Parasound A21 Amplifiers

4.93/5 (15 Reviews) MSRP : $1995.00


Product Description

Halo A21 Two-Channel Amplifier
  • Continuous power output (20 Hz - 20 kHz): 250 watts RMS x 2 at 8 ohms, 400 watts RMS x 2 at 4 ohms, 750 watts RMS x 1 (bridged mono mode) at 8 ohms
  • Current capacity: 60 amperes peak per channel
  • Power bandwidth: 5 Hz - 100 kHz, +0/-3 dB at 1 watt
  • Total harmonic distortion: < 0.2 % at full power
  • IM distortion: < 0.04 %
  • Slew rate: >130 V / µsecond
  • Dynamic headroom: > 1.5 dB
  • Interchannel crosstalk: > 80 dB at 1 kHz; > 63 dB at 20 kHz
  • Input sensitivity: 1 V for 28.28 V, THX Reference Level
  • Input impedance: 33 k ohm unbalanced; 66 k ohm balanced
  • S/N ratio: > 112 dB, input shorted, IHF A-weighted
  • Damping factor: > 1100 at 20 Hz
  • Voltage: 110V – 120V
  • Dimensions: 17.25" wide, 7.625" high (7" without feet), 19.12" deep
  • Net weight: 60 lbs.
  • Manufacturer''s limited warranty: 10 years parts, 5 years labor


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    Reviews 1 - 5 (15 Reviews Total) | Next 15

    User Reviews

    Overall Rating:5
    Value Rating:5
    Submitted by Harry a AudioPhile

    Date Reviewed: July 25, 2015

    Bottom Line:   
    My journey to refresh my audio system began with the replacement of my Sonus Faber Grand Piano Domus with the Sonus Faber Cremona Auditor M. After that, it was the DAC (Perpetual Technologies P1/P3 combo) to Wyred4Sound DAC2 DSDse, then my CD Transport (Northstar 192 Transport to Wyred4Sound MS-2 music server), and finally my Power Amp (I ran the DAC direct to the Power Amp). This took the longest as I wanted to make sure that the eventual replacement to my Bel Canto S300 would be a worthy one. Besides equipment, I also changed out my cables (DH Labs HDMI cable from Wyred4Sound MS-2 to DAC, SoundSilver Clarity silver conductor XLR cables from DAC to Amp, & TelluriumQ Ultra Black loudspeaker cables from Amp to Loudspeakers). Hence, it was a total refresh.

    I did my usual research online, and trawled the various online audio magazines for suitable candidates. My requirement for the replacement amp includes relatively high power (more than 300W at 4 ohm), good damping factor, high current capable, reliable, and of course musical and within my budget (not more than $3000). Since my Bel Canto is a Class D amp, I am ok with looking at another Class D amp to replace it, although I did not restrict my search to just Class D amps. That was a good move, because that was when I came across the Parasound A21.

    I am acquainted with Parasound, as my first audiophile quality CD player was a Parasound CDP-1000, and later I bought a Parasound DAC-1500 to upgrade the overall source quality. That was back in 1996. Back to the present time. Over the course of the next 3 months, I went on and auditioned similar priced amps from Wyred4Sound, Bel Canto and eventually the Parasound. I guess it was the fact that the A21 is a Class A/AB design that made the difference (between the Wyred4Sound & Bel Canto). The Class D amps, while very good sounding and good at what they can do for the price, there is a noticeable hardness in the upper registers and frequencies. This became very apparent once I noticed it, and it is present in all recordings and playback. For the A21, no matter how hard it was driven, there was no hardness at all. The upper registers and frequencies sounded sweet and very listenable. In crescendos and complexes musical passages, the amp sounded relaxed and musical. It did not give me any listening fatigue at all. In fact, it made listening to music enjoyable again.

