This electronic doorbell is essentially a small WAV file player based around an ATmega328P. When a guest presses the bellpush the device is activated and plays out a short WAV file using its... Read more
This square wave generator and tester is based on audio amplifier chip type TBA820M. It is presented as a design idea for further refinement and optimizing of component values by way of expe... Read more
The problem that this circuit is designed to solve appeared when the author was installing a new radio in his Audi A3. The new radio had four outputs for loudspeakers and a line-level output... Read more
The low dropout voltage regulators from the LM2931 series are not just useful for powering microcontroller systems — they can also act as a low-frequency (practically) random noise generator... Read more
This circuit is a revised version of the Audio Limiter published in the 2002 Summer Circuits edition, which is intended to limit the (possibly excessive) dynamic range of the audio signal fr... Read more
This circuit is inspired by an amplifier published in the ’60s that produced 8 watts a channel into 8 Ω and was based on AD161 and AD162 germanium (not ‘geranium’) power transistors. These,... Read more
The TDA7052A is a readily available amplifier chip (Farnell # 526198) that has a DC controlled volume input. Here, the IC is used as the variable gain amplifier in a guitar compressor, so th... Read more
The AC power line indicator presented here has a complete galvanic isolation from the grid. The indicator is an LED that lights up when a current flows, although the current can be measured... Read more
The compact circuit presented here is perfect for receiving the signals from pulsed fixed frequency transmitters. Chest straps from several well-known brands (Polar, Huger, Kettler, Crane, O... Read more
If you’re short of inputs on your amplifier, but it has an input for a magnetic pickup with RIAA correction, this very simple project will et you convert this into a high-level linear input,... Read more
