orange squeezer / cupcake biasing guide - super useful!

[the3secondrule]

Found this amongst some notes - i think it was cut n pasted from DIYSB - can't remember the source, but I just used it to get my cupcake sounding great!

"I was perusing through a pile of old Japanese schematics instead of working like I should be, and noticed something called an "Orange Clash".  On closer inspection it was very clearly a note-for-note/part-for-part clone of an Orange Squeezer.  Although the accompanying text is in Japanese (which is Greek to me!), the schematic shows an arrow pointing to the place where the trimpot, 24k resistor, 4u7 cap and gate of the secondary FET are tied to the source of the principle FET.  The schematic indicates that, with a 9v supply, this trimpot should be adjusted to read between +1.5 and +1.7vdc.  Obviously you can take that reading at any of the aforementioned components where your probe conveniently fits.

It also indicates a DC reading of +4.9V on the output pin of the op-amp, just before the 4u7 output cap, and a probable peak envelope amplitude of around 1.7V where the diode meets the 470k and 100k resistors."

hope this is useful to someone else!

J

[toneboner]

possible typo or part substitution, but the 24k mentioned looks like a 2k4 (R5) in the cupcake build...
i'm not super keen with how all these thingees work but seems like that will have a big influence on what that 2nd fet is doing and perhaps on the range of the trimpot as well. could be why the trim has such a small effective range?

way out of my element here. suppose i'll have to grab my iron and meter and do some tinkering

[Jazzman]

Hey, this really helps... thanks 3secondrule! 

[jtn191]

reviving this thread just to say thanks and:
For Tayda FETs, I found ~2.6v to be the lowest distortion free voltage. Anything above that is less compression.
"where the trimpot, 24k resistor, 4u7 cap and gate of the secondary FET are tied to the source of the principle FET"