5e3 NFB mod. Position of SPDT switch?

[Halfdiminished]

About to start 5e3 and am planning to use Rob Robinette's NFB switch mod. The typical positions for the switch appear to be adjacent to the speaker jacks or in place of the extension speaker jack. I was wondering about putting it in place of the Normal Lo jack - is this position not used due to the proximity of input wiring and therefore risk of noise? Would shielded cable prevent this?

thanks

 

[misterdontmove]

About to start 5e3 and am planning to use Rob Robinette's NFB switch mod. The typical positions for the switch appear to be adjacent to the speaker jacks or in place of the extension speaker jack. I was wondering about putting it in place of the Normal Lo jack - is this position not used due to the proximity of input wiring and therefore risk of noise? Would shielded cable prevent this?

thanks

It's probably placed there do to proximity of the output jack where the negative feedback is supplied. The 3 positions, especially the NFB position, require some volume and tone tweaking, so it's unlikely you'll switch it "on the fly". On blackface amps the negative feedback resistor is located on the board, quite a distance from the output jack, and I don't think they used shielded cable. I may be wrong (I often am). Have fun with it.

 

[Powdog]

I’ve put an adjustable NFB pot in one of the input jack holes before with no problems. I also install a “Voice” switch into the “Ground” hole on a 5E3 chassis which places it farther from the sensitive preamp side. The NFB signal is pretty low level. Either location is fine.

 

[Peegoo]

Noise is not an issue with this.

On my Champs I installed a little toggle switch on the bottom of the chassis, pointing downward. Looking at the back of the amp, it looks totally stock.

The toggle rocks front to back to make use of the switch intuitive: NFB loop "in," and "out."

 

[Les Gear]