Grid stopper question

Impetus

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Hi, just to preface I'm not talking about on pin5 on power tubes. I attached a picture below and i'm wondering if this in theory should be identical to having the regular 68k input mix resistors? This amp use to squeal quite a bit turned up. so the 68k input mixers are disconnected on the board and are instead two 33k instead of two 68k resistors on each channel connected at the input jacks then leading to their own 10k grid stopper on v1 preamp tube as well as another 10k grid stopper connected to v2 preamp tube (three 10k grid stoppers all together) The 33k compensates for the difference with having the extra 10k grid stoppers? How accurately would this reproduce the stock sound of 68k input resistors without grid stoppers?
 

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neikeel

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Remember 68k + 68k in parallel = 34k (ie same). You would be better off removing the grid resistors off the inputs, removing the 10k and simply using 33k on each socket, keeping your leads short as possible. BTW by floating all your wires from the board in the air you are creating antennas, but particularly the brown grid wire to V2 that is cozying up to the plate wires.
Too many grid stoppers attenuate your signal and are essentially elastoplast stuck on to compensate for other issues.
 

Impetus

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Remember 68k + 68k in parallel = 34k (ie same). You would be better off removing the grid resistors off the inputs, removing the 10k and simply using 33k on each socket, keeping your leads short as possible. BTW by floating all your wires from the board in the air you are creating antennas, but particularly the brown grid wire to V2 that is cozying up to the plate wires.
Too many grid stoppers attenuate your signal and are essentially elastoplast stuck on to compensate for other issues.
So right now I've got more like 16k then since I'm using two 33k in parallel? So you're suggesting either use a single 33k or the standard two 68k in parallel which is basically 33k anyway? As well as remove the three 10k grid stoppers...will do! Also I will take care of that brown wire. Honestly, if I like it better after removing the grid stoppers and all that then I should probably just wire back up to stock using the 68ks on board, right? That way I wouldnt be using those long wires all the way from the input jack to the tube.. Would you leave the 5.6k grid stopper on pin 5 for the el34's on a jtm50? I've thought about trying 1.5k there but havent really had a reason to I suppose, just curiosity but I've never seen an older marshall with those grid stoppers on the power tubes besides jtm100's and havent seen a single jtm50 with any value there

Btw I read up on some books i bought at the recommendation of you folks! Been quite the learning process
 

South Park

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It looks like those resisters are hooked to the shield to ground on the input . You might have a ground loop thar . Restore to stock specs put the 68k grid stopper on the tube socket with shirk wrap ground the shield to ground on the jacks . You can put the grid stopper on the board or tube socket
 

Impetus

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It looks like those resisters are hooked to the shield to ground on the input . You might have a ground loop thar . Restore to stock specs put the 68k grid stopper on the tube socket with shirk wrap ground the shield to ground on the jacks . You can put the grid stopper on the board or tube socket

I know the grounding on this particular amp isnt stock. The pots arent bussed together etc..but this would cause a ground loop with the way those input resistors are connected to the jack? I'm a little confused, I should put the 68k resistor on the tube socket? Or do you mean 10k resistor? I would like to maybe completely remove the 10k resistors since they arent stock marshall anyways
 

South Park

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Get the wire layout of that amp and follow it to the letter . Ground loops can be on any ground connection it is what is connected to what that makes a ground loop . Some amps have grid stopper on the board . If no room on the board you put them on the socket . The buss wire on the pots is not needed the grounds are linked together you can do them ether way .remove the 10k resisters
 

Impetus

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Get the wire layout of that amp and follow it to the letter . Ground loops can be on any ground connection it is what is connected to what that makes a ground loop . Some amps have grid stopper on the board . If no room on the board you put them on the socket . The buss wire on the pots is not needed the grounds are linked together you can do them ether way .remove the 10k resisters
I just saw what you mean by the resistors looking like the were connected to ground. It does look like that. The bare wire you see is actually just holding those other wires in place a little better. It definitely looks like theres another connection from it though if the bare wire is what you are referring to?
 

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