[sdiy] SSM2164 last time buys

[Colin f]

> The problem I'm trying to solve is the lack of a negative 
> supply when ground and positive supply are present. I'd like 
> to have the positive supply be disconnected if the negative 
> supply becomes disconnected. And, I suppose, the solution 
> should also disconnect the negative supply if the positive 
> supply is not present.

Why not derive the ground reference from the positive and negative supplies
?
Two resistors and an op-amp.

Cheers,
Colin f