Adding GR meter to Craig Anderton compressor using second vactrol?

[Blue Jinn]

Hello,

Assumption: I can borrow the meter circuit from Johan Blomdahl's "LA-Light" (top schematic) and wire a second (NSL-32) Vactrol with the LED in opposite direction. The "LA-Light" uses VTL5C2's that are on: 200Ω/40mA,  dark 1M/24mA. The NSL-32 is 500 and 500k respectively, but I don't see the values for the meter circuit requiring any adjustment. (The component numbers are my own notes.)

The question: I'm assuming I'm doubling the current draw by adding the second LED, so I'd need to halve the 1k5 resistor (R1) driving the vactrol LEDs. I can't seem to get the math to work out from the datasheet for the CLM6000/NSL-32, but it seems logical. Anyone see any problems?

 

[abbey road d enfer]

Hello,

Assumption: I can borrow the meter circuit from Johan Blomdahl's "LA-Light" (top schematic) and wire a second (NSL-32) Vactrol with the LED in opposite direction. The "LA-Light" uses VTL5C2's that are on: 200Ω/40mA,  dark 1M/24mA. The NSL-32 is 500 and 500k respectively, but I don't see the values for the meter circuit requiring any adjustment. (The component numbers are my own notes.)

You'll probably need to adjust the 68k and 47k resistors (R6 & R14) in order to get a usable reading.

The question: I'm assuming I'm doubling the current draw by adding the second LED, so I'd need to halve the 1k5 resistor (R1) driving the vactrol LEDs.

No. That would be true if the LED's were in parallels, but they are in anti-parallels, so when the voltage is positive there is no change, though it's different when the voltage is negative.

 

[Blue Jinn]

Thanks! I do have some notes from another try at this adjusting the meter resistors for a different vactrol.