Current output...

I think I may be getting it..?? (well something anyway). I have been living happily with the 3w ECL86 amp (current output reigned in by feedback) for some months, and am accustomed to its sound now. A friend has recently returned my Class A hybrid digital amp and I thought I would try it out again. I instantly noticed a sort of grungy ness and colder “transistory” sound, even though this is a no feedback design with a transistor emitter follower output. It is curious how the little IB two way speakers don’t like transistor amps.

I got to thinking about current output amplifiers, I was intrigued a few months ago by some comments on an article in the EE times Consumer audio: Is accurate sound overrated? where the poster "Cookie Jar"  stated “One day on a whim, I hooked up my distortion meters to the actual speaker terminals of my living room stereo, and I was in for a rude awakening. The distortion readings were a couple of orders higher than for a pure resistor load! “.

Yesterday I was doing a work related investigation in to current output amplifiers, and I bumped in to the interesting Current-Drive - The Natural Way of Loudspeaker Operation website, it states amongst other things, in reference to voltage output amplifiers “Many of these effects also manifest themselves as clearly observable harmonic or modulation distortion mainly as a consequence of the corrupted voltage/current conversion occurring in the driver.” I do wonder if this is the effect I have just been hearing.

So my perpetually evolving Hybrid amp project now consists of a pentode and a solid state current output stage... today.

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