Grid stopper value?

[daz]

In my quest to try and make my classic 30's power section more articulate and agressive, i've been trying to get answers on an OT swap. But someone who looked at the schematic mentioned that the grid stoppers are very high and suggested that changing those might help. They are 47k, and sure enough looking at other amp schematics thay are all far lower in the 1.5 k area. Any thoughts on this and why peavery uses such high values and whether it's necassary in that amp for some other reason in the design? heres the schematic...

http://www.blueguitar.org/new/schem/peavey/c30schem.gif

[HTH]

47k does seem on the high side compared to other amps. 1k5 or 2k2 seems a typical Fender value and 5k6 is typical for Marhsall.

The only other amp where I've seen grid stoppers that high is Marshall's Studio 15 amp where they use 100k.

I'm sure one of the more 'techie' types will wade in and give a proper explanation of whats going on.

[Ray Ivers]

daz,

Any thoughts on this and why peavery uses such high values and whether it's necassary in that amp for some other reason in the design?

It could be that they wanted to isolate the PI from the power tubes to improve PA balance during dimed operation, increase stability, etc.

FWIW, optimizing the V3 circuit for a 12AT7 sub might help your PA operation at higher power levels - if this is something you might want to try, let me know and I'll work up some component values for ya.

Ray

[daz]

daz,



It could be that they wanted to isolate the PI from the power tubes to improve PA balance during dimed operation, increase stability, etc.

FWIW, optimizing the V3 circuit for a 12AT7 sub might help your PA operation at higher power levels - if this is something you might want to try, let me know and I'll work up some component values for ya.

Ray

Thanks Ray. But i think i'll leave that. I'm really more interested it what will make the amp more organic at low levels as much as stage volumes. In fact, even MORE so because i rarely play out anymore so bedroom levels are important. I just took the NFB out of circuit and that made a nice difference right there.