This circuit can be used for inductive pick-up elements and dynamic microphones Most soundcards have a ‘line’ input and one for an electret (condenser) microphone. To be able to connect an inductive tape-recorder head or a dynamic microphone, an add-on preamplifier is needed. Even in this day and age of integrated microelectronics, a transistorised circuit built from discrete part has a right of existence. The preamplifier described in this short article goes to show that it will be some time before discrete transistors are part of the silicon heritage. The preamplifier is suitable for use with a soundcard or the microphone input of a modem. As you will probably know, most sound-cards have input sockets for signals at line level (stereo), as well as one for a (mono) electret microphone. For the applications we have in mind, connecting-up an inductive pick-up element or a dynamic microphone, both inputs are in principle suitable, provided the source signal is amplified as required. The ...