5E3 NFB switch in ground switch position?

[bonzerinc]

I'm building a Tweed Deluxe for someone who'd really like to have all the switches up top, but the ground switch spot is a really awkward fit for the NFB (RobRob's 3-way). Can I get away with it if I use shielded cable? Would all 3 leads need to be shielded? Or should I just give up on that location?


-Michael

[d95err]

I don’t see a problem there. I think it would work even with unshielded cable. NFB signal shouldn’t be that sensitive 

(Haven’t built that particular amp and type of NFB switch though)

[jordan86]

Does your chassis have two jacks for speaker out? You could ditch the second parallel jack and place a switch there. That’s what I did with my Princeton. Very easy placement since NFB lead is going to be running to the Jack anyway. Easy to reverse if you don’t like it.

You do have to be willing to give up that jack but there are lots of other cheap outboard options to parallel two cabs into one Jack. 

[shaun]

Heyo. I've done these Robinette mods. I found no great increase in noise, but then, I was after tone and not too fussy. And I got the creamiest tone I think I've ever heard.

Looking at the pic of the controls, I cascaded the two channels internally, so I installed the mini switch in the #1 input jack hole and moved the high input up to the #2 input hole (who uses the low input anyway? :). Now when I plug in to the Bright channel, I simply get the standard Bright channel as per original. If I plug into the new Gain channel, I get that channel cascaded through the Bright channel for big overdrive. I forget why it is switched; I think it's so that when it is set to Normal and I'm plugged into the Gain input, I still get the original "Normal" channel.

As for the old wooden knob, it's a 3-way switch: the 1.5 cath res is always in place, but when switched one way, the 25uF bypass cap is added, and when switched the other way, the cap is taken out and a NFB circuit is connected. I think it's a 56k NFB resistor.

I found the original 5E3 to have much too much break-up than I like, so now I have a great array of options, my favorite simply being the original bright channel with the bypass cap switched out (when the wooden knob is set to 1.5K). There's still plenty of crunch at the right volume :).

In the gut shots, you can see I added a small terminal board next to the tube socket and ran wires across to an ancient 3-way switch I had lying around. Again, I did not notice any great increase in the noise floor. I used some rather ratty old shelled cable for the signal return. The 1.5k cath res and the 56k NFB res are probably hidden under the shrink tube.

Hope that helps.