    As mentioned in any other reviews, the A21 does not favor any particular frequency range. He music just came through as it was meant to be. Of course,the quality of the sound is dependent on the quality of the recorded music, as well as the source and ancillary equipment. In my system, the A21 really allowed me to enjoy my music in ways I did not before. The entire system is more coherent and musical than before the refresh. And now Inhabe the added benefit of convenience with the Music Server from Wyred4Sound. Listening to music has never been this fun and easy. I did not miss the cleaning and preparing of my CDs before playing etc. After all, listening to music is supposed to be fun and relaxing.

    In summary, the A21 was the final piece of my equipment refresh journey. It was an apt one, as it truly allowed wonderful music to be played in my new system. For the price, it is an excellent value and, most of all, it does not leave me wanting to look for something better (which I am sure there are for a lot more money). As so many reviewers have said before me, the A21 is a no-brainier and indeed highly recommended! Thank you Parasound for making such a wonderful product at this price point, and bringing musical enjoyment to the masses! I am once again a fan.

    Expand full review >>

    Used product for:   1 to 3 months

    Duration Product Used:   AudioPhile

    Product model year:   2005



    Overall Rating:5
    Value Rating:5
    Submitted by William a AudioPhile

    Date Reviewed: February 22, 2015

    Bottom Line:   
    I have had amplifiers by McCormack, Pioneer, SAE, Odyssey and a few others. This amp by Parasound is head and shoulders better than those amps.

    I had wanted an Odyssey Stratos for many years. But as fate had it, when I got one tI had nothing but problems with intermittent noise and hum. After many, many months of trying to get it fixed I got rid of it. When I took the plunge with the A21, it was massive and quite powerful. But it delivered in a subtle way, as well. It was good with at low volumes and natural sounding at higher volumes. I paired it with a Parasound P3 preamp and it was just.... astonishing.

    The only other amp I heard and liked as much, was a Musical Fidelity integrated dual mono that was twice the price.

    Expand full review >>

    Used product for:   More than 1 year

    Duration Product Used:   AudioPhile

    Product model year:   2010



    Overall Rating:5
    Value Rating:5
    Submitted by sharkman a AudioPhile

    Date Reviewed: October 26, 2014

    Bottom Line:   
    I noticed an earlier review comparing the A21 to an Emotiva amp, and since I owned and reviewed an Emotiva XPA-3 amp back in 2010, I thought I'd review this excellent amp.

    I bought the Halo in 2012, after moving out of a small townhouse and into a largish detached home. I had been using the XPA-3 with Paradigm Signature S6 speakers, a emotiva cd player and their XDA-1 DAC as a pre amp. I'd always watched the volume levels in the townhouse since the side walls are shared with neighbors, so when we got to the house, I was finally able to crank it up, and I mean loud.

    That's when I noticed for the first time that the sound seemed bright, and uncomfortably so. At the moderate levels I'd been using previously and the previous pre amp, an Anthem TLP-1, it wasn't forward sounding, but with the XDA it sure was. Many different solutions were tried, but to make a long story short, after researching Parasound I thought the A21 would be an improvement.

    Was it ever. I compared it side by side with the XPA amp. Using certain tracks, I could get distortion or sibilance when vocalists pronounced an "esss" at volume peaks of 82db. Swap in the A21, same tracks and volume, absolutely no distortion. It was bizzare and repeatable. That's when I noticed that the A21 had nicer highs, and mid range vocals were smooth and detailed like the XPA wasn't. Better bass too, more accurate. I sold the XPA amp. It is a decent entry level amp, and an improvement over receivers, but in the end that's about it.

    The A21 is built like a tank, and images like I'd never experienced. It has many options including variable gain knobs, auto turn on/trigger on, rca outputs, XLR/RCA inputs, and Class A operation for the first 10 watts. Class A is nicer sounding although it is subtle for most. By comparison, the only thing the XPA amp line has is the XLR inputs.

