ParaSound Halo A21 vs Nad M25

Hi Audiogon -

I have a question about the performance of certain amplifiers. The ParaSound Halo A21 vs Nad M25.

Im assuming the ParaSound outperforms the Nad M25 by a mile due to its more wattage output and 1100 damping factor compared to 180 on the Nad. However wanted to get a professional's take on the matter. I have 6 ohm speaker fronts I want to drive to obtain cleaner power, better bass seperation, and better midrange and treble and the sorts. Right now I am using an denon 4308 for pre amp and amp and can tell the denon is pushing to obtain adequate outtage.

Any help on this matter would be helpful. If you need any additional information regarding this issue please ask.

Eihter one of the amps mentioned will easily out-perform the amps in the Denon. I wouldn't worry too much about the damping factor numbers, once you get past a factor of 100 or so it really doesn't make much difference.

I would consider the efficiency of the speakers and the sound pressure levels you wish to achieve as being more important specs. for you to consider.

As an example, I am driving my Gallo Reference 3.1 speakers (88 db efficiency) with a Butler TDB-5150 5-channel tube amp with 150 watts/channel (into 8 ohms, 225 watts into 4 ohms) and it gets *plenty* loud enough for me.

In fact, you may want to consider buying a Butler for your application, it will provide you with the sweetness of tubes coupled with the "balls" of a MOSFET amp:

Finally, you may want read this whitepaper about amplifier damping factors, it will dispel some common mis-conceptions that many folks have about it:

Good luck!


Thanks for the reply and help.

My speakers have an effciency of 91.5 I believe. They are Dali Ikon 7's so they are really easy to drive. I just feel the Denon amp section is the dragging the Dali Ikon's to "mid-fi" level, as the dali bass at high volumes is muddy sounding.

What sort of improvements would be heard if I get myself a ParaSound Halo A21.
I have heard the Parasound Halo A21 on numerous speakers at numerous dealers and it is an amazing amplifier, let alone for the cost even at full retail of about $2,300. it does offer a true class A up to about 7.5wpc (straight out Richard Schram's Email to me about this amp) and is beautiful sounding. I could recommend it for many systems or applications so easily and with no reservations at all. In fairness, I have not the NAD model, but for what I have heard in the A21, I thoroughly enjoyed it every single time. What Rlwainright said about the damping factor getting above 100 or so is true. All the damping factor is is the ratio of the power amp's. output imedance to the input imedance of the speaker at a given frequency. That then has a strong impact on how well the amplifier functions as a constant voltage source despite varying current loads and that in turn impacts the amplifier's ability to control the load (cones / diaphragm, etc.). Higher is always better in general though, especially at a very low frequency, such as 20Hz, since bass draws more current than treble, etc. Hope that helps. Parasound A21.
Hello to all I have a Parasound a21 ampliifer and I can tell you for a instant upgrade there are 5 fuses a 12a T
30mmL on the back ,and 4 8aT 30mmL inside the amp You spend the $450 or less with discounts of the Hifi tuning Supreme fuses ,this and a Very good high current power cord ,Nothing cheap, and you now have a solid 10% + at least improvement across the board .The fuses take a solid 48 hours to settle in after day 3 fantastic the fuse are directional on the back fuse put that in facing the front,
the other 4 internal fuses from the transformer to the capacitors or all arrows facing the rear .and do take some 90% Isopropyl alcohol to clean the fuses contacts
or caig pro gold .You won't believe the added resolution
clarity or added musicality .forget the Money $$ outlay
it is less than a set of decent interconnects and it is the biggest improvement per dollar out there !!
I know this is an old thread, but I believe the fuse directions are reversed. I tried them both ways a few times and much prefer the fuse on the back pointed out and the internal fuses pointed toward the front. It is much more extended and clear this way for me. Therefore, I would recommend trying them both ways.
Hello Audioman58,
I have recently replaced both the main and the 4 rail stock fuses of my Parasound A21 amplifier with Hifi tuning fuses. I replaced these fuses in sequence. First replaced only the main fuse by Hifi Tuning Silverstar fuse and it immediately improved, while breaking in, the sound in all areas.
Then I replaced the 4 rail fuses with Hifi Tuning Gold fuses (couldn't get the Silverstar in 8A) with arrow pointing to the flow of the current i.e pointing from the transformer to the capacitor. The result wasn't so impressive. While it increased the clarity but the instruments started sounding very hazy and smeared. The overall sound was also veiled. It has been 20 odd hours since I replaced the internal fuses and they might still be going through the break-in interval. I tried flipping the fuses such that they point to the transformer to see if that resolves the haziness but it didn't.
Did you have similar experience when you replaced the rail fuses inside the Halo A21? You have mentioned a 48 hrs break-in period for the fuses. Did you have similar experience during the 48 hour break in period? Any feedback/help in this regard would be really appreciated.