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What Is a Stereo Power Amplifier — and What Does the A23+ Do?
A stereo power amplifier is the muscle of your audio system. It takes the small audio signal from your preamp (or the pre-out section of a receiver) and amplifies it with enough power to drive your speakers. Without a good power amp, even the best speakers can sound flat and lifeless.
The Parasound Halo A23+ is a two-channel (stereo) power amplifier that delivers 160 watts per channel into 8-ohm speakers, or 240 watts per channel into 4-ohm speakers. If you need even more power for a single speaker or subwoofer, you can bridge it into mono mode for a substantial 500 watts. It sits in a slim, rack-mountable chassis that’s only 2U tall (about 3.5 inches), so it won’t take up much space on your shelf or in your equipment rack.
The A23+ is the upgraded successor to Parasound’s hugely popular Halo A23, which held a spot in the company’s lineup for an impressive 17 years. This new “Plus” version brings a 25–30% increase in power output, a beefier power supply, improved internal components, and refreshed cosmetics — all while keeping the same compact form factor.
Why Does This Amplifier Stand Out?
The A23+ was co-designed by John Curl, one of the most respected audio circuit designers in the industry. Curl has been working with Parasound since 1989, and his designs are found in professional recording studios around the world, including those at Lucasfilm, Pixar, and Sony Pictures. When an amplifier’s circuit designer has credits like that, you know the engineering is serious.
The A23+ uses what Parasound calls a “high-bias Class A/AB” design. Here’s what that means in plain language: Class A amplification is widely considered to produce the purest, most natural sound, but it generates a lot of heat and isn’t very efficient. Class AB is more efficient but can introduce slight distortion at certain points. The A23+ blends both approaches — it runs in Class A at normal listening levels (where sound quality matters most) and smoothly transitions to Class AB only when you need higher power for loud passages. The result is natural, detailed sound without the excessive heat of a full Class A design.
The signal path is “direct-coupled,” meaning there are no capacitors or inductors between the input and the speaker terminals that could color or degrade the signal. The amplifier uses discrete JFET transistors at the input stage (chosen for their low noise), MOSFET transistors in the driver stage (which help reduce harsh-sounding distortion), and twelve fast bipolar output transistors per channel that can deliver up to 45 amps of peak current. That high current capability means the A23+ can comfortably drive demanding speakers, including models whose impedance dips below 2 ohms.
The power supply is equally impressive. A custom 1.1 kVA shielded toroidal transformer with independent windings for each channel provides quiet, stable power. The total filter capacitance is 54,400 µF — a 35% increase over the original A23 — which helps the amplifier deliver fast, controlled bass and dynamic impact during loud, complex passages.
What Are Reviewers Saying?
Sundaram found the A23+ offered impressive clarity, precision, and well-balanced tonality across a range of musical genres. He noted the amp’s excellent dynamics, its ability to portray fine instrument details, and the fact that it consistently outperformed his reference integrated amplifier. He concluded that Parasound provides outstanding value in the A23+ and praised its build quality as well as its sound.
SoundStage! Access — Reviewer’s Choice
Sathyan Sundaram — July 2019
The A23+ has earned strong praise from several respected audio publications. Sathyan Sundaram at SoundStage! Access awarded it a Reviewer’s Choice designation in July 2019, noting the amplifier’s impressive clarity with orchestral recordings and its ability to reproduce fine details in small-combo jazz. He found that the Parasound consistently outperformed his reference integrated amplifier in terms of energy, definition, and soundstage precision.
Dr. Go described the A23+ as delivering neutral, vivid sound with excellent dynamics and a well-balanced frequency spectrum. He found the treble extended, the bass punchy, and the soundstage portrayal satisfying. He praised the amp’s build quality and stylish appearance, noting that it always felt in control of the music during his listening sessions.
Secrets of Home Theater and High Fidelity
Yongki Go, Ph.D. — November 18, 2020
According to Yongki Go, Ph.D., writing for Secrets of Home Theater and High Fidelity in November 2020, the A23+ delivers a neutral, vivid sonic character with excellent dynamics and a well-balanced presentation across the full frequency range. He praised the build quality and noted that the amplifier always seemed in firm control of the music.
Solstad tested the A23+ alongside the Parasound P 6 preamp and was highly impressed by the combination, praising its dynamics, rich midrange, and resolution. He considered the performance remarkably competitive for the price.
Stereo+ (Norway)
Roy Ervin Solstad — January 2019
Roy Ervin Solstad at Stereo+ (Norway) tested the A23+ alongside the Parasound P 6 preamp in January 2019 and was deeply impressed by the pairing, describing the combination as having outstanding dynamics, a rich midrange, and strong resolution at a price point he found remarkably competitive.
The Spanish publication highlighted the A23+’s ability to reproduce a wide sonic palette with depth and micro-level detail. They praised its bass reproduction particularly, noting the amp brought out the best low-frequency performance from their speakers across various musical genres.
ON-OFF (Spain)
September 2019
The Spanish publication ON-OFF also reviewed the A23+ in September 2019, highlighting its ability to reproduce a wide range of sounds with depth and fine detail, and noting particularly strong bass performance.
In a detailed follow-up review, Dr. Go found the A23+ to be solidly constructed with balanced sonic characteristics and good presentation of musical details. He noted its sense of space, imaging, and soundstage were strong, and that the amplifier always seemed in firm control of the music regardless of complexity.
Home Theater HiFi
Yongki Go, Ph.D. — February 2022
Across the board, reviewers consistently praise the A23+ for offering a level of sound quality and build quality that’s hard to find at this price point.
Who Is the A23+ Best For?
You’re building a dedicated two-channel stereo system and want a separate power amplifier that punches well above its price class.
