Pass is the founder and CEO of Pass Laboratories, but I first met him in the late
1970s when he was still with his first company, Threshold.
Even then he was known for his amplifier designs, but he was hard at work
developing an experimental speaker with a seemingly impossible design goal: no
moving/vibrating parts! He dubbed it the "Ion Cloud" speaker, which ran very high
voltages through tungsten filaments (of the sort used in photocopy machines) to
ionize the air to produce sound. Right, zero commercial potential, but it worked! The
Ion Cloud looked like a screen door and its sound wowed the crowds at the
Consumer Electronics Show.
Pass next went to work perfecting amplifiers with
"simple circuits," because as he once so
eloquently put it, "complexity tends to be the
nemesis of musicality." As he refines a design,
he listens to how individual parts
—capacitors,
resistors, semiconductors, etc.
—change not only
what he can measure, but they also put their
"signatures" on the sound.
So with these simple circuit designs there's a
strong correlation between what Pass measures
and what he hears. And he listens a lot. If
anybody can distinguish between the sound of
an amp from the speaker it's driving, it's Nelson Pass.
The Pass Labs INT-30A is a 30-watt-per-channel, stereo integrated amplifier, but it
sounds a lot more powerful than any 30-watt amp I've ever used.
The power rating refers to the amp's output while operating in Class A mode, into 8
ohm loads, and doubles to 60 watts into 4 ohms. Not only that, the INT-30A can
easily deliver 100 watts on peaks, but only the first 30 watts will be Class A watts.
The amplifier is 19 inches wide, 7 high, 19 deep and it weighs a hefty 60 pounds.
Along with simple circuits Pass believes that Class A circuits are essential if the goal
is to produce the best sound. So if it's such a nifty idea, why aren't all amplifiers Class