◊ PCB Documentation


Basic LFO

Bog-standard LFO oscillator.

  • 4 outputs:
    • Square (50% duty cycle)
    • Pulse (varible ducy cycle
    • Variable shape (from ramp to try to saw)
    • Inverse of variable (saw to tri to ramp)
  • 2 (or 3) controls:
    • Duty cycle varies percentage of "on" time of pulse, and the shape of the variable outputs
    • Speed control, in combination with the timing caps, controls the rate.
    • Rate switch adds a second timing capacitor in parallel with the first; cap values can be adjusted to taste

Useful for general purpose LFO sweeps (filters), tremelo (when applied to an VCA) or vibrato (applied to a VCO) effects, or as a clock source. Mirrored versions of the Variable waveform can be used for complementary filter voices or panning. Modify or omit features as needed — for instance, use a single small timing cap, disable the shape control, and combine it with the 208 Random module for a dedicated free-running random generator.

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Bill of Materials (value/qty)

  • Resistors
    • 1k x 4
    • 2k2 x 1
    • 4k7 x 1
    • 47k x 1
    • 100k x 3
    • 100k linear pot x 1
    • 500k linear pot x 1
  • Capacitors
    • 100 nf x 2
    • 220 nf* x 1
    • 2.2uf* x 1
    • 10uf x 2
  • Semiconductors
    • 1n4148 diode x 2
    • 2n3904 transistor x 1
    • TL072 quad opamp x 1
    • TL074 dual opamp x 1
    • LED x 1
  • Misc
    • ferrite beads x 2
    • SPST switch x 1
    • .156" pitch/4 position power header x 1
    • .100" pitch/2 postion header (for range switch) x 1

*Slow (2.2 uf) and fast (220nf) timing caps, adjust to taste