Vermes
Advanced Member level 4
This is a design of a simple stereo preamplifier equipped with tone control. Bass, treble and volume control can be done using double rotating potentiometers. The device is small, has low power consumption and is very cheap construction. It uses potentiometers, four popular transistors BC547B and few discrete components. The system can operate with any amplifier. It can also supply that preamplifier with voltage of 20-30V because there is a voltage stabilizer on the board. The maximum voltage is connected with the acceptable input voltage of the stabilizer and it should not be exceeded. When higher voltages are available from the supply of the power amplifier, an additional stabilizer like LM317 with a greater acceptable input voltage can be used. It would initially decrease the supply voltage of the preamplifier for e.g. approximately 25V. Indstead of stabilizer7818 you can use a smaller version 78L18, because its power consumption should not exceed 20mA.
Schematic:
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Link to original thread (useful attachment) - Przedwzmacniacz stereofoniczny z regulacją tonów