Paranormal Compressor Schematic - Guitar Magazine

[Rob Strand]

Thanks Rob, you're great as always! Will try those models in the morning, now time to sleep

I wasn't clear about something:
MZVN4106_ZTX    this one is good for higher bias currents
M2N7000_ROB     this one is good for low bias currents like you get in effects.

If you build an amplifier with a low valued (or cap-bypassed) source resistor you will find the M2N7000_ROB model gives closer results.  The MZVN4106_ZTX model will produce much higher predicted gains.

[rankot]

OK, I've tried it this morning and with Rob's 2N7000 model it works like with almost any other MOSFET I have in library - signal is actually very weak, some ±60uV at output, with ±100mV input:


With CD4007 based transistors, I get much better results ±20mV at output, with ±100mV input:


Output is slightly bigger if I connect Compress pot CW to output, instead of the point marked with COMP_FEED.

So maybe I'm just missing something here?

[Rob Strand]

So maybe I'm just missing something here?

Your Drain resistor R3 is 100k it should be 10k.

I did simulate this and I got it to work before I sent the files to you.
It has some quirks but it more or less works.

If you can show the DC voltages on your schematic you should see the drain voltage of Q1 stuck at the same voltage as the source because R3 is too large.  (And yes you will see that problem will all MOSFET models.  The CMOS gate is closer to working because it is the weakest.)

[rankot]

Your Drain resistor R3 is 100k it should be 10k.

You're right, I've misread the value from photo 

It works now.

[Rob Strand]

It works now.

Cool!