Hi Michael, from Japan.
I started my career of Alembic with Distillate Bass at 1981.
When I got Series Instruments, I was worried "Powered or not".
If you have the same idea, I have some ideas.
1: Do you use only 5 pin cable ?
I always use 5 pin cable. Older DS-5 has no power indicator, so I made LED cable.
The LED lighted when plugged it & works as cable checker for both circuits (plus & minus 18V).
2: Do you want LED when the 1/4 phone plugged in ?
The series instrument runs 2 batteries for ± 9V. But Series circuit is battery eater.
So I don't recommend additional LED load.
I think the LED works simply powered from 1/4 jack, but routing is difficult and irreversible.
3: Do you want Wireless environment ?
I recommended external battery box (4 batteries included) as Mark King used it.
Additional LED on 5 pin is fine.
I made LED cable and Ex.battery box at 2004. Both works fine !
https://club.alembic.com/index.php?topic=2820.msg31616#msg31616Eiji from Japan