Hi Henrik,

I checked the schematics, and it looks like the range of the trigger
voltage cannot be extended on the A-155, because there a CD4053 is used
as switch, which can switch only 8 V as far as I know. But you might add
a simple "pushup"-addon pcb. It requires one opamp (or two transistors)
and three resistors per channel. Not too difficult of you are able to
solder.
Similar for the Voltage: also here a CD4053 is used in the S&H stage. So
the output voltage is limited. And again, a simple DC amplifier could do
the jobe here (does not need to be precise, because you trim the real
voltage with the pots anyway).

Florian