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
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