"Dull Cap" Location Relevance

[thisismyname]

Is there any difference between placing a single 47pF< cap across a plate load resistor, in the NFB, or across the PI plates?

Is there any use in putting a 10pF-47pF dull cap in multiple stages to control the super high frequencies that cause oscillation or would a single location (like the PI plates) be good enough?

[10thTx]

Difference in what regard? You have not even mentioned what kind of amp it is? Is there a problem with oscillation? Do you know what's causing the problem if there is? Or is this an aim for some added smoothness to the tone? You haven't posted a schematic?

Yes, there can be a difference in how it affects the tone.

Yes, sometimes it can be useful.

It might or might not be sufficient in one place.

Honestly, IF you know how to work on amps safely ………………… get some insulated alligator clipped wires and hear it for yourself.

There are so many factors that would come in to play to give a definitive answer, that it would likely be more useful in trying this and see what sounds best to you.

With respect, 10thtx

[Stevem]

There are two types of needs for caps used in this regard, and to me that can really dictate where they need to be added to the circuit at times!

If you just want to roll off some harsh high end in terms of clean sounds then a cap can perform that function in a number of places!

On the other hand if your taking about harshness and or oscillation problems when clipping is taking place then I have found it best to first implement a cap on the plate of the gain stage that is clipping the hardest.
A lot of hard early clipping make for a whole bunch of harmonics to be produced above the root note(s) being played.
These combinations of 3rds , 4ths, 5ths and 7ths and such can sound very brash, spiky and even make root notes and fifths being played at the same time with each other sound out of tune, no less send a amp off into oscillation maybe!