Posted on Feb 5, 2014

The MFOS NOISE TOASTER circuit consists of seven main components: a voltage controlled oscillator, a white noise generator, a voltage controlled low pass filter, a low frequency oscillator, a simple AR envelope generator, a simple VCA, and a one watt amplifier that drives a small speaker. The unit is powered by one nine volt battery and due to the

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low current drain of the LM324 (Lo-Power Quad Op Amp) it gets a lot of miles out of a nine volt battery. The circuit draws about 15mA to 25mA dependent on volume level when using the internal amp. When using line out the unit draws slightly under 15mA. The voltage controlled oscillator (VCO) in the NOISE TOASTER provides a nice wide range of frequency and two waveforms (ramp and square). It is known as a ramp core design since the main waveform results in a ramp wave. In a modular synthesizer this wave would be converted into several other waveforms through various electronic techniques. In the NOISE TOASTER this wave is also converted to a square wave. IC U1-C (1/4 LM324 Low Power Quad Op Amp) is used to sum the control voltages that modulate the frequency of the VCO. Three sources of frequency modulation are applied to this op amp which is used as an inverting summer. Potentiometer R1 (100K linear pot) is used to control the frequency of the VCO. It`s ends connect to BN and BP (Battery Negative and Battery Positive) thus the wiper sees from 0V (min setting) to 9V (max setting) which is applied via R2 (75K 1/4W resistor) to the inverting input of U1-C. Potentiometer R13 (100K linear pot) is used to control the amount of LFO modulation applied to the summing inverter via R14 (100K 1/4W resistor) to the inverting input of U1-C. At minimum setting it applies BN to the summer and at maximum setting it applies the LFO output...

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