Parasound Halo A21+ Stereo Power Amplifier Review

This powerful class A/B stereo amplifier is an updated version of the highly popular Parasound A21. In today’s world, upgrades get the obligatory “+” sign added to the model number. This “+” signifies it is an improved version of a prior model.

Parasound, the company, sold during the time of my review cycle. I asked the new leadership team for details on what changes were made over the prior model. They were not able to provide any significant details outside what was published on the company website. The below bullet points were copied from the Parasound website:

Changes from the original A21 to A21+

Despite the list above being silent on the details regarding precisely how these specs were improved, we do know that the new version has a larger transformer and more filter capacitance which would stand to reason considering the increase in claimed power output. The new amplifier is heavier as well.

All other bullet points speak for themselves with one exception. I am not sure if “Upgraded internal gold on gold audio connections” means that the older unit had gold on gold connections that have been updated or if the connections have been updated to gold on gold from something else. The mystery deepens.

From a practical standpoint, the amplifier does have some important functionality bonuses. To begin with, I did like the new binding posts and if I used bare wire or spades, I think I would be smitten by the winged posts. However, like most professional reviewers, I use banana plugs almost exclusively.

Take a look at the rear panel. The amp has balanced XLR or unbalanced RCA inputs with an unbalanced pass-through on each channel in the event the user wishes to daisy-chain these amps. I can’t imagine who would ever *need* more than one of these amps provides and, if they did, why not vertical bi-amp or bridge them instead? I think the most common use of the pass-through would be to feed the signal to a subwoofer or two. In my book, that is the most likely use for this feature.

One feature I really liked and used often was the gain control for each individual. channel. I like this because not all preamps have a balance control and, in my setup, I routinely sit off-center. These controls allowed me to center the image no matter where I was sitting in the room. My lingering problems with this are two-fold: First of all, Parasound did not provide any details on how these gain controls are implemented. They might be simple potentiometers which raised my second concern – why can’t they be bypassed for the greatest fidelity possible when not being used?

The back panel also contains several power-control capabilities. It can be manual-on, signal sensing On/Off, or 12V trigger On/Off with pass-through. These are welcome features, particularly in a complex system or a home theater environment.

I also mused about the protective fuse and how it is implemented.

The review unit I got was silver and the build quality was acceptable. The unit had a nice heft, and the front and back panels were substantial with high-quality switches, etc. It can be hard to see in the photos, but the heat sinks were made from two parts per side that were bolted together. In person, this was not a seamless build. Also, the outer shell of the case felt like stamped metal. These two things gave the amplifier a bit of a mid-fi feel and if I owned one of these amps, I would probably mount it in a rack so all you see is the front.

I want to close this section by saying that I had my bench testing rig up and running when I reviewed this amplifier, but I ran out of time when the new owners requested, that I send the amplifier back despite the fact that I had not completely finished my evaluation. So, I was not able to independently verify their stated specifications. In defense of Parasound, I did have the amplifier for longer than usual because of life issues and all that, but I would have appreciated a few more weeks to button up my review work. The review sample is safely back in their hands now, whew.

I placed the amplifier on a new amp stand between my speakers in the front of my listening room. It was simple enough to set up. I ran the unit both balanced and unbalanced during my evaluation. The interconnects and speaker wires were Clarus Crimson. I also employed a Clarus Crimson power cable but no power conditioning – the unit was plugged straight into the wall.

The primary speakers used during the evaluation were my beloved VIVID Kaya 90’s. I also used the amp with a pair of Klipsch RP-8000F-II tower speakers I had in for review. I used both a passive preamp and alternately I used a tube preamp based on 12AX7 and 12AU7 tubes. Sources were an Oppo BDP 105D player and a Raspberry Pi (as a Roon endpoint) both running through a Topping D90 DAC. On the analog side, it was my MoFi Ultradeck with a Mastertracker MM cartridge being manipulated by a Pass Labs XP17 phono preamplifier.

The entire Parasound Halo line has been a huge success among audiophiles around the world. One might say they are certified ubiquitous in the hi-fi and home theater worlds. You don’t get this big and important without solid performance and that is exactly what I got. Let’s dive into my listening impressions right off the top –

I also sensed that the A21+ had a ton of reserve power and headroom. This was realized by way of the amplifier being in control of the proceedings. Furthermore, I noted that the performance was laid out with an ease and grace indicative of an amplifier working well within its design envelope. I also commented on how the treble went on seemingly forever.

The song that stood out the most for me was Comfortably Numb with its very slow and ethereal rollout sans any guitar solos. Even listening at reasonable volume levels, this song presented as a whole-body experience. It was incredibly musical and again the A21+ didn’t even work up a sweat so everything was clean and tight. I also enjoyed the vocal harmonies where I heard individual voices and not a mass of them. This was very well done by the Parasound amp.

Even in my 2-channel setup, I find myself enjoying concert videos on Blu-Ray from time to time. In this case, I auditioned a Blu-Ray on my Oppo BDP 105D which fed the video signal directly to my display but with the stereo audio track going via an optical connection to my Topping D90 DAC. The concert video in question was Sade’s “Bringing Me Home Live 2011”. I have always loved Sade and this concert was the cat’s meow.

I was glued to the system throughout the concert’s approximate 2-hour runtime. I enjoyed every note but also couldn’t shake the feeling that I was hanging out with the cool kids for a couple of hours. The overall excellent production quality really highlighted the musical aspects of the experience. The Parasound A21+ made it all that much better. My notes are littered with all sorts of audiophile keywords and phrases: purity of tone, dynamics, percussion, fluid bass lines, and on and on.

All in all, I had not one criticism of the performance laid down by the Parasound A21+. It was in fact a very competent performer that I could easily live with for the rest of my natural days.

The Parasound Halo A21+ stereo power amplifier is a powerful, solid-state stereo amplifier that performs with excellent musicality and accuracy. It could have improved build quality, however.

The Parasound Halo A21+ amplifier impressed me with its powerful, musical, and accurate reproduction of music and movie soundtracks. This amplifier had wayyyy more power than I could ever need as well. The performance I heard was beyond reproach and I didn’t hear any untoward sounds the whole time it was in my system.

In terms of implementation, the Halo A21+ was well-made in most respects. My only quibbles are the stamped metal cover and the two-piece heat sinks. These parts fell short of a high-end build in my view. However, they did not take away from the very flexible hook-up options and apparent protection circuitry. These features render the amplifier very useful in a wide range of settings.

My final conclusion is to buy this amplifier for its flexibility and performance qualities over the build decisions. The price of this amplifier has been raised recently but it is still well worth every penny you spend on it. Recommended for sure!