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Re: Question on feedback and transformers

Posted by Ralph (M) on January 18, 2007 at 08:25:31

In Reply to: Re: Question on feedback and transformers posted by Tom Bavis on January 17, 2007 at 18:27:13:

Feedback introduces odd-ordered harmonics which the ear uses as loudness cues. Not good- the result is a sheen or hardness for which our ears have no need.

In order to be effective in lowering output impedance, a fair amount of gain is required within the feedback loop- more than is usually available from just the output section. This means that the feedback has to be global, which increases the time shift of the feedback, and increases odd orders.

Essentially there is no good way to do it. Keep in mind that the idea that tube amps ought to behave more like transistors is not good for your ears! In fact the story that a transistor amp's ability to double power as impedance is cut in half is a good thing is just that- a story (and most transistor amps rely heavily on feedback to accomplish this). Once free of that story, you get that the strength of tubes is their ability to operate much closer to the rules of human hearing. Take advantage of it- find a way to not use any feedback at all!

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