Class A Amplifiers and impedance dips

Gs,
Not only the power supply but output transistors also have a characteristics to react on different loads as well as delivered current limitations.

ALL amplifiers, even cheapo AB's, have more power to throw at lower impedance. Super cheap receivers, ie sony, won't work with even a 4 ohm load. The best way to explain it is it works like the output of a pump. The pump is the power supply. As you lower impedance, you make the outflow pipe bigger, and the pump gets water out more easily. The better pumps can handle pumping more water- cheaper pumps start to burn up. Really good s.s. amps can handle 1 ohm loads. Certain "8 ohm" speakers can dip down that low. Tube amps do not like low impedance, which is why you have to be careful and buy a speaker with a stable load. In the bad old days friends sold the carver "amazing loudspeaker" with impedance dips so low that it fried most amps.

Mitch4t,

As Gs5556 and Marakanetz have pointed out; the amplifier
class has nothing to do with whether the amp doubles its
power as the impedance is halved.

The doubling is a function of what the power supply and
output stage are capable of. You can have a Class A amp
that does not double - and you can have a Class A/B amp
that does double.

However, you may still see more Class A amps that double
than Class A/B. It's not a function of the amplifier
Class - but due to the fact that a manufacturer that takes
the philosophy of going Class A - accepting the down-side
of extra heat generation, etc in order to gain the
advantages of a Class A - might also provide the beefier
power supply and output stages needed to power double.

Class A and power doubling are not "cause and effect" - but
rather are both hallmarks of a design philosophy.

Dr. Gregory Greenman
Physicist

I love this website!!! ....What a reservoir of knowledge and help.

Thanks guys for your help.

mitch

Is there an agency that dictates what class A or other designation actually consists of? How does one know if a manufacturer claims class A for their amp that it really is and does any agency ever check? I am not doubting any information here just would much prefer to read an authoritive white paper if someone can point us.

Thanks,