    After some more experimenting, I got their P7. Then I got Audioquest Type 4 speaker cable(in bulk by the foot at $120 for 24 feet.), and Morrow Audio MA3 interconnect cables. Every change brought about an improvement in the end result. The amp has the benefit of having great detail and resolution so better speakers will reward you with air and detail that gives superior imaging than a bargain brand amp. After 2 years, I really feel like it's the last amp I"ll ever buy.

    Expand full review >>

    Used product for:   More than 1 year

    Duration Product Used:   AudioPhile

    Product model year:   2010



    Overall Rating:5
    Value Rating:5
    Submitted by michael a AudioPhile

    Date Reviewed: October 22, 2014

    Bottom Line:   
    Purchased in July 2014. The amp has been around for years. No 21.2, no 21ES.....just the same amp; and there is a reason. This has got to be the one giant killer of sustained value the audio world has ever seen. The power and circuitry are phenomenal. I have played this amp through the Rockport Altairs and the Odyssey Audio Kismet reference. In a word, the flow of music was so evolved and liquid....silky with abundant detail. John Curl is the reason, he designed a unit so evolved that Parasound could get twice the price for it and still be undervalued. Don't hesitate to buy, excellent with every speaker I tried including the Maggie 3.6s. Use the balanced inputs when possible, the filtered power is huge for dynamics and I could swear....it is class A beyond the first 10 watts. I had considered the Pass Labs Int 150, but after reading the review in Stereophile where what appeared to be a faulty unit was given a great review, I passed. Glad I did, I saved a ton of money and received an outstanding amplifier. Using the P5 for a pre-amp and it is as great as the amp is.

    Expand full review >>

    Used product for:   1 to 3 months

    Duration Product Used:   AudioPhile

    Product model year:   2010



    Overall Rating:5
    Value Rating:5
    Submitted by Stharling a AudioPhile

    Date Reviewed: September 28, 2014

    Bottom Line:   
    l bought the Parasound halo a21 and the differences of improvement in the sound quality are just unreal, it's like too good to be true, before the parasound i had an Emotiva XPA and after listened to the differences btw the emo and the parasound i got to the conclusion that emotiva made my speakers sounded so bad, the sound quality is night and day differences, I'm was shocked!! It's just unbelievable, to give you a better hint of what I'm talking about, the emotiva is a Honda and the Parasound is a mercedez Benz s63 AMG, or Toyota vs Ferrari lol. I can't believe the sound just can get that good.

    Emotiva is not High End they not even close to what high end can sounds like, they are good products but never can consider high end, since they claim to be high end, for the price you can get a good sound, but they are out of the high end league, that's a true statement. it's not an opinion It's what it's, when i demo the parasound i put it side by side with 10,000$ and 12,000 dollars amplifiers and the emotiva just sounded as good as those super expensive amps.

    The emotiva was my first amplifier so that's why i wrote a review saying that Emotiva was a truly High end Amp with a consumer price tag LOL, what the Hell i was thinking OMG i was soooooo wrong.

    I was only getting 20% of my sonus faber veneres with the emotiva, now I believe I'm getting their full potential 100%, I believed the hype of the emotiva for a while, I was a believer but now i know emotiva is just a good mid-fi amp, nothing more!! If you looking for the best sound as possible please don't get the emotiva, emotiva is not even close to high end, you will be disappointed!! The parasound is the best High end AMP you can get for the money, i believe that you can spent the double of the money and won't get this kind of performance, Halo is the best Bang for your Buck and i finally found the product that i want to use forever.

    to get a better understanding of what i'm talking about, let's say Parasound vs krell is like mercedez benz S Class AMG vs roll royce!!! all depends your budget and how much money you want to spent, but me personally i'm gonna stick with the parasound halo forever.

    Expand full review >>

    Used product for:   Less than 1 month

    Duration Product Used:   AudioPhile

    Product model year:   2004




    Reviews 1 - 5 (15 Reviews Total) | Next 15

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