Basic LFO
Bog-standard LFO oscillator for general-purpose use. Low parts count, runs on +/-12 or 15VDC. Can be panel-mounted via two pots on .75" centers. PCB size: 2.75" x 1.75".
- 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)
- 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.
Bill of Materials (value/qty)
- Resistors
- 1k x 4
- 2k2 x 1
- 4k7 x 1
- 10k x 7
- 47k x 1
- 100k x 3
- 150k x 1
- 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
