is in Bridged Mode it provides far greater power output than the sum of its left and right channels' power output. Please note that in bridged operation the minimum speaker impedance is 8 ohms. It is not recommended to use the A23+ with a 4-ohm speaker while set to bridged mode.

Bi-Amping Capability

Bi-amping is another option to increase power delivery per speaker. Similar to bridged-mono operation, bi-amping requires one A23+ amplifier per speaker. Bi-amping also requires speakers with separate LF (Low Frequency) and HF (High Frequency) input terminals with removable metal straps or wires. The left channel of the first A23+ will power the LF section of one speaker and this same A23+�s right channel will power the HF section of the same speaker. The second A23+ will connect the same way to the second speaker�s LF and HF inputs. When bi-amping, both A23+�s Bridged switches must be set to their Normal (Stereo) position.

Class-A/AB Operation

Pure Class-A operation provides the purest sound. However, an amplifier operating entirely in Class-A would be enormous, highly inefficient, and generate far too much heat. Class-AB combines the main advantages of Class-A with the efficiency of Class-B operation. It is a compromise that reduces the heat generated in pure Class-A operation and the higher order odd harmonic distortions created in Class-B. In Class-AB, the driver and output stages are always partially turned on, which provides a nominal amount of pure Class-A operation. At higher power levels, when the musical waveform swings from positive to negative and vice versa, each bank of transistors is allowed to rest momentarily. This resting, or quiescent time, makes it possible to deliver high amounts of power without overheating. It also makes it possible to use passive cooling and avoid fans, whose noise can be heard over the music. The A 23+ input and driver stages employ pure Class-A while its output stage operates with higher level of pure Class-A power than many amplifiers selling for twice or three times its price. The result is less fatiguing, more natural sound.

Additional Features

• Direct coupled input circuits, no capacitors, or inductors in signal path
• 12 beta-matched 15 ampere, 60 MHz bipolar output transistors
• 1.1 kVA shielded toroid transformer with independent windings for each channel
• 54,400 µF filter capacitors for output stages
• Employs advanced DC Servo and relay protection circuits to protect against current overload and interference
• Dual voltage AC input, switchable on rear panel
• Rack mountable with HRA 2 Rack Mount Kit (sold separately)
• RCA Loop Out for daisy chaining signal to multiple amplifiers
• Speaker terminals accept banana plugs, spade connectors, or bare wire up to 10AWG
• Power on manually, with audio signal, or with 12V trigger
• Adjustable audio trigger sensitivity for auto-on function
• 12V trigger throughput
• Power, active channel, and high-temperature LED indicators on front panel

Parasound A23+ Specs

Channels	2.0
Power Output per Channel	2-Channel Driven: 160 W at 8 Ohms / 0.06% THD (RMS) 240 W at 4 Ohms / 0.06% THD 210 W at 8 Ohms / 0.9% THD 300 W at 4 Ohms / 0.9% THD 1-Channel Driven: 500 W at 8 Ohms / 0.06% THD (Bridged) 600 W at 8 Ohms / 0.9% THD (Bridged)
Rear A/V Outputs	2x RCA Pre-Out
Speaker I/O	2x Gold-Plated 5-Way Binding Post Pairs
Wi-Fi	No
Bluetooth	No

Amplifier Type	Power Amplifier
Channels	2.0
Amplifier Class	Class-AB
Power Output per Channel	2-Channel Driven: 160 W at 8 Ohms / 0.06% THD (RMS) 240 W at 4 Ohms / 0.06% THD 210 W at 8 Ohms / 0.9% THD 300 W at 4 Ohms / 0.9% THD 1-Channel Driven: 500 W at 8 Ohms / 0.06% THD (Bridged) 600 W at 8 Ohms / 0.9% THD (Bridged)
Frequency Response	5 Hz to 100 Hz 0/-3 dB 20 Hz to 20 kHz +0/-0.25 dB
THD	< 0.06% (Full Power)
Speaker Impedance	4 to 8 Ohms
Tone Control	No
Damping Factor	> 800 (20 Hz to 20 kHz)

Auro 3D Support	No
Supported Sample Rates	No

Rear A/V Inputs	2x Mono XLR Balanced Line 2x RCA Unbalanced Line
Rear A/V Outputs	2x RCA Pre-Out
Front I/O	No
Other Rear I/O	1x 1/8" / 3.5 mm (12 V Trigger) Input 1x 1/8" / 3.5 mm (12 V Trigger) Output
Speaker I/O	2x Gold-Plated 5-Way Binding Post Pairs
Media Card Slot	No
A/B Speaker Selection	No
Bi-Amp Capability	No
Input Impedance	RCA: 33 Kilohms XLR: 66 Kilohms
Input Sensitivity	Unbalanced: 1 V Balanced: 1 V
Signal to Noise Ratio	> 112 dB (IHF-A / Input Shorted) > 107 dB (Input Shorted / Unweighted)

Wi-Fi	No
Bluetooth	No

External Control Support	No
Mobile App Compatible	No

Input Power	110 to 250 VAC, 50 / 60 Hz
Power Consumption	Maximum: 800 W

Dimensions (W x H x D)	17.2 x 4.1 x 15.3" / 437.0 x 105.0 x 388.0 mm (with Feet)
Weight	26.9 lb / 12.2 kg

Package Weight	35.87 lb
Box Dimensions (LxWxH)	21.1 x 20.6 x 11.5"