VCO with LFO
At the right-hand end of the breadboard is a voltage-controlled multivibrator based on a circuit from 4QD-tec: www.4qdtec.com/mvibs.html
The frequency is variable over a 100-900Hz range by the control voltage. The transistors are PNP 2N3703s and NPN 2N3704s. The timing capacitors are 0.1μF. The silver knob alters the control voltage, which linearly controls frequency.
The control voltage of the VCO is modulated by a sine-wave generated by a phase-shift oscillator on the left-hand end of the breadboard. This part of the circuit is based on one in R.M. Marston's "Diode, Transistor and FET Circuits Manual", p97. The original runs at 800Hz, but I've increased the capacitors to 1.0μF (the big blue Philips ones) to get the frequency down to 8.2Hz The transistor is a 2N3904.
VCO with LFO
At the right-hand end of the breadboard is a voltage-controlled multivibrator based on a circuit from 4QD-tec: www.4qdtec.com/mvibs.html
The frequency is variable over a 100-900Hz range by the control voltage. The transistors are PNP 2N3703s and NPN 2N3704s. The timing capacitors are 0.1μF. The silver knob alters the control voltage, which linearly controls frequency.
The control voltage of the VCO is modulated by a sine-wave generated by a phase-shift oscillator on the left-hand end of the breadboard. This part of the circuit is based on one in R.M. Marston's "Diode, Transistor and FET Circuits Manual", p97. The original runs at 800Hz, but I've increased the capacitors to 1.0μF (the big blue Philips ones) to get the frequency down to 8.2Hz The transistor is a 2N3904.