Mellotronists

[thanks in advance folks]

i have recently picked up a couple lexicon effects units on ebay
for some decent prices. a reflex and an mpx-100. i've had an lxp-1
for years and have been very pleased with it, particularly as a
reverb unit - amazing for the price.

i have had the lxp-1 on my main console effects bus for years,
with no level problems at all. i have also used it as an insert
effect, again with no level problems.

but... both the reflex and mpx-100 are giving me fits when used
as insert effects from a mackie i use as a sub-mixer. they seem
to be expecting a guitar level signal, and i can barely use the
input knob at all to control the input level. turning it just a
tiny tiny bit causes the input level to overload. the input i also
too hot when used on the effects bus - again, it seems like it's
looking for a guitar level signal :(

so i have a really stupid question:
what can i use to "pad" the input signal so it doesn't overload
the inputs? [keep in mind that i use these 'stero-in/stero-out'
so i would probably need 4 of whatever i'll need]

is there some simple way to match these levels?

would i have to change the values of the input level pots?

my old delay units have level pad switches to fix this problem.
the lexicons have no pads - just the input level knobs.

thanks again in advance.
jeff