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Original Message

RE: Broskie is correct on this one.

Posted by AmadeusMozart on June 16, 2021 at 14:57:00:
I am very fond of a floating paraphase inverter that is adjustable. Rather than making the "perfect" inverter with a "perfect balanced output".

The advantages of the adjustable floating paraphase inverter is that you can adjust symetry with output tubes that have either more or less different amplification factors.

I measured this when I built an Audio Note clone that had a floating parapahese inverter followed by a6SN7 before driving the output tubes.

when the inverter was adjusted for "perfect symmetry" the end result with "perfect (within 1%) matched 6SN7 followed by "perfect matched" output tubes was more than twice as large as when I simply adjusted the inverter for best output.

When using less than perfect matched 6SN7's or output tubes the difference became larger although a hefty dosis of negative feedback attempts to correct this. But then IMD started to shoot up (the result of GNFB).

The moral of this post? Start viewing a design in its totality rather than splitting a design up and ending up with a worse result.

AM