[sdiy] Overdriving 4069UB - Final Circuit

[Seb Francis]

Well, after much agonising over how to protect the 4069 input I've 
decided to up the input resistor to 100K (and increase the feedback 
resistor proportionally).  This has made absolutely no difference to the 
sound and the current through the 4069 internal protection diodes 
shouldn't now exceed ~0.05 mA.

Also, there was a mistake in the input pot & opamp configuration before 
- now there should be an almost perfect log response from the 100K 
linear pot (by having the 12K resistor to virtual ground at the opamp 
input).  The linear pot output volume control should also have a good 
log response providing it's driving something with a fairly high impedance.

http://burnit.co.uk/sdiy/stuff/mosfet_distortion.gif

Thanks to those who gave help and advice :)

Seb