For Sluckey - question on Mark Huss's 6V6 Plexi schematic

[ac427v]

"change the resistor, higher more FB, lower less" seems backwards to me. How does this work?Craig B

[dude]

http://www.aikenamps.com/index.php/designing-for-global-negative-feedback

[PRR]

> "change the resistor, higher more FB, lower less" seems backwards to me.

I think the thought is run-together.

I think he means: change the TAP, 4/8/16, to a higher number, same resistor value, makes more NFB.

You can instead change the resistor, and there's two involved (though the lower one may also be biasing something).

[dude]

> "change the resistor, higher more FB, lower less" seems backwards to me. I think he means: change the TAP, 4/8/16, to a higher number, same resistor value, makes more NFB

Yes, the negative feedback cuts natural distortion, makes the amp sound cleaner, tighter, maybe a good thing but for me it cuts the slower progression into distortion that you get with less negative feedback, too much NFB can cause the amp to sound sterile, more high fi sounding. For me feedback R around 22K to 27K on the 8 or 4 ohms tap is plenty, the amp distorts with a longer curve and more natural, not just going from clean to distortion. The article says the ratio to the R value to ground and the feedback R, creates the feedback, I assumed the 5K pot is a variable R to ground.


I wasn't getting the full effect of the tone stack due to too much NFB, too clean and slightly sterile to my ears. Anyway, lowering the feedback R from the 16 ohm tap to the 4 ohm tap, took out some of the feedback.