hmmm. I drew up a vero and built the Orange Citrus without the FAC control (rotary with multi-caps on the input) and I love it, but this one is a bit different since the orange citrus has the eq circuit before the drive/gain stage and this one has it after it. the eq cap values are also different on this 'green' version.
i assume it's supposed to emulate a green amp, which still exist, and was connected to MATAMP and orange when they were connected. I don't know how close it will be to sounding like the real amp though. they are monsterous sounding, just check out the band sleep if you haven't before, and you'll get a taste of how insane they can sound. still would love to see this pedal built.
i'm actually working on building an P2P of a green amp, in the process of buying all the parts, the only parts holding me back is actually how to build P2P, which i know should be easier then i'm making it in my head.
I drew one up but haven't built it yet. i'm 99% sure that it's correct though.
instead of trimmers, I recommend socketing the four resistors for the drains since this type of circuit is a lot quieter (less noise!) with fixed resistors as opposed to trimpots.
one general question about the value of the resistance for setting voltage at Drain: is it circuit dependent? or could i make a small utility with a trimmer to measure the ideal resistance (just a trimmer, transistor socket and 9V/Ground pads) and then put it in the circuit?
So I am pretty new to pedal designs, can you explain what a drain is, how one would measure 4.5v on all drains, and how one would wisely step through resistor values to achieve that? I am really interested in designing this circuit as I am a big Matamp fan. Thanks for the help and I'll be sure to pay it forward!
Jfets have a pinout of Drain Source and Gate. to measure the drain voltage, you just power up the pedal with 9 volts and measure the voltage with a volt meter from the Drain pin to Ground to bias it properly.
if you use sockets for the drain resistors (as specified in the layout) you just keep trying values until the drain measures 4.5V (1/2 of the power supply voltage). all Jfets generally measure differently so all of the resistors may or may not be the same value. I usually start with a 10-12K resistor and go from there.
a higher value will lower the voltage and a lower one will raise it. you're looking to get anywhere from 4.5V- 5V on all of the drains.