Continuously changing the distance between the palm of the hand and the antenna, the contractor thereby continuously – variable capacitive parameters castorocauda upper circuit on the oscillator circuit. This changes the frequency of the beating, and the tool extracted sounds of different pitch. If the result of manipulation by the performer, the frequency of oscillations at the output of the first RF generator varies, say, from 90 to 100 kHz, the musical range of theremin will lie in the interval from 0 to 10 000 Hz.
So, the performance of music on the theremin is to move one or both hands near the antenna of the instrument. To get a more smooth change of the pitch, the palm, monr keep stationary, and all actions produce only the fingers. In any case, in order to see such a musical instrument and master the technique it required good training and of course hearing.
Over 70 years of creative activities of L. S. theremin created lots of different versions of their AMY, and not less original. For example, one of his creations — terpsitone — electronic musical instrument, made in the form of a flat platform. Getting on it and making various movements, as if in a bizarre dance, the musician may execute at such an exotic instrument any product.
Interestingly, on the basis of the theremin was created and such “non-musical” devices, such as security devices for industrial buildings, warehouses, safes. Such a device was even guarding one of the halls of the Leningrad Hermitage. Developed by L. S. Termen electronic “watchman”, as it AMY, reacted to the change of the pattern of the electric field near the protected object and in case of unusual filed alarm.
But back to the musical abilities of the theremin. With the principles laid down in this tool, we have already met. Now it’s time to proceed to their practical implementation.
The theremin, which we offer, is assembled with just two logic chips, easy to establish and does not require hard to find parts. Of course, such a device far from a professional tool, but nevertheless, collecting it, you have to practice to get acquainted with the design, principle of operation and equipment performance of music on the theremin.
The first generator is assembled on the logical elements 2I-NOT DD1.1 and DD1.2 chips of DD1 (Fig. 2) and the second on the elements DD2.1 and DD2.2 IC DD2. Inverters DD1.3 and DD2.3 perform the role of decoupling devices for preventing mutual influence of the oscillators on each other. As a mixer used logic element DD2.4. Low-frequency amplifier assembled on the transistor VT1 by the scheme of the electronic key. Resistor R6 limits the base current of the transistor, and R7 is used to adjust the volume of the dynamic head of BA1. Capacitors C4—C6 and resistors R4, R5 form a low-pass filter, which excludes the mutual influence of the oscillators on each other through a supply chain. The device is powered by battery GB1 voltage of 9 V.
Both high-frequency generator assembled according to the schemes of asymmetrical multivibrators, with which you are already familiar (see “M-K”, 1990, № 1, “Six projects a single IMS”). Resistors R1, R3 and the capacitor C2 form customizados circuit of the first generator, a, R2 and C3— the same circuit of the second oscillator. Trimmer resistor R1 is necessary to “align” operating frequencies of both generators. Antenna WA1 is connected to the tool through the isolation capacitor C1.
Elements of the theremin are placed on a circuit Board with a size of 50X30 mm, made of foil Micarta or fiberglass with a thickness of 1-2 mm (Fig. 3).
Fig. 3. Circuit Board tool with the layout of the elements.
For the musical instrument will fit the following details. Transistor — КТ602АМ (BM) or КТ815, КТ817, КТ819 with any alphabetic index. Electrolytic capacitors C4—C6 of the brand K53, and the rest — ceramic compact, for example, KM5, КМ6. Fixed resistors — VS, MLT, OMLT, C2-23, C2-33 with a power of 0.125 W, trimmer — CP3-1B, JS4-1B, AC — type, SPO-0,25, SPO-0,5, JS1, JS2. Dynamic head — 0.5 GDS-2 or any other power 0.1—0.5 W with coil resistance of 4-8 Ohms. Toggle switch — small, brand VSD, MT1, МТД1. The battery “Corundum” or six-disc battery voltage of 1.5 V (for example, STS-30).
Details of the theremin housed in a metal enclosure of a suitable size. If this is not found, you can use any plastic box, pre-paste over it from within a foil. The metal body or foil is necessary to electrically connect a common wire feeding tool. The antenna is a copper or aluminum rod Ø 2-4 mm and a length of 25-40 mm is installed on the front panel of the case in a rubber or plastic insulator (Fig. 4). In addition, on the front panel are the on / off toggle switch power supply, variable resistor R7, is provided with a decorative handle, and dynamic head; diffuser “dynamics” is covered with a thin colored cloth. On the side wall of the shell — hole under the engine trimmer R1. Wiring connections are made of thin stranded wires in isolation.
Fig. 4. The appearance of the theremin.
At the correct installation and serviceable details the tool starts working immediately after power on. Setting it down in a zero beat frequency generators. If after power-up sound sound drivers not then need to setup disappears. If the sound appeared, rotating engine trimmer, until his disappearance. After that, the theremin is ready for operation.
It may happen that the sound of AMY will be unstable. In this case, perform the melody with one hand producing manipulations near the antenna, and the second touching metal parts of the housing. If you used a plastic box, covered the inside with foil, on the front panel, you must install a special metal plate about the size of 20X20 mm connecting the common wire power supply.
…The theremin was the world’s first musical instrument. Over the past decade created a lot of new AMY, what is easy to see, looking, for example, to equip a modern rock band. The electronic organ, electric guitar, electroman, electronic drum set is a list of musical instruments with the prefix “electro”, you can continue. Some of them we will tell in the next releases.
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