You already have a preamp or processor with pre-outs and need a clean, powerful amplifier to drive your speakers.
You own speakers that are moderately difficult to drive (4-ohm or lower impedance) and need an amp with high current capability.
You’re looking for a compact, rack-mountable amplifier that doesn’t sacrifice sound quality for a small footprint.
You want a versatile amp that can run in stereo for music or be bridged to mono for powering a single speaker or subwoofer with authority.
How Does It Connect to Your System?
The A23+ offers both balanced XLR and unbalanced RCA inputs for each channel. Balanced connections are generally preferred in high-end audio because they reject noise more effectively — if your preamp has balanced outputs, use them for the cleanest signal. Using balanced XLR connections also provides a 6 dB higher volume level compared to RCA.
On the output side, you get heavy-duty, 24k gold-plated five-way speaker binding posts that accept banana plugs, spades, or bare wire. There are also RCA loop outputs that pass the input signal through, which is handy if you want to daisy-chain a second amplifier or connect a subwoofer.
The rear panel includes per-channel gain controls (useful for level-matching in multi-amp setups), a 12V trigger input and output for automated turn-on/off, and an audio-sensing auto-on feature so the amp can power up automatically when it detects a signal from your preamp. There’s also a “Vacation” master AC switch for completely disconnecting power when you’re away for extended periods.
Keep in mind: The A23+ is a power amplifier only — it does not have a volume control, source selector, or built-in DAC. You’ll need a separate preamp, integrated amplifier with pre-outs, or a surround processor to control it. If you need help figuring out the right companion components, give us a call — we’re happy to help.
Pairs Well With
Building your system? Here are some great companions for the A23+.
Preamps: The Parasound Halo P 6 is the natural partner — multiple reviewers tested them together and praised the combination. Browse our full selection of Preamplifiers.
Speakers: With 160 watts per channel and high current output, the A23+ can drive everything from bookshelf monitors to full-size floorstanders. Explore our Bookshelf Speakers and Floorstanding Speakers.
Cables: To get the most from your balanced or unbalanced connections, check out our XLR Interconnects, RCA Interconnects, and Speaker Cables.
Furniture: Need a solid rack to support your components? Browse our Audio Racks — the A23+ fits standard 19” racks with an optional Parasound HRA 2 rack mount kit.
Power Products: Clean power helps any amplifier perform its best. See our Power Products for conditioners and cables.
Frequently Asked Questions
Do I need a preamp to use the A23+?
Yes. The A23+ is a dedicated power amplifier — it doesn’t have its own volume control or source selector. You’ll need a separate preamp, an integrated amplifier with pre-outs, or a home theater processor to control it. The Parasound Halo P 6 is the most popular pairing, and multiple reviewers have praised that combination. If you need help choosing, give us a call at 800-942-0220.
Can I use the A23+ for home theater?
You can. Many people use the A23+ to power their front left and right channels in a home theater, connected to the pre-outs on their AV receiver or processor. You can also bridge two A23+ units into mono for even more power on the front channels, or use one to power a subwoofer.
What’s the difference between the A23+ and the bigger A 21+?
The Halo A 21+ is Parasound’s flagship two-channel amp, delivering 300 watts per channel into 8 ohms (compared to 160 watts for the A23+). It has a much larger chassis, heavier power supply, and even higher current capability. If you have very demanding speakers or a very large room, the A 21+ is the way to go. For most setups with bookshelf or mid-size floorstanding speakers, the A23+ provides more than enough power and sound quality at a lower price and smaller footprint.
Should I use the balanced XLR or unbalanced RCA inputs?
If your preamp has balanced outputs, use the XLR connections — they’ll give you lower noise and a 6 dB gain advantage. If your source only has RCA outputs, the unbalanced inputs work great too. Just make sure the Balanced/Unbalanced switch on the rear panel is set to match whichever input type you’re using. Don’t connect both types at the same time.
Can I bridge the A23+ into mono mode?
Yes, and it’s a popular option. In bridged mono mode, the A23+ delivers 500 watts into 8 ohms — that’s serious power for a single speaker or subwoofer. Keep in mind that bridged 4-ohm operation is not recommended. If you want mono power for a stereo pair, you’d need two A23+ units.
Does the A23+ need time to warm up before it sounds its best?
Not really. Parasound’s exclusive bias circuit is designed so the A23+ sounds right from the moment you turn it on. Unlike some amplifiers that need 20–30 minutes to reach their optimal bias point, the A23+ is ready to go immediately.
How does the auto-turn-on feature work?
The A23+ gives you three turn-on options, selectable via a rear-panel switch. “Manual” means you press the front button. “Audio” means the amp powers up automatically when it detects a signal from your preamp, and powers down when the signal stops. “12V Trigger” means it turns on when your preamp or processor sends a 12-volt trigger signal. The audio and trigger modes are great for multi-room or home theater systems where you want everything to turn on and off together.
Will the A23+ fit in my equipment rack?
The A23+ is 2U tall (3.5 inches without feet), so it fits neatly in a standard 19-inch equipment rack with the optional Parasound HRA 2 rack mount kit (sold separately). It also works great sitting on a shelf or audio rack.
What speakers pair well with this amplifier?
The A23+ is versatile enough to drive a wide range of speakers. Reviewers have tested it successfully with everything from compact bookshelf monitors like the Sonus Faber Principia 3 to larger speakers like Magnepan 1.7i panels and KEF R3 bookshelf speakers. Its high current output means it won’t struggle with difficult loads. If you’re unsure whether the A23+ is the right match for your speakers, call us and we’ll help you figure it out.
What warranty does the A23+ come with?
Parasound backs the A23+ with a 5-year parts and labor warranty (2 years for moving parts, remote controls, lasers, displays, and video screens). You can view the full warranty details here.
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