Tremolo Effect Circuit for Electric Guitar

 

Tremolo circuit is a kind of sound effect. We can see this type of effect is applied  in guitar effect pedals.  Tremolo effect is produced if we modulate the amplitude of an audio signal. The shape of modulating signal can vary from square wave, sawtooth wave, or sine wave. When we use a square wave, then the effect produce a knocking-like sound which might be perceived like a percussive instrument.

Time Manipulator Circuit

This is a design circuit for a type guitar effect. This circuit can be used as delay, reverb or echo because this circuit is use time manipulator. It uses two PT2399 delay integrated circuits to archive up to 600ms delay. Also, with the help of 4 analog switches, the internal configuration of the pedal can change: placing the PT2399 delay chips in series or parallel and adding extra features. This is the figure of the circuit;

Frequency Modulator and Tuning Circuit

Here’s a design circuit for frequency modulator that is completed with tuning circuit. In this circuit is using pair of 1N4007s are used as varactor diodes. I picked 1N4007s not because they are particularly well suited, but simply that I had some on the bench. One of the varactors is directly coupled to the xtal circuit through 1 nF so most of its capacitance change is seen, the other is coupled through a small trimmer to adjust its maximum effect. This gives two independent channels, one for relatively coarse frequency tuning, the other for FSK modulation. Here’s the figure of the circuit;

The data looks characteristically parabolic as expected. I suspect the oddness of the fine is measurement error. The y coordinates are in Hz relative to 10.138000 MHz (x is reverse voltage) so it doesn't take much error in measurement to make the fine trace look lumpy.

TC9400 VFC for PLL FM Demodulation

FM demodulation can be done with phase locked loop (PLL), and this method is  common in high-end communication system. This system uses TC9400 that has high linearity. Using TC9400, the performance of phase-locked loop will increases greatly. That will give very precise tracking of Vout with respect to Fin. This is the figure of the block diagram;

The operation principle is very simple, since the feedback system force the V/F converter (VFC) to follow the FIN by manipulating the control input of VFC,  as the result, the control input of VFC will follow the variation  of  FIN. This control signal is then tapped for the output of this circuit. [Block diagram source: Microchip Application note]

PLL FM Demodulator Circuit Module

This is a circuit about PLL system that can be used to implement an FM demodulator. Since the VCO output tracks the FM signal, and the VCO input voltage is proportional to the VCO output frequency, then the VCO input will be equal to the demodulated signal. This circuit is based on phase comparator and VCO. This is the figure of the circuit.


For this example, an FM signal consisting of a 10-kHz carrier frequency was modulated by a 400-Hz audio signal. The schematic diagram shows the connections of the CD4046B as an FM demodulator. The total FM signal amplitude is 500 mV, therefore, the signal must be ac coupled to the signal input (terminal 14). Phase comparator I is used for this application because a PLL system with a center frequency equal to the FM carrier frequency is needed. Phase comparator I lends itself to this application also because of its high signal-input-noise-rejection characteristics.