ampage Tube Amps / Music Electronics	For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

NFB -- where its tapped, & NFB resistor

10/10/1999 8:09 PM
Dave M.	NFB -- where its tapped, & NFB resistor RE: same amp -- '73 Marshall 1987 I've seen a few schematics for the 1987, and among them I've seen the NFB loop coming from the 4, 8, and 16 ohm tap. My praticular amp has it from the 4 ohm tap. I'm curious why this is, and what differences are heard? On a related note is the NFB resistor. Most of the schem's I've seen show a 47k. Of those, they also spec, in parantheses) a 100k. I'm assuming that the 100k was an option of some sort, but why? What differences would 100k vs. 47k do? What could you expect to hear overall? TIA again, -Dave M.

10/10/1999 8:09 PM

Dave M.

NFB -- where its tapped, & NFB resistor

RE: same amp -- '73 Marshall 1987

I've seen a few schematics for the 1987, and among them I've seen the NFB loop coming from the 4, 8, and 16 ohm tap. My praticular amp has it from the 4 ohm tap. I'm curious why this is, and what differences are heard?

On a related note is the NFB resistor. Most of the schem's I've seen show a 47k. Of those, they also spec, in parantheses) a 100k. I'm assuming that the 100k was an option of some sort, but why? What differences would 100k vs. 47k do? What could you expect to hear overall?

TIA again,
-Dave M.

Replies:

SpeedRacer 47k is the value for the 50W heads,... -- 10/10/1999 8:15 PM