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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
erik_squires
15,657 posts
 
I don't think we are saying anything that much different, @atmasphere


Current feedback would raise the apparent output impedance into the range I was discussing, just like voltage feedback lowers the apparent output impedance.
itsjustme
681 posts
 
My answer to the original posed question is "not at all, not even close"

I think Eric contributed some good stuff above.


As am amp designer, i think they ought to be voltage sources, with low output impedance.  Now, for the record mine are not zero, because i don't like to employ global control (feedback) loops nor expose those loops to external elements that create unknown stability issues.  But we are talking small fractions of an ohm.

I realize that a higher output impedance may result in a warmer 'bloom", but that's a coloration, whether you like it or not.


A current source would likely result in very distorted sound. Also note that the impedance of a speaker changes on many dimensions - with frequency, with excursion of the electromagnets, with volume, ....so why would we want to make the gain impedance dependent?
G
erik_squires
15,657 posts
 
Well, I was talking in engineering and mathematical generalities.

What is ideal is very different than what we would like to hear.  If you ask me what the best amplifier I ever heard was it was probably the CJ Premiere 12.  If only I had the space and money for them. :)

Best,

Erik
itsjustme
681 posts
 
Erik-just for clarity - I was not disagreeing with you, just adding and referencing what you said rather than blather on and being repetitive :-)

jtgofish
490 posts
 
It would be very interesting to learn about the intricacies of the Bakoon amplifiers.They are reputed to be current drive and have high output impedance and yet seem to be able to drive many mainstream speakers without problems although they definitely sound best with genuine 8 ohm speakers rather than 4 ohm.It is surprising what speakers even the base model 15 watt will drive and they sound superb.I have owned every type of amplifier other than an OTL and the Bakoon is by far the best sounding.There is just a fundamental rightness to the sound and that is hard to unhear.
It would be interesting to know exactly how the patented SATRI circuit  works but if that information is available it is probably in Japanese.
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