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In recent years, following CD's introduction, vinyl recordings are almost disappeared. Nevertheless, a phono preamplifier is still useful for listening old vinyl discs from a well preserved collection.... [read more]

Other one unit of graphic EQ. five bands. The basic difference with the other circuits is, that I use instead of IC, transistor and the power supply, go up in +/- 24V DC, ensuring low distortion and bigger margins of overloading. With switch S1, we can isolate the EQ. inside or except operation, leaving the musical signal to pass without no alteration.... [read more]

Many people experienced sleeping well in natural surroundings, into a tent or a wooden hut. This fact is due not only to the healthy atmosphere but also from our unconscious ability to perceive natural Earth's magnetic-fields. The circuit generates this type of Geo-magnetic-fields and lets us perceive them: in this manner our brain is surrounded by an ideal environment for a sound sleep.... [read more]

Here is a simple triangle/squarewave generator using a common 1458 dual op-amp that can be used from very low frequencies to about 10 Khz. The time interval for one half cycle is about R*C and the outputs will supply about 10 milliamps of current. Triangle amplitude can be altered by adjusting the 47K resistor, and waveform offset can be removed by adding a capacitor in series with the output.... [read more]

All miniature electronic devices operate off batteries. Some of them need higher than the standard battery voltages to operate efficiently. If the battery of that specific voltage is unavailable, we are forced to connect additional cells in series to step up the DC voltage. Thus, the true meaning of miniaturisation is lost. A simple way to overcome this problem is to employ a voltage doubler, if the device under consideration can operate at a small current.... [read more]

With this circuit we can amplification selectively the high signal of picture frequencies [Video] with result bigger clarity than this. The circuit should be placed between a Video unit and the reception Scart or the plug Video input of television receiver.... [read more]