HelpingFriendly said:
Does anyone know which cap is the one that is used for the "bright switch" on R1? (pull volume)
I am interested in altering it to be a smidge less bright
Yeah, it is the 100-180pF cap that is on the switch on the back of the first volume pot if that's the one your talking about. Technically this value of cap isn't very big in comparison to many other designs (Old Marshalls have a 5000pF cap here), so increasing it or lowering it's value won't actually reduce the perception of brightness. What you would need to do is add a series resistor to the cap; this effect is similar to how a tone pot on a guitar works. In fact the mod I'm describing is a popular guitar mod, in one variation it is called the 'Hendrix mod'. What you would need to do is snip off one end of the long lead that goes from the switch to the center lug of the gain pot, then replace that snipped off section with a resistor. The value of the resistor is completely dependent on taste and how much bright you want to cut; for a very subtle cut I would start with a 10k resistor and for more cut anything up to 100k. One variation you might like is what the Lonestar does, it uses a 120pF cap in series with an 82k resistor; since the LS doesn't have a dedicated bright switch like the MarkIII has, this is a really clever compromise to allow some added sparkle as the gain pot goes down without it getting peaky and piercing.
