Усилители мощности стерео — Parasound HALO A23+

The HALO A23+ is a Parasound stereo power amp, the updated version of the earlier A23 in the HALO range. Its circuit comes from John Curl, the designer behind the HALO power amplifier platform, and runs with high bias in Class A/AB. Without its feet the chassis is 89 mm tall and fits a 2U rack space, and the current list price is USD 2,500 with black and silver finishes on offer.

Key specs that matter

Parasound rates the A23+ at 160 W per channel into 8 ohm and 240 W into 4 ohm, both at 0.06% THD, with 210 W and 300 W available at 0.9% THD. Bridged into mono it gives 500 W into 8 ohm, while bridged 4 ohm loads are not recommended. Response runs from 5 Hz to 100 kHz within 3 dB and stays within 0.25 dB across 20 Hz to 20 kHz. Distortion falls under 0.03% at typical listening levels, IM distortion is under 0.04%, and signal to noise exceeds 112 dB A-weighted (107 dB unweighted). The damping factor exceeds 800 at 20 Hz, slew rate exceeds 130 V per microsecond, and gain is 29 dB. The case measures 438 x 387 x 105 mm with feet and weighs 12.2 kg.

Engineering and use context

The supply is built on a 1.1 kVA shielded toroidal transformer with separate windings for each channel, feeding 54,400 uF of filter capacitance in the output stages. Twelve beta-matched bipolar transistors rated at 15 A and 60 MHz form the output stage and can deliver 45 A peak per channel. The signal path is direct-coupled, using JFETs at the input and MOSFETs in the driver stage. A DC servo, relay protection and AC inrush limiting guard the amp and the speakers. Balanced XLR inputs present 66 kohm and gold-plated RCA inputs present 33 kohm, and 1 V on either reaches full output. Rear-panel level controls allow gain matching, a looped RCA output feeds the same signal to another amplifier, and turn-on can follow a 12 V trigger or audio sensing between 2 and 10 mV.

Pairing

The gain controls and loop output make it simple to add a second A23+ for bi-amping or to run two bridged units as monoblocks for speakers without low impedance dips. Any preamp or streamer with a volume control that can drive the RCA input load will fit, and the XLR inputs suit preamps with balanced outputs. From September 2026 Parasound gives three years of cover for parts and labour on this model. The front panel stays plain, so the amp can sit out of sight in a rack once the feet are taken off.

Alternatives

The Parasound HALO A21+ is the larger stereo power amp from the same designer, rated at 300 W and 500 W per channel into the same two loads, with 60 A peak current per channel.