looking at the Cub II & viewing the manual, i found the input
gain switch description/usage to be a little 'cryptic' (to me)
high (sensitivity/impedence) - passive or magnetic pickups
high impedence is a hi-Z, unbalanced signal, which can come from a 1/4" tip/sleeve output
not all magnetic pickups are passive, as LR Baggs & Fishman, to name 2,
make low-impedence magnetic pickups (M1 active & rare earth humbucking)
with balanced 1/4" TRS out, which allows a second source to be added
low (sensitivity/impedence) -
onboard electronics (active, balanced out 1/4" TRS or XLR) &
a quality 1/4" TRS to 1/4" TRS instrument cable will usually
have the same effect as a 1/4" TRS to XLR cable with the ES
XLR inputs are usually designed for line-level devices (mics)
which mean the amp would 'boost' the input signal, assuming it
does not have phantom power, which may be problematic when
using a instrument with an active pick up (a 'hot' input signal)
many dual source pick ups have a balanced output, such as the LR Baggs Anthem &
Fishman stereo blender, but not all guitars with onboard electronics (EQ) are
active & if the guitar has an unbalanced out (1/4" tip sleeve), using a
1/4" TRS to 1/4" TRS cable may result in no signal going to the amplifier
the Shadow P7 is an active (9V) single source UST
with onboard pre-amp & a hi-z (unbalanced) 1/4" out
if the signal from the ES is too 'hot' using the balanced cable &
lo-Z input (if it requires too much 'pad' or gain cut at the guitar &
or the amp), i would use the hi-Z unbalanced input or flip the switch
ymmv
