Parasound a21 upgrades

Bought a lightly used 2 year old Parasound A21 some days ago. It has exceeded my expectations for sure. Right up my alley warm mids and non aggressive highs but also dynamic and tight with lots of headroom. 
Are there any mods that are reasonable to do to these amps? Fuses etc. Can the bias be safely increased to add more class a watts? 
Also have there been any changes over the years? So is a 2 year old A21 the same as a 15 year old one? 

Hi there!
I owned two of these in a home theater set up. I agree with your description, but I want to encourage you to absolutely leave it alone. This is a gateway amp for many people. Yes, it’s good, but it’s good in a way that makes you look for even better, evidenced by your desire to mod them already.

Leave them alone and trade up when you have to so you can preserve the resale value.

As for the bias, I did some power measurements on them at idle. They already run hotter than spec, and I suspect they are already biased warm, do not adjust.

The only mods I might encourage you to try are to build your own IC and power cables. The amp’s XLR inputs are convenience, not real so don’t force yourself to use balanced IC’s.
I’d recommend using DH Labs shielded power cables, and pure silver IC cables with KLH plugs. See what you learn.
Of course, if you are just getting into high end audio, I always encourage you to invest in room acoustics as early as possible.
Thanks Eric,

Just for my own curiosity what would be an amp that you would see as a clear upgrade to the A21 not priced in the stratosphere. Similar power specs let's say 6k or under new price. 
The latest version is the A21+, maybe Parasound can tell you what's different and maybe they have an upgrade program. 
Hi OP :

Luxman and Ayre are brands you should listen to which you can find in that price range used.

The JC5 is the clear upgrade at 6k, one could argue go for the A21+ and save some coin as from what I understand it's a refined A21. I switched to the JC5 after many years of musical enjoyment with my A21, I did upgrade it's main fuse twice with fantastic results , one was the HiFi tuning Silver Star and a few years later the Supreme. I do however recommend the Xlr's and a good powercable  of choice. And as noted above if your room isn't acoustically treated do so.

Thanks all,

As I said I am very happy at the moment with the stock A21 so won't be upgrading in the near future. I'm sure at some point the bug will bite! Ussually sooner than I'd like. 

I may look into the hifi tuning fuse. I am ussually very skeptical of such things but for 100 buck would not be out a whole lot and I can make my own determination. 

I agree since I very much like the basic sound signature of the A21 the JC5 may be a clear path. At least from a risk standpoint. In your mind was it worth the extra cost? 
For a single box a JC5 for sure. Mono’s JC1s. I agree with Eric, PC’s are a great add Parasound gear seems to like Shunyata power. Not much else really. You are getting into the price realm when there are so many great options, it’s really tough to nail them down. The A21 is an excellent amp.
@erik_squires, if memory of your prior posts serves, I thought you have previously owned the Parasound A23, which sells for about half the price and has about half the watts of the A21 the OP has purchased.

Where the A23 could be considered Parasound’s entry into their higher end line, not so the A21. Whether you care for the warm sonic voicing of the amp is personal preference.  Note that the A21 remained unchanged for 17 years before the upgrades performed in 2020 resulting in the name change to A21+.
what preamp are you using?
a great way to upgrade your amplifier is to upgrade your preamplifier.  
balanced cables could benefit too depending on your preamp.  
I'm running RME ADI-2 dac directly into the amp. Also tried with my upgraded Joida Pre and prefer direct for sure. I only do digital so I see no need for a preamp. 
I tried balanced and unbalanced and heard no difference which makes sense since I believe the A21 is not truly balanced. 
a common approach for sure but until you try one you will not understand the impact a preamp with gain stage has on overall sound.  
your amp is not at its full potential until it receives a powerful, dynamic signal which requires gain.  
having had several amps and preamps as well as integrated amps with passive preamps, a quality preamp can literally wake up a sleepy sounding amp.  it is much more than a source switcher.  
even though the a21 is not balanced, it will take advantage of balanced preamps which offer more gain with lower noise.  
this is the best way to take your system to a much higher level even though your direction is a different approach currently.  

