CLASS A AMPLIFIERS

Unsound,

The Krell FPB "Class A" series maintain Class A operation
from 8 ohms to 2 ohms.

They have well regulated power supplies that have the current
capacity to deliver the current that low load impedances
require.

Given the well regulated nature of the power supply [i.e.
the ability to put out the rated voltage independent of load ]
and the current capacity to back it up - that's WHY a
Class A Krell will double down.

Dr. Gregory Greenman
Physicist

Unsound,

You can also check out the reviews by Stereophile, such as
Martin Collums April 1997 review of the then current FPB-600.

http://stereophile.com/amplificationreviews/829/

In the Measurements segment, Martin addresses the power that
the amp can deliver into low impedances:

http://stereophile.com/amplificationreviews/829/index8.html

"I wasn't able to run my long-term continuous testing at
2 ohms, but compromised with five-second bursts-long by
peak-measurement practice (eg, 20ms). The FPB 600 could
sustain a 29.3dBW level into this load, corresponding to
3.4kWpc-an extraordinary figure."

Dr. Gregory Greenman
Physicist

Unless I missed something, everything in these aritcles suggest that the Krell's are capable of maintaining Class A operation as they double down, but, they don't actually make that claim. As for me, I believe they do. Wretched excess? I love it! I may be part of the minority here on Audiogon, but I really like the "real" Krells and thats based on what I've heard not on what I've read. Though it is pretty impressive reading.

Unsound,

The circuit topology of the Krell FPB series is Class A.

Class A amps don't automatically resort to A/B when they
are asked to output large amounts of power.

No - that is a characteristic of Class A/B amps that are
designed to maintain Class A at low levels - and then they
revert to what they really are Class A/B.

However, a true Class A like the Krells doesn't automatically
revert to A/B at high levels.

Dr. Gregory Greenman
Physicist

Moribus, thank you. That really clarifies it. Am I correct in assuming that power increases by ss amps into lower impedances is not determined by Class of operation?