Parasound A21 Amplifiers

4.92/5 (13 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


  • Review Options:  Sorted by Latest Review | Sort by Best Rating

    Reviews 1 - 5 (13 Reviews Total) | Next 15

    User Reviews

    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



    Overall Rating:4
    Value Rating:5
    Submitted by MagnusVer a Audio Enthusiast

    Date Reviewed: June 11, 2011

    Bottom Line:   
    The A21 has got to be one of the best kept secrets ever. I bought it second hand for less than half the original retail price. Wonderful performance driving any speaker load, and I've run it with seven different speakers thus far, both conventional and planar.

    The amp is like a diesel engine, pulling an incredible amount of low-end grunt from recordings where I had formerly never known it existed. It has been a tremendous pleasure going through my old dust covered disc collection discovering some real hidden gems I'm glad I hadn't discarded.

    It is definitely a beast of an amp physically, and proper space is needed if that is a concern in your application. You'd better allow for about 22" of depth if you use XLR's.

    I had a McIntosh MC7200 at the same time as the A21, and after over a year of comparison I sold the Mac. The A21 just trumped it in every way. Though I did like the blue VU meters on the Mac...

    One small negative is the XLR sockets do not have a locking feature. Other than that this is one of the best amps available for the money bar none. Buying one second hand is a classic no-brainer. This one is a keeper.

    Expand full review >>

    Used product for:   More than 1 year

    Duration Product Used:   Audio Enthusiast

    Product model year:   2008



    Overall Rating:5
    Value Rating:4
    Submitted by cocopeep a AudioPhile

    Date Reviewed: June 9, 2007

    Bottom Line:   
    The parasound Halo A21 is a heavy amplifier. Great quality looks and build, handles on the back and heat fins on the side, the blue lights look good at night. 250 watts per channel, it has plenty of power to run inefficient speakers, such as my JSE infininite slope 1.8 with 4 drivers. Using Cardas quadlink speaker and interconnect, this needs a good break in period and open cabinet where the heat can escape. After many hours of playback, the soundstage opened up with instruments heard in great detail. With 1.2 kVA encapsulated toroid power transformer with independent secondary windings for each channel , and 100,000 µF power supply filter capacitance , this amp delivers superb bass, this amp will never break a sweat! This one amp will outperform my 2 B&K ST202 put together in a bi-amped setup.

    Expand full review >>

    Used product for:   Less than 1 month

    Duration Product Used:   AudioPhile

    Product model year:   2004

    Price Paid:    $1600.00

    Purchased At:   longplayer stereo Go




    Reviews 1 - 5 (13 Reviews Total) | Next 15

    Review Options:  Sorted by Latest Review | Sort by Best Rating


    The Sugden A21-a

    My local dealer has a Sugden A21-a integrated for sale... Now this amp is rated at 25w 'pure class A' and it sounds fantastic with the speakers he has at the showroom (Tannoy's and Kef) but i dont know whether this will match the Paradigm studio 20? I have read a lot of reviews on this amp, but no o ... Read More »

    150 watt JM Chorus speaker powered by 250 W Halo A21

    Hi guys, Im thinking about buying a new pair of JM Labs 726 V speakers I listened to at my local dealer. These speakers are rated to handle about 200-250 watts. My Parasound Halo A21 amp puts out 250 watts @ 8 ohms and I am running those into a pair of JSE Infinite slope 1.8 that can handle 300 wa ... Read More »

    Parasound A21 or A23?

    Hello anyone interested in reading... I am curious to hear some thoughts about the following situation. Right now I am powering my PSB Platinum T6's with a Parasound Halo A23, which has been a great combination, but I am also quite aware that my speakers are in need of a bit more power to really ... Read More »

    Halo A21

    Does anyone else know of some similar amps to that of PARASOUNDS HALO A21? I am shopping around for some similar ones to compare it to.Read More »

    how about Sugden A21 and PMC TB-2S

    Dear all, i am the entry-level AVer. just think about to buy a used AMP + SP. my picked the sugden A21 (A class) plus PMC TB-2S(old version). When listening the jazz vocal and pure music ..... i felt very easy... not in rush..i can walk around(it might be a bad habit)... just wanna know ... Read More »

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