There is interesting recent (? 2011..2013 ?) claim about superiority of current driven audio amplifiers. I agree with author, except one fundamental flaw in relevance to practically available audio records. None of contemporary records will reproduce correctly with his amplifier. Also voltage driven amplifiers will try to reproduce correctly, but will also fail for the reasons explained by author in EDN article.


I think there is one small block is missing to complete perfect current driven amplifier: it is differentiator.


To verify my thoughts, I checked the current basics of acoustic theory. After reading this paper (up to p 2-14), it is correct to say that microphone voltage corresponds to instantaneous value of acoustic pressure, because particle velocity (velocity of weightless membrane) is in phase with momentary pressure. This means that all audio records are records of pressure.

".. It is noteworthy that for a plane wave, the particle velocity and the particle displacement

are 90 degrees out of phase, but that the velocity and acoustic pressure are in phase. .."


To perfectly reproduce the pressure back from recorded voltage data through ordinary speakers, the velocity of speakers should match. Author (Esa Merilainen) with his approach interprets voltage data as a torque: mechanical force applied by speaker, causing match of acceleration (very good match, better than match of voltage amplifier to velocity), but in actuality the need is in reproduction of velocity to match the acoustic pressure.


My claim is: none of voltage or current amplifiers will sound correctly (mostly phase wise) when are driven by unmodified voltage records. To perfectly match the acoustic pressure recorded by microphones the current amplifier needs a differentiator.