Reminder: how to tell current from an amp's specs?

I may be completely wrong, but I've been under the impression that an amp was considered "high current" if it was able to double (or nearly so) it's output wattage every time the load resistance was halved. So, 50W into 8ohms, 100W into 4ohms, 200W into 2ohms. Many amps won't do this, some will.

Thanks to everyone! And @atmasphere , I wrote my response before seeing that you had posted your very helpful response. I think I'm getting it!

Ohm’s law alone does not apply to power. If you put a 4-ohm resistor across a 9-volt battery, does that mean the resistor is consuming (9*9/4) 20 watts? No. That would mean the battery would have to accommodate the resistor with slightly more than 2 amps, but it the most it can do about half an amp. So the answer is a high current amplifier is one where it stores enough energy to maintain voltage over the speaker’s varying impedance.

You cannot tell from the specs how much energy it stores because most of the manufacturers specify the power at only one impedance (an 8-ohm resistive load). A speaker presents an inductive load which varies with frequency. But you can get an indication of the performance if the manufacturer provides power ratings at less than 8-ohms. Levinson, Krell and the like maintain their voltage (energy) down to two ohms. If an amp can do that at a 1-ohm load, then it’s truly a high current amplifier. Literally.

Here is another well-written article on this topic:

http://education.lenardaudio.com/en/14_valve_amps_7.html

@builder3

You are not wrong, but this general quick reference rule of thumb is a good quick guide , but is not not an absolute bible .

Sure …. In many cases, you can recognize an amplifier with ample current delivery by looking at its wattage output as impedance decreases. A great amplifier will double down, so 100 watts at 8 ohms becomes 200 at 4 ohms.

BUT ….and its a BIG “but” … There are exceptions to this general “rule of thumb” quick reference guide.

The REGA Osiris integrated amp is one of these exceptions. While it is a beefy hi-current and high WPC amp that doesn’t fully double down, it still has LOTS of current because of its high-end build and design. This is provided by those four Sanken output transistors per channel, that insure that no speaker is too hard to drive.