The original TB-303 had a kill switch hooked up to the LA 4140 (Headphone Amplifier), which makes sense, because the LA44140 is the only draw of the +6Volt power.
This is entirely theoretical, but you might be able to change the circuit so that the LA 4140 can be used as a Distortion, and/or EQ circuit.
You'll need the Datasheet If you are going to get far with it.
|Schematic||Power Supply||Voltage Controlled Oscillator||Voltage Controlled Filter||Envelope Generator||Voltage Controlled Amplifier||Headphone And Mixer||Digital Sequencer||Midi, USB and Sync|
|Fabrication||Building the Ps||Building the Vco||Building the Vcf||Building the Envelope||Building the Vca||Building the Headphone And Mixer||Building the Sequencer||Building the Midi and Sync||Finishing It Off|
|Testing||Testing the Ps||Testing the Vco||Testing the Vcf||Testing the Envelope||Testing the Vca||Testing the Headphone And Mixer||Testing the Sequencer||Testing the Midi and Sync|
|Mods||Ps Mods||Vco Mods||Vcf Mods||Envelope Mods||Vca Mods||Headphone And Mixer Mods||Sequencer Mods||Midi And Sync Mods||Finishing Mods|