Notice: Elektor March 2014 is processed for mailing to US, UK and ROW Members starting February 17, 2014 Small Audio Output Stage A small audio power amplifier with a modest ability but still good specifications is a handy circuit for a variety of audio applications. Just think of an active two-or three-way speaker system, in which the power amplifiers are incorporated in the box together with the power supply. The amplifier is based on a number of classic schematics with proven quality. The design is compact and offers space for your own extensions. Precision Adjustable DC Current Source An adjustable current source is a handy tool for testing diodes, zener diodes and LEDs to mention just a few parts. Provided it is sufficiently accurate, the instrument should also allow you to determine the brightness of an LED or to record the voltage-current characteristic of a zener diode. Our instrument has 20 measuring ranges of 10 nA to 20 mA and also has a built-in digital 3½-digit voltmeter with two ranges. Mini Breadboard Modules Many electronics designers use a breadboard to build a circuit, so they can experiment extensively. In doing this you often have to replicate the same sub circuits over and over again. That can be avoided by using a number of standard modules that fit on virtually any breadboard. This way you can create a power supply, a microcontroller, or a display, and easily add it to a circuit.