Ps Audio BHK Signature vs Parasound Halo A 21+

MOSFET amplifiers can be very capable of providing adequate current.  The Audio by Van Alstine FET Valve 600R I have drives my Magneplanar 3.7i's very well.  Certainly as well as my Parasound Halo A21 from the listening perspective.  According to its specifications, the BHK doubles its 8 ohm output into 4 ohms.  Don't know how that can be done without increasing current commensurately.  But I'm certainly willing to be educated.  

There is more to amplifier design that the kind of output transistor used

Read everything, that why this is said at the end.

  So to me it comes down to what speaker you have, and if they are easy load and suits both amps, then try to listen to both on your speakers, and pick the one that sounds better.

altchavez OP
Thanks , my speakers are a pair of Dynaudio Contour 20

These shouldn’t be a problem not too hard to drive with either Bi-Polar or Mosfet amps even Class-D or Tube, in either reflex (ported) or infinite-baffle modes
https://www.stereophile.com/images/417DC20fig1.jpg

https://www.stereophile.com/images/417DC20fig2.jpg

Though there is a combination of 5.2 ohms and –38° capacitive phase angle at 120Hz, the Contour 20 will work well with tube amplifiers, as Herb found.

Cheers George

Your question is impossible for any of us to answer reasonably. The better amp is the one that sounds better to YOU, with your system in your room. None of us can predict that.

There is more to amplifier design that the kind of output transistor used and the choice is up to the designer.  And not all speakers are in the same difficult to drive category as Wilsons.  Hell my old JVC boom box uses bipolars   but it doesn't compare to my Pass amp.
 

Damn it George, Last October I upgraded from my old dspa1 to outlaw mono amps with an older outlaw processor, then couple months bought the 60xt and have been pretty happy.  Lately though I've been wondering if the 60xt can sound even better than they do with better amps. I'm glad my s.o. doesn't read these forums. The halo 21+ has me wondering. 

Thanks , my speakers are a pair of Dynaudio Contour 20

altchavez

From a design point both are good amps, the BHK uses Mosfet output where the A21+ uses Bi-Polar.
All the great amps that have "reputation" for driving impedance’s down to 2ohm or less comfortably with great current ability, have been mostly Bi-Polar output amps.
So it really comes down to what speaker you are using.

EG: Say your using a ML Motion 60xt that I commented on a couple of days ago, they would prefer the Halo A21+ Bi-Polar amp, as these speaker are quite a constant 2ohm load with 63 degrees of -phase angle in the bass, where all the current is needed.
https://www.stereo.net.au/forums/uploads/monthly_2017_02/martin.jpg.65381e35cdfe44b6833f3002affd5da7.jpg

So to me it comes down to what speaker you have, and if they are easy load and suits both amps, then try to listen to both on your speakers, and pick the one that sounds better.

Cheers George