what about NFB on speaker jack??

[antosimoni]

how does it affect sound on '68 clones putting 47k NFB on speaker jack ??? it will have more or less gain than 47k NFB on 8 ohm tap ???
thanks a lot

[89custom]

It depends on the impedance setting...at 8 ohms, it will be the same, at 16 ohms, it will have more negative feedback, and at 4 ohms, less negative feedback.

[Tone-Freak]

so does that mean that if the NFB wire is connected to the speaker jack it will sound the same no matter what you have the impedence on? And if it is connected to the 8 ohm tap it will be cleaner if you have your amp set to 16 ohm and if set to 8 is the same as having it on the speaker jack? and 4 ohm setting will be dirtier (less NFB) ?Thanks

[paulster]

so does that mean that if the NFB wire is connected to the speaker jack it will sound the same no matter what you have the impedence on? And if it is connected to the 8 ohm tap it will be cleaner if you have your amp set to 16 ohm and if set to 8 is the same as having it on the speaker jack? and 4 ohm setting will be dirtier (less NFB) ?Thanks

No, if you have it connected to the impedance selector it will sound the same no matter what impedance you are on.

If you have it connected to the speaker jack then the level of NFB will be altered by the position of the impedance selector, so if you ran a full stack rather than a half-stack (for example) one day you'd be at half the impedance and therefore 0.7 times the voltage you had on the higher tap, which means you'll have correspondingly less negative feedback being applied.

Put it on the impedance selector on whatever tap best to you (all it does is alter the amount of NFB applied) and it'll retain the equivalent amount of NFB regardless of the switch position of the impedance of the cab connected.

Basically, Marshall did it wrong on a lot of amps.