Are all amps being built wrong?

Bob Carver made amps under the Sunfire brand that had speaker outputs selectable for voltage or current drive. I’m told the current drive was created by the insertion of a series resistor. 

Both my sugden and marantz sound great....so No...

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**As we all know our speakers suffer from very low sensitivity,,,and the music consequently is only heard in bits and pieces,,,we need alot lot more power to drive our Wilson's, Vandersteens, Thiels,. Tektonics, Magnepans**

BS…
My 100W SS and then the 100W tunes powered my Vandersteens fine.Or maybe nit the PSE died 16 years in, and the VTLs 15 years later, and the latest one and a NAD before that worked fine.
I would not trade them except for a 36 year new version. And even then maybe not.
But the OP has a point about current.
Speakers with a more uniform impedance, would get a more uniform current at a fixed voltage. Maybe there is something in it?Or
We fix wild impedance swings with a current source amp? 

When I was doing some research, I came across a comment in one of the Coda related Audiogon threads that states Coda makes the Sanders Magtech amp; but, Sanders than tweaks it for use on their ESL speakers.

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 mostly incorrect.


The voltage rules haven't been around forever; MacIntosh and EV were proponents of this in the late 1950s but it took until the 1970s before the industry had really switched over from the older power rules. The idea was plug and play with no adjustments on the loudspeaker. You can read more about it at this link:
http://www.atma-sphere.com/en/resources-paradigms-in-amplifier-design.html
Any time you see adjustments on the back of the speaker like a tweeter level control, the speaker is designed around the older power rules- the control(s) allow the speaker to be adjusted to the voltage response of the amplifier and are not there to adjust to the room.

Of course a current source amp would be even more sensitive to impedance variation than even a power source amp! But there are speakers that worked best this way; most of them are open baffle with very tight suspensions on the drivers.


The problem for many years with the voltage rules has been the to get the amp to be a voltage sources (especially tube amps) you need feedback, and the simple fact has been that most amps made in the last 70 years that have employed it simply do not have enough. As a result the feedback that they do have has caused all of them tube or solid state to be brighter than they should be, since the feedback wasn't enough to allow the amp to clean up the distortion added by the feedback itself.


Since the ear perceives distortion as tonality, and since the distortion added by feedback (while suppressing the innate distortion of the amp otherwise) is entirely higher ordered harmonics, the ear perceives that as brighter and harsher even though the amp might be flatter frequency response.


That is why there are still power source amps around today (SETs being an example). Tube amps that don't use feedback (and so are not as harsh and bright) will act like a power source.


The trick with feedback of course is to have enough, which is usually over about 35dB or else don't use any at all. Its not really been possible to put that kind of feedback in an amplifier until recently. The typical brightness of solid state (which is why tubes are still being made) is caused by insufficient feedback.