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
Ralph (Atmasphere) posted: 
If you add a resistor to the output of a solid state amp it will indeed simulate some sort of tube amp that uses feedback. Most transformer coupled tube amps with 15dB of feedback will act as a pretty good voltage source. You might have to play with the taps on the output transformer. Between Voltage source and Current source there is Power Source, which is how a tube amp will behave if it has no feedback or if it has voltage and current feedback of equal amounts.

I think Ralph is right on.  My ARC Ref 80S is a transformer coupled tube amp that uses 14db of negative feedback.  And I do **play** with the taps to get the best sound.  At this point, I have settled on the 8 ohm taps, which I believe have an output impedance of approximately 1 ohm.  The DF is 8 if the amp is coupled to an 8 ohm speaker off the 8 ohm taps.

As to comments made by others, I believe that it is correct to say that matching my amp (or one like it) to a speaker that was designed and voiced to be driven by a constant voltage source amp is a bit of a tone control.  To some extent the amp's voltage output will vary to some degree as a function of speaker impedance, which in turn, will vary with frequency.  

All that said, I like the sound of my amp/speaker combo, ... tone control and all.  Ironically, I surmise that between room affects which probably boost the bass a bit and and the tone control affects of the amp which soften the tweeter/high frequencies, the overall frequency response and sound is musical and pleasant.  Just my opinion. 

BIF

I also did not measure their spectral output, just listened. using my favorite measurement aid of the time, single malt scotch.
vidmate  mobdro
If one was to use a DSP, then (I think that) all gets normalised to be right whether using a voltage or current source?


Room correction in modern systems would be doing the same thing I think.