Hi T: thanks, looking forward to it. I'm going to use it to re-wire the inputs on one or maybe both of the GA20Ts linked in my siggie. Channel one in these amps has two input jacks that, oddly, each lead to one 1/2 of the first gain stage; the stages are not in series or daisy-chained; when plugged into one jack, the other 1/2 of the tube sits idle doing nothing.
At one point, I thought about bringing the input from one of the input jacks into a DPDT switch sitting in the other input jack's hole. With that switch, I could switch the input from one side of the tube to the other and switch cathode resistors and bypass caps with the other switch leg. I shared this with the Chairman of New Zealand's South Island LTG chapter and Class A certified electro-noodler. When he chooses, he can be a very polite guy and said; "Cheese Juan, are ya nuts or what? Why don't you just re-do the cathodes the way you want, leave them alone, and switch the input only between the two tube halves?"
Well, I says (to meself): "Thank God for kiwi fruit!"; he's right, I don't need to switch both inputs and cathodes, the inputs will do just fine ... so ... I need the shielded cable to jump from the remaining channel 1 input jack to the switch and then two shielded legs; one from each switch lug to each tube half input grid. At the end of my GA20T thread, there's a sketch showing the planned new cathode resistor and bypass cap values; what I want is two distinct amp voices from the same input jack available by a switch; lighter/brighter vaguely Marshall-esque in one switch position and meaty, chimey, smokey 'tweed' tone from the other.
If you didn't know, nearly every wire in an amp is susceptible to picking up electromotive force (EMF), stray eddy currents, radio frequencies, Swine Flu, and Sexually Transmitted Diseases. Shielding the input wiring keeps it from acting like an antennae; one end of the shield wire is grounded .. typically at the jack end to the chassis. The only issue that presents is that this shielded wire is #16; a size challenge to the grid pins that are small, punched tabs that usually host #18 and #20 wire. I don't think it will be a problem but, as a talented ampista on another BB says: "Plan on having something go wrong". Thanks again, John