I was in the same boat.  I had both A21 and several JC1.  The A21 has 5 fuses that affect sound quality (1 on back panel and 4 internal).  I could never get the amp to sound good regardless of what fuse I tried because it deviated too much.  You could try Audiomagic Super Fuse (which is almost a better version of stock).

A power cord upgrade is good.  Other than that, you are better off switching to a different amp like others have suggested.
re, preamps, especially a tube based preamp.  
power cords did zero for my a21, two made the sound worse.  
Thanks for the suggestions. I think I will take Eric's advice and leave it alone. I do really like the amp. Added dedicated 20a circuits today. Nice improvement! 
If you haven't already, you might try some vibration control.  Just three Stillpoints minis, for example, will provide a very significant sonic improvement.  And then you can go down that rabbit hole instead of spending more on a new amp :)
Right up my alley warm mids and non aggressive highs but also dynamic and tight with lots of headroom.
What more can you want, John Curl's not an idiot, if he thought a "snake oil fuse" would make a difference for the better again he would have put it in.
Don't listen to these "fuser twits" here, they have absolutely no idea, and that's about their technical skill limit, to change a fuse, so that's all they will do and comment on.

Cheers George  
Agreed. Like I said I very much like the amp. I'm sure multiples in cost would likely bring an improvement. I'm good to go for a "long" while. I think. Dedicated lines today are a big improvement"no sh.t. and the longer I listen not snake oil. I had nasty s**t on those lines. 
Ha  ha says one twit . 
In a thread on Audio Asylum , we had a great discussion a few years back with Mr. Curl who said if given the choice he would've used silver fuses in the  Halo amps, I used the Silver Star in my A21 and the results kicked up several notches in refinement across the spectrum , there was a reason I kept the A21 around for 12yrs , it just flat out sounded so good!
I have been an A21 owner for about 9 years now, lthough I upgraded two years ago to a Plinius SA-103. It was almost three times the cost of a good used A21 at the time and still well under your future budget.  Even though the SA-103 can be switched into full time Class A mode I still find myself listening in Class AB most of the time.  It was a a worthy upgrade.  I had been driving the A21 for those first 7 years with an Aesthetix Calypso.  Last year I updated the Calypso to the Signature level along with a good set of NOS 60’s and 70’s tubes.  I feel no desire or need to update either the amp or preamp.  
jdub3 In a thread on Audio Asylum , we had a great discussion a few years back with Mr. Curl who said if given the choice he would've used silver fuses in the Halo amps, I used the Silver Star in my A21 and the results kicked up several notches in refinement across the spectrum , there was a reason I kept the A21 around for 12yrs , it just flat out sounded so good!
Prove it with a link to it, AA retain all links.

Sorry! typical fuser, you quoted it, so prove it.
It’s bs if you don’t or can’t, simple as that.

Manufacturers will make a product if it's easy to switch out.

Cables, fuses, power cords. 

As mentioned earlier, don’t do any internal mods as you have a nice amp. Some simple things are use a good heavy gauge high current power cord so you don’t starve your amp. If you’re using a $2 spec grade wall receptacle, upgrade that with something with better contact pressure to a Hubbell hospital grade outlet, which you don’t have to break the bank on that. Next if you’re really looking for an improvement and own your home, run a dedicated circuit or two your system. Isolation isn’t a bad thing to work on including your rack, but something simple and affordable are Cardas myrtle blocks… they work.

If you really want to improve you’re system, since you’re running your RME direct, is toss the switch power supply and get a Teddy Pardo, SBooster or other linear power supply as this will make a big difference. 


Room treatment is also a smart move but most don’t want their room, especially if a great room or shared living area looking like a recording studio but it is probably the place to start or your chasing your tail. Great amp… enjoy it.