Voltage source vs. current source amplifiers


I’ve been reading a little bit about the different amplifier designs and understand that some power amplifiers operate as a voltage source whereas others are considered current sources. In broad sense, it appears that the amplifiers that increase their power as the load impedance drops - ideally double as the load halves, are voltage sources and the ones that maintain the same power, or close to it, regardless of the load impedance are current sources. Going by the specs, it looks like almost all the tube amplifiers fall in the current source category. I’ve also read that most ESL design speakers such as Martin Logan generally act as a capacitor so a voltage source amplifier would be a better choice. In contrast, magnetic/ribbon design speakers such as Magnepans are resistive so a current source amplifier would be a better option. I guess dynamic speakers fall somewhere in between. Looking in the market, it looks like McIntoch is one of the (very) few companies that is making a current source non-tube amplifier. I’m wondering why a lot of folks find McIntosh very nicely paired with ESLs like Martin Logans. Similarly, Magnepans should pair very well with tube amps.
Just wondering.
128x128kalali
I was a technician, not an engineer, but I do know that a tube is a voltage amplifier and a transistor is a current amplifier. The Martin Logans have powered woofers so tubes can handle the relatively easy load of the mid/treble panel. The Magnepans don’t have them so need a lot more current for the low frequencies.
Ideal voltage source provides voltage that is independent of the load.
Power delivered will be inversely proportional to load impedance.

Ideal current source provides current that is independent of the load.
Power delivered will be proportional to load impedance.

Only certain ML models have powered woofers - my Aerius doesn’t for example. But I agree kijanski has it right. The amp will need to double the power when the load is halved in order to maintain a constant voltage. In contrast, the tube amps almost always either maintain the power or in some cases even increase the power when the load is reduced. What prompted me to read up on this was my current set up where I have my McIntosh MC2200 - 200 wpc @ 8,4,2 ohms, driving my Aerius MLs and I have a Vincent - 150 wpc @ 8 and 300 wpc @ 4 ohms, driving my Def. Tech. BP10s. The "science" seems to suggest that I have to swap amps/speakers but the MLs sound better with the MC2200. I’m sure there are other factors in play but it was worth the experiment. Mainly wondering if others have found a correlation between the amp design and the type of speakers, etc.