Table of Contents

Testing and Calibrating the VCF

Testing

  1. Re-attach the power supply (with J4)
  2. Apply 3volts to R90 (either with 2 AA batteries or a benchtop supply)
  3. Probe the resonance pot with either a cheap pair of headphones or your oscilloscope. With the cutoff all the way anti-clockwise, you should see mostly a sinewave. If you're probing with headphones, you should hear a low, soft tone. When you turn the cutoff up, you should see a waveform similar to the one you have selected on the VCO. Using headphones you should hear a lot of higher overtones to the sound, and it might be buzzier and more 'acidic'.

Calibrating

According to the TB-303 service manual, the resonance frequency should be at 500Hz.

  1. Set the waveform to saw
  2. Set Cutoff to 50%
  3. Set Resonance to 100%
  4. Apply 3V DC to the VCO (or press the lower C key if your sequencer is done)
  5. Ajust TM3 so that the resonance frequency is 500Hz
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