Never heard of a vactrol so just looked it up. It appearers to be a simple opto isolator using just an LDR and a diode. Is that what you mean? If so it's not doing much for you.
Indecently back in 1967 I "invented" the opto isolator (it was my idea and no one had done it at the time) only LEDs hadn't been invented as a commercial product and I used a cadmium sulphide LDR and a flash light bulb in a cardboard tube. It worked as well although it was very none liner.