Double Sound Tremolo, Amaterske Radio, October 2004 🇨🇿

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modman
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Amaterske Radio 2004-10 Double Tremolo.pdf
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In Czech, but here is a rough translation from Google:
A tremolo is a circuit that periodically changes the level of a passing signal.
In this case, it is supplemented by a two-position switch, which allows the signal to be corrected by frequency.

Description
The wiring diagram of the tremolo is shown in Fig. 1. The operational amplifier IC1A is connected behind the input connector K1. Its gain is given by the ratio of resistors R2 / R1, ie about 5. A resistor divider R3 / vactrol is connected to the output of IC1A. The resistance of vactrol IC2A is dependent on the current of the excitation LED (IC2B). This is a maximum of 40 mA. At maximum current, the resistance of vactrol is about 1.5 kohms. Depending on the type used, the data given applies to the VTL5C3 version. Behind the resistive divider is the second operational amplifier IC1B. Use switch S1 to select a clear or corrected frequency response (sound).
The tremolo modulation frequency is controlled by an oscillator consisting of an IC3 circuit. Potentiometer P1 determines the modulation frequency and potentiometer P2 its depth. The vactrol LED is excited by a pair of transistors in the Darlington circuit T1 and T2. The tremolo plate is supplied with a symmetrical supply voltage of ± 9 to ± 15V

Building
The tremolo circuit is made on a double-sided printed circuit board with a size of dimensions 62 x 46 mm. The layout of the components on the printed circuit board is on Fig. 7, side board pattern components (TOP) is in Fig. 2, from the side of the joint (BOTTOM) is in Fig. 3. The connection does not contain any adjustment elements, so it should work on the first try when working carefully.
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