Screen resistor & grid stoppers - are they worth trying if my amp has none?

[Twosteps]

It's a 5E9A, I just read about it(yes, I'm still learning a few things at a time) and got curious. The amp came after 5E3 which has grid stoppers but no screen resistor, so probably Fender might have had the reason not to have it in this circuit. I don't know. I suppose I could try if it's not gonna hurt the amp. I'm sure it's ok to try the grid stoppers but not so sure about screen resistor with the paraphase PI, actually not even sure where should I put it if I decide to try. Is it safe to try? Thanks in advance for any comments/opinions.

[shooter]

grid stoppers where V1, V 7 
screen R's are used to limit I, fender was having a bad quarter so they left 'em off so the employees could get a bonus check 

[jjasilli]

To make a mod you should gave a goal.  E.g., tone; or safety / fail safe.  Grid stoppers are usually used to kill RF noise, or eliminate blocking distortion.  Not needed if your amp doesn't have issues.


Screen resistors in small values are a safety feature for the screens, limiting current.  In larger values they also shape overdrive tone.

[Twosteps]

Happy New Year!

It's simply because I've read Rob Robinette's suggestion on 5E3 to add 470r resistor on the phase splitter(v2b pin 7) to tame the overdrive slightly. I just want to try & hear it for myself if I like it or not rather than a mod with any specific goal. Kinda like learning - to see it for myself but I'm not sure how & if it safe to do it since it's not the same circuit.

I've also got a little confused trying to read more about it since people seems mix up these terms quite a bit on different forums but it seems like they don't have anything to do with each other right? Adding grid stopper seems straight forward and harmless plus my amp's a bit noisy anyway so I'll pop them in & see.

Thanks!

[Twosteps]

Was reading about it again, I think I get it now. I've got mixed up because of the term "screen grid resistor" made me think the two are the same also some talk about PI tube and the others talk about OP tubes...

[shooter]

"screen grid resistor"

try "re-learning" the names as G1 (control) and G2 (screen)

[Twosteps]

I popped them in, loving the sound. I don't know why or how but it does eliminate some overtone and tighten up the bottom end and the mid, less sizzles on the top end but this circuit still has plenty plus it's a trade off that's worth it for a less farty amp(more definition on the bottom end). I'd say this mod is a must for 5e9a unless all you want to do is to crank the amp and slam the chords.