CLASS A AMPLIFIERS

Unsound, I remember having a conversation with Jon Soderberg, formerly with Threshold and now a top repairman for the older amps. He told me that on the SA-1 that I was actively pursuing that it would double in power into 4 ohms but that the Class A amount of it would be cut in half. Whatever the Class A power was into my Apogees, it was really sweet.

Unsound

Here is the exact information fronm the pas web site I quoted.

"The XA-200 will deliver 200 watts rms into 8
ohms of impedance. This is the amplifiers class
A limit, driving the XA-200 harder or reducing the
impedance of the load will not convey any additional
power. Driving into a short will not convey any
additional power. These are not design oversights or
flaws in the XA-200, but rather a condition of the
very highly biased Class A operation. However, as
an interesting point of reference, 200 watts driving
a 87dB/1W/1m speaker will deliver a 112 dB (very
loud) average acoustic signal in a 100 cubic meter
room. Transient peaks will be somewhat higher."

Chuck

Chuck, thanks. It's interesting that Pass suggests that "These are not design oversights or flaws in the XA-200, but rather a condition of the very highly biased Class A operation." I don't recall this "reasoning" from some other Class A amplifier manufacturers. It may even contradict what is commonly percieved as techincally available from Pass' previous designs.

Onemug, Jon recently told me the same thing re: a different Class A/AB Threshold amp.

highly biased Class A operation

This is probably Mr Pass' way of saying the device is operating in "deep class A". Just the PS is well over the expected 4x the energy output rating fro class A.