First Watt: current vs voltage

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Liguy and Bombay, you are incorrect. There is a night and day difference in the way current and voltage source amps operate. They are not just power amps.

Some of the First Watt are current source amps and some are the more common voltage source amps. I think Mr. Pass screwed up to mix the two topologies in one line of amps since it leads to confusion like this.

The current source models will not work with most speakers. They are not the equivalent of SET tube amps as the latter are voltage source amps. The need to use them with single drivers has no relationship to the fact that most of these speakers are efficient even though being lower power does make a good match with them.

From the F1 manual

"This is a very unusual amplifier that will not sound good with about 98% of the loudspeakers on the market. It requires careful attention to loudspeaker loading to get the best performance.

It does not work well with ordinary passive crossover networks – the components and their locations tend to be reversed. It won’t break, but probably won’t sound good."

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Stan, sort of.

For a given input voltage an ideal voltage source will maintain a constant output voltage no matter what the load i.e. no matter how low the load impedance goes and no matter how much current the load draws. This requires the amp to have extremely low output impedance, ideally zero. Monstrous power amps like Krells are closer to these ideals than the Quad but they are both considered voltage sources.

Current sources are an entirely different beast.

For a given input voltage an ideal current source will maintain a constant output current no matter what the load. This requires the amp to have extremely high output impedance, ideally infinite. The First Watts are not that high with an output impedance around 80 ohms but that is 10 times most loads so they act more like current sources.

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