A better switching vactrol?

[NorCalTuna]

I use lots of vactrols, the typical 1 and 4 types used in boogies. I'm setting up a switching system kind of like a mk3 lead channel and have been poking at the datasheets. It seems like, at times, the 5c1 may be being operating outside of it's spec'd cell voltage, 100v. There are 200 and 250v cells but they're not suitable for other reasons. Now, I find the VTL5c8, it's got 500v cell voltage, and an even faster slope than the 1 part. It doesn't have the 100db dynamic range- 80db or the dark resistance of the 1, but seems like it's more appropriate spec wise, as the swing of an overdriven preamp tube can be pretty wide. Isn't 80db enough?

I guess I'm asking if I'm being paranoid over specs or if the 8 wasn't available when these applications were being designed?

Thanks!

[imaradiostar]

I think it depends how the part is implemented. Most Mesa amps use the vactrol with a coupling cap/resistor ahead of it so the vactrol only ever sees the AC voltage, not the plate voltage of a given stage. There are probably exceptions but I recall that most vactrols are placed so they never see the huge swings.

If you place them at appropriate places in the circuit the dynamic range should be less of an issue. If you were using them for automatic gain control or a compressor it could be a problem but I assume you're using them as a switch.

What is the difference between the on and off resistances? I'd be more worried about them turning off well (have lowest possible on resistance) than about a particular dynamic range. This is where relays excel, of course!

jamie