Plus sizes — Parasound announces more powerful 'plus' versions of their A 21 and A 23 power amplifiers in continuous production since 2003. The new Halo A 21+ [$3'149] and A 23+ [$1'495] employ higher-capacity power supplies to increase output power. This targeted power supply transformers and filter capacitors as the foundation for power output increases. Further refined also is audio quality in the signal-path and related circuitry with upgraded gold-on-gold internal connections to improve resolution and increase transparency. With its larger 1.3kVA power transformer and 108'000µF power supply capacitance, the Halo A 21+ jumped from 250 to 300 watts into 8Ω, 400 to 500 watts into 4Ω and from 750 to 1000 watts in bridged mode. Further improvements increased signal-to-noise ratio from 112dB to 115dB, crosstalk from 63dB to 70dB while THD at full rated power output has decreased from 0.2% to 0.1%. These improvements pushed net weight over 18% from 60 to 71 pounds. Like the original A 21, the new A 21+ amplifier gives users a choice of balanced and unbalanced inputs with loop outputs and variable gain controls. The most visible rear-panel difference on the A 21+ are new CHK Infinium heavy duty speaker terminals originally developed for the top-of-the-line 400wpc Halo JC 5.

The new Parasound Halo A 23+ is similarly improved with a larger 1.1kVA power transformer and 54'400µF power supply capacitance. This supports increasing power output from 125 to 160 watts into 8Ω, 225 to 240 watts into 4Ω and from 400 to 500 watts in mono bridged mode. The A 23+ has balanced and unbalanced inputs with adjustable gain controls, loop outputs and new higher-performance speaker terminals adapted from the popular Parasound HINT 6 integrated amplifier. Both new amplifier models feature more-refined Halo styling including solid aluminum end caps with gold highlights. Both models include 12-volt DC triggers with loop outputs plus more sensitive audio auto turn-on.