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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

Showing 2 responses by ryder

ryder OP
1,742 posts
 
My one tube amp is stable at 2 ohms, but the same wattage output as 8 ohms. My other mono block tubes are stable to 1.4 ohms but put out the same wattage as they do at 16 ohms or 70 volts.

Pardon my ignorance. How do you know your tube amp is stable at 2 ohms? Is the amp capable of driving speakers at 2 ohm load or did the spec specify this? I am just curious on the differences in the output wattages for various amp manufacturers when the impedance is halved. As others have pointed out, the power supply is the critical factor in determining the power output. Now I'm more confused to hear of tube amps that will output a similiar wattage at varying impedances.
ryder OP
1,742 posts
 
Gs5556, thanks for posting. That had clarified most of the doubts I had previously.
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