Wave Shapers (Serge)

[Tim Cockram]

Sorry about the delay in posting details of the Serge device.

Here goes:-

Take 1/4 of an LM3900
power +12, 0V
connect a 1n4148/914 accross the inputs, cathode to the non inverting input
feedback resistor from the output to the inverting input of say 1.5M 
Voltage control input (Positve only !) to either the inverting or non inverting
 inputs via a scaling resistor Rc.

Audio input to the  inverting input via a blocking capacitor and a scaling 
resistor Ra

You can start with values of 1M5 for Rc and 100-470K for Ra (depending on your 
signal levels).

To get square and pulse waves as well try feeding back some (via a pot till you find your own personal preference)
via a diode (cathode to the inverting input as the output is positive only) in parallel to the 1M5 feedback resistor.

for more info' on the under used 3900 down-load the applications note from National Semicondutors web site.

It is definately worth aquiring a copy of the patent (US 4,306,480)

Tim