2. amps-preamps
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Amp Designs That Are Able To Drive 4/2 Ohms Load

I have noticed that some amps like the Krell Evo 302 will output the exact wattage when halving the impedances ie. 300W/600W/1200W into 8/4/2 ohms respectively. On the other hand, some amps like the Bryston 7B-SST does not output the exact wattage when halving the impedances ie. 600W/8 ohms to 900W/4 ohms or the Plinius SA-100 (100W/8 ohms to 180W/4 ohms)

Can someone enlighten as to where the 'missing' watts have gone for amps that do not output the exact 2X the wattage when going from an 8 ohm to 4 ohm load? What are the criterias in amp design that determine which route to adopt, and what are the pros and cons of each design?

Thanks in advance.
ryder
dave_b's avatar
dave_b
3,159 posts
 
Sorry, but designing for compromise is crappy design...period! I've found Krell for example sounds best driving a difficult load. Also, class A (at least in the pre-driver stage) is more musical. Case in point, the new Evo amps (no longer class A), which I owned for a time, sounded cold and flat compared to even the 400xi integrated. One must have an ear for exquisite tonal colors however...otherwise Bose will do just fine! Of course not everyone will agree, but i'll take a "Quantum of Solace" in the knowledge that JValin and Martin Colloms might just agree with me.
atmasphere's avatar
atmasphere
11,793 posts
 
Ryder, take a look at
http://www.atma-sphere.com/papers/paradigm_paper2.html

In a nutshell, 'Doubling power' as the impedance is cut in half says nothing about how the amp sounds, in fact there is nothing in the rules of human hearing to suggest that this is helpful.

The result is, there are amplifiers that don't/can't double power as impedance is halved that nevertheless sound better than many amps that can double power, because the former are designed to the rules of human hearing.
unsound
7,329 posts
 
I suppose they're are two schools of thought. One that believes that amps should drive speakers and one that believes speakers should accomodate amps. I'm (currently) from the former. No matter how challenging, we have amps that can successfully drive lower impedance speakers. Simply put, in my experience, systems with lower impedance speakers tend to sound better than systems with higher impedance speakers. Of course, YMMV, amplify accordingly.
dave_b's avatar
dave_b
3,159 posts
 
Ah, the elusive art of design...there still be magic unknown to mere mortals and engineers. Owning alot of systems over the years has afforded me first hand knowledge, not just a theoretical perspective. Even the tube gear I've owned used class A circuitry...none better nor sweeter for the human ear!
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