Marshall "Hot Shield" on input...yank it or crank it?

[SpiderWars]

That '80 JMP MV I just bought has the input jack going to the board where the 68k series resistor is, then at the other end of the 68k there is a shielded cable going from the board to the B section of V1 with signal to pin 7 and shield to pin 6. The "hot shield". Do you guys feel this affects tone? Those 2 signals are out of phase with each other right?

Since the input jacks on this amp feel shitty I was thinking of just replacing them and then a shielded cable straight from jack to a grid stopper mounted right on the socket. But what type of snubber on V1 now? 100pF from plate to cathode? I think the hot shield acts as a snubber of sorts.

 

[Chubbs]

Kinda hard to tell without pics. Mine has stock sheilded cable from V1 to the 68k, then standard hookup wire to the input if that helps. I like a 470pf snubber but that's just me.

When I experimented with different types of wire I found hookup wire would squeal, and coax cable depending upon type would darken the tone a bit.

 

[RedPlated]

I made a tutorial on this a couple years ago. I do it a little different now and mount the resistor standing straight up off the tube socket. But you get the idea. Info is about 1/4 way down the page...

https://www.rig-talk.com/forum/thre...k-1982-jcm-800-2204-today-clip-inside.213840/

 

[SpiderWars]

I made a tutorial on this a couple years ago. I do it a little different now and mount the resistor standing straight up off the tube socket. But you get the idea. Info is about 1/4 way down the page...

https://www.rig-talk.com/forum/thre...k-1982-jcm-800-2204-today-clip-inside.213840/

Cool, thanks. I was going to just try to ground each end the old wires so it's more easily reversible. So you didn't use any snubbers at all and didn't have any stability issues? Shielded cable and a socket-mounted grid stopper is enough?

 

[RedPlated]

No snubbers needed. Just shielded coax from input to 33k grid stopper to tube. Zero stability issues.

The stock shielded input is only shielded from the board to the tube, a very short distance. Replacing the cable with coax makes the entire run shielded.

 

[SpiderWars]

OK done. Not a ton of difference but it does seem to break into harmonic feedback easier and it seems a tiny bit less honky in the mids. But it took a while so my ears were different. Now that I've addressed the low hanging fruit like bias, a new Power Switch that actually lights up, sketchy fuse holder, fubar mounting nuts, and the whole input jack/hot shield...I can play it for a bit before go in and replace the bias filter caps.

I found my old SD1 that I thought was dead but nah, still works. It's like they were made for each other. My old Marshall Drivemaster works pretty good too.

 

[RedPlated]

Some 2203/2204’s are more muddy than others stock. The 2204 in the post I referenced was significantly better with the hot shield removed. Very noticeable difference. Some of us hear things different though.