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In Reply to: RE: Efficiency and Sensitivity are not the same thing! posted by Ralph on May 08, 2017 at 10:49:19
One should also keep in mind that all amps regardless of technology have greater distortion into 4 ohms, and so will sound harsher and less detailed.
That may be true for direct-coupled amps (I can't think of any exceptions). But many transformer coupled amps have the same or higher distortion from their 8 ohm taps into an 8 ohm load than from their 4 ohm taps into a 4 ohm load, at equal power. And it's not just some tube amps, the McIntosh solid state amps exhibit this behavior too.
Just by using the 4 ohm tap instead of the 8 ohm tap (and assuming that in each case the taps are loaded correctly) with some output transformers. I forgot to mention that...
What would be the mechanism for that?
Certainly connecting a 8 ohms load to the 4 ohms tap will cause the LF -3db point to move one octave up because the reflected impedance has doubled but the inductance stayed the same but the reflected impedance with a 4ohm load connected to the 4 ohm tap should be the same as a 8 ohm load connected to the 8 ohms tap and therefore the LF -3db point should stay the same.
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therefore the LF -3db point should stay the same.
Emphasis added; 'should' being the modifier in that sentence, and I agree.
However, in reality the fact is that the larger the turns ratio it seems that there is a loss of efficiency. We've had several custom transformer projects and run into this phenomena. I suspect a YMMV thing depending on the quality of the part.
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