Are all amps being built wrong?


The power amplifiers that drive our loudspeakers are mostly built as a low impedance voltage source. They have always been ... but why?

Loudspeakers have a (greatly) varying impedance over the frequency range. A current drive amplifier would eliminate the issues that stem from this varying impedance, and at the same time make discussions about esoteric speaker cables that strive for optimal R, C, L superfluous. Although there still would be these un-measurable ’this (very expensive) cable sounds better’ debates and opinions ... and that’s OK, that’s part of the fun. :)

So ... why are amplifiers not built as a high impedance current source?

This is an interesting read: https://www.current-drive.info/
rudyb
Julius Futterman solved the tube amp feedback problem by eliminating the output transformer. His OTL amps can have 60 db feedback with low output impedance and low harmonic/IM distortion. Yet remain 100% stabile into complex loads! The drawback is that they are best used with speakers that are 8 ohms and up due to the fact that power/watts declines into low impedances - but rises with impedance increase!
The solution is to add an autoformer to the Futterman OTL's output. Say, 16 to 32 ohms. This will allow low impedance drive. And a corresponding increase in power/watts from 60 to 120 to 240 from a sextet of 6LF6 output tubes! 
I have three Futterman OTL's. Two mono's and a stereo chassis version that Julius made and sold as the Harvard Music H3 in the mid-Sixties. That one got a review in the old High Fidelity mag! The H3 I bought has an added pair of Altec autoformers because the first owner used it to drive a large custom-made pair of panel speakers that had ten oval cone drivers per side! Consequently these presented a low impedance that the stock H3 couldn't drive - hence the Altec autoformers!
There is a purity and transparency of the sound of the Futterman's that must be heard to be believed! I first heard a friend's pair driving Quad 57's back in 1978 and was instantly convinced that the Futterman OTL's are world-beater amps!