#1
I just bought a Marshall JVM 205C combo. My old amp was a piece of crap and only had treble, mid, and bass knobs. I've been working on my tone and have no idea what the presence and resonance knobs do.

Help would be greatly appreciated
#3
Actually, I thought the Marshall user manual did a good job of explaining it

http://www.marshallamps.com/downloads/files/JVM2%20hbk%20Eng.pdf

PRESENCE, RESONANCE (6)
These controls are power amplifier controls and
only have effect when playing through a speaker
(not in silent recording). They affect how the
power amplifier reacts to the connected
speakers and how much control the amplifier
has over them.
Increasing the RESONANCE control
emphasises the natural speaker’s resonance for
an improved bass response. In the same way,
increasing the PRESENCE control emphasises
the speaker’s high frequencies which will be
heard as an improved high frequency response
which adds presence to the sound.

Presence and Resonance constitute a powerful
power amplifier equaliser, allowing responses
from a ‘^’ shape when they are fully
counterclockwise, which is felt as a mid boost,
to a ‘v’ shape when they are turned clockwise,
which is felt as a scooped sound. Again, the
effectiveness of these controls is highly
dependant on the kind of connected speakers.
Care has to be taken to avoid over excursion of
the speaker cones in high resonance settings.