Moving the 68k's to the sockets

[angelodp]

Marshall Super Lead builders, do you move the 68k's to the tube sockets? Best practice would be to have those grid resistors right at the socket eyelet.

[Colossal]

Yes

[angelodp]

Ok so with those 4 - 68k's - 2 per each pair of inputs, what does that look like. Two shielded runs with 68k at the eyelet to the V1 grids combining the input leads. Any layouts you can point to, I am keeping the 4 input jacks.

[Colossal]

Ok so with those 4 - 68k's - 2 per each pair of inputs, what does that look like. Two shielded runs with 68k at the eyelet to the V1 grids combining the input leads. Any layouts you can point to, I am keeping the 4 input jacks.

I run four shielded leads, one from each of the four inputs. Each lead gets a 68k resistor, with two soldered directly to pin 2 and two to pin 7 on V1. Ground each shield at the input jack the lead is serving. Bundle four shielded leads neatly and ziptie in two or three places.

[angelodp]

Perfect thanks Dave

[Leo_Gnardo]

FWIW I've also done this, also on Fenders and other amps as well. Good build practice has it that "stopper" resistor(s) should be as close to the tube grid as possible, in spite of the way major manufacturers have been doing it for decades. In lower gain amps, generally not necessary to use shielded wire. But those who want to, can use shielded. Can't hurt.

[pdf64]

Yes, generally, with regular 4 hole type amps, screened cable from jack to grid stopper at valve socket' is some way off being necessary, plenty of margin of stability available just with good lead dress.
But as a belt and braces, it won't hurt.
If doing so, maybe use mini mic cable with 2 cores, to keep things tidier than it might be with 4 individual single core cables

[Colossal]

If doing so, maybe use mini mic cable with 2 cores, to keep things tidier than it might be with 4 individual single core cables

I've done this with Belden 2-conductor shielded too and it keeps things neat.

[thetragichero]

any potential for crosstalk between the two conductors that way? I've got a ton of small organ-salvage shielded wires so i do em individually, but I'm curious regardless

[Leo_Gnardo]

any potential for crosstalk between the two conductors that way? I've got a ton of small organ-salvage shielded wires so i do em individually, but I'm curious regardless

Ha, I was gonna say "oh, the crosstalk!" whilst clutching my pearls... but no, not really. As long as you wire the dual core shielded from a hi/lo input pair with both conductors headed for the same triode, then what's to worry about? Typically one plugs into either the full strength input, or occasionally the padded input. Rarely does anyone plug into both, unless you're on a super tight budget for stage gear. Paul and John into Chan 1 high & low, George and Ringo into Chan 2 high and low. Mighty rare to use an amp that way, though my low budget college band did in 1971. Ah, the bad old days. Rehearsals sounded like dog meat, phooey. Bass notes & vocals didn't get along, poor girl singer sounded like she was gargling. I reckon the unfriendly modulation was further down the chain of amplification. Lucky we did have separate amps for actual performances.

[thetragichero]

my thoughts were more in line with jumping the channels like one would with a 4-hole Marshall. maybe this is where visualizing current flow as water breaks down

[pdf64]

my thoughts were more in line with jumping the channels like one would with a 4-hole Marshall. maybe this is where visualizing current flow as water breaks down

Surely jumping the inputs ensures 100% ‘crosstalk’? ie the input stages of both channels will be, to all intents and purposes, linked, and so they process the same signal.
What gets to the second stage is set by the vol controls. The particulars of the cabling from jacks to valve socket doesn’t appear to be relevant to this scenario.

[angelodp]

Something like this