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Parasound A21 In Mono vs. Parasound JC1's

So...
I've searched the Audiogon discussion forum and countless other places on the web for the Parasound A21 In mono mode vs. Parasound JC1's comparison.

For it is my understanding the A21 in mono pushes out 700 watts (at an 8ohm load) in mono which is over a hundred watts more than a single JC1 (I'm aware the JC1's are rated at 400 watts...however, I discovered a third party company did ran a test, and the JC1's pushed out 586 watts before clipping).

With this in mind, what is the true benefit of purchasing the JC1's (for one could save 4 grand and buy 2 A21's and get more output)?
Would the wattage in Class A mode be much more substantial with the JC1's?

Would the difference, in essence, be a few minor nuances for only those people with "trained ears" to hear (to which at this point IMHO these type of listeners aren't enjoying the music but rather studying the music and the equipment to hear things they claim they haven't before.  This is a subject in itself for the brain can "literally" only focus on 1 task at a time (a proven fact to researchers in an article published a few years ago).  
How does that apply to what I'm saying: One can only focus on the low's and not the mids and/or highs at the same time.  Anyone in this disbelief is merely delusional and attempting to feel their ears and mind are supreme to anyone else).

My apologizes on losing focus to the subject that I'd like input on (but I felt it must be said so nobody goes off topic).
mdbag
auxinput
2,920 posts
 

A stereo amplifier that is run in "mono" mode will essentially double the pull on the power supply. You are, essentially, running this stereo amplifier in bridged mode. This means that each channel of the amplifier is only seeing half of the speaker impedance. So, if you are running a flat 8 ohm speaker, each channel would be seeing a load of 4 ohms. That is why the power seems to double. At this point, you will have to be very careful on what speaker you choose to drive. Many speakers that are rated at 8 ohms will actually have an impedance curve that may drop down to as low as 3 ohms in certain bass / midbass frequencies. This means the each channel of the A21 running in bridged/mono mode will see only 1.5 ohms. This can put undue stress on the power supply and may cause heat/overload scenarios. The sound quality here may suffer a little as the power supply may not be as beefy as you need. Also, you may force the voltage rails that power the output circuit to running higher than they really are designed for. This specific fact is why is it never wise to run an amplifier in "bridge/mono" mode unless it was specifically designed for that.

It’s much better to run a true monoblock where the power supply rails and output circuits were designed to see a specifically lower impedance on the speaker output section.

auxinput
2,920 posts
 

That being said, the A21 has a 1.2 kVA transformer with 100,000uf capacitance in the power supply. 

The JC1 has a 1.9 kVA transformer with 132,000uf capacitance in the power supply.  This give the JC1 significantly more brute force in the power supply.

erik_squires
16,041 posts
 
Hi MDBag,

I'm a big fan of Parasound amps. I really think you should rely on your ears and not the technology per se. All their amps are pretty solid, quiet, smooth modern sounding amplifiers.

A true monoblock usually has better low-impedance tolerance (maybe 1-2 Ohms) while a stereo amp when bridged will limit this to 4 or even 8 Ohms. See the spec sheets.

The issue with a "bridged" amplifier however is not how you imagine it. :) The maximum voltage doubles but the max power quadruples.

However, to reach equal volume (loudness) the power used is the same no matter how an amp is configured.

Personally I used to run a pair of A23's to handle 4 of my 5.1 channels. :) One amp was L and L Surround, the other R and right surround. For music I essentially had monoblocks, with the power supply nearly dedicated to 1 channel, and no crosstalk. It was a neat set up.

Eventually I went to an all Class D monoblocks. My speakers are 8 Ohm and easy to drive, so it is an easy choice for me.

Best,

E
erik_squires
16,041 posts
 
I meant to say, in terms of impedance handling, the ranking (usually) goes like this:

Lowest (best): Monoblocks (Maybe 1 Ohm or so)
Middle : Stereo amplifier working as a stereo amp (2 - 4 Ohms minimum)
Highest impedance requirement (worst) : Bridged stereo amp. (sometimes requires 8 Ohms)

No hard and fast rules. But since bridged stereo amps have 2x the voltage, the theoretical output power is 4x normal. This is often unsubstainable at the lowest impedances.

Best,

E
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