Another wattage question.

bombaywalla: thank you for taking time to answer my question. Much clearer now. I always wondered about dynamic headroom spec but was afraid to ask. My "new" amp, an older Audio Research D-100, weighs twice as much as my old Hafler. Can I assume that it can handle these surges in power requirement more easily than the Hafler(48lbs compared to 24 lbs). Audio Research doesn't publish specs at 4 ohms? Or is that assumption invalid too?

Bottomsup,

IN GENERAL, I don't think that this assumption is valid. OTOH, ARC is a company with a long-standing reputation for good/excellent products. I have no personal experience w/ the D-100 so I cannot comment.

Nelson Pass once wrote an article on power supplies for power amps (It's on his website called "Power Supplies: Commentary for Consumers". Worth reading, IMHO). What he says there is that a toroidal xformer yields 30W/lb. From his paper I interpret that a 100W amp should be able to deliver 300W & that will force it to have a 900VA xformer, if the power supply is to be constructed correctly. Thus, this 900VA xformer will weigh 30lbs itself. Add heat-sinking, power supply caps, electronics, damping material & one could easily double the weight to 60lbs.
If a 100W amp can deliver 300W, it has atleast 3dB dynamic headroom.
Going by this white paper, 48lbs is on the low side. However, white papers are white papers! The proof of the pudding lies in listening to the amp. I doubt that the amp doubles its wattage as speaker imp. halves but that doesn't mean it's a bad amp! Listen to it, put it thru the ringer & you'll answer your question.

Bombaywalla, thanks, your reply above is one of the rare and priceless explanations that help people to get smarter in their audio quest... If there were Audiogon FAQ, this reply definitelly should be there.

Thanks professor Bombaywalla !!!

Bombaywalla,

Thanks very much for your informative posts!! I second Dmitrydr, this should be in a FAQ. Are you an engineer by any chance?