Negative Feedback Loops and the Fender Presence Control

This video provides a basic discussion of the design and function of Negative Feedback Loops and the early (and enigmatic) Fender Presence Control. It also explains how to convert your amplifier to Variable Negative Feedback.

Here is a link to a previous video, in which the audible changes in tone resulting from adjustment of the NFB are demonstrated:    • Scratch Building a Fender 5F1 Champ f...   NOTE: The audio portion begins at 14 Minutes into the video.

NOTE: To turn the NFB Loop into a Resonance or Depth Control, add a .0047uf capacitor in series with the NFB resistor. To make it variable, add a 1Meg pot in parallel with the capacitor with one leg of cap. connected to the center (wiper) lug of the pot and the other leg connected to either of the (outer) lugs of the pot. For this to function, the Presence Control (if you had one) would have to be "off" so no high frequencies were being sent to ground.

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