Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9424179 | Journal of Neuroscience Methods | 2005 | 5 Pages |
Abstract
The design objective was to develop an inexpensive digital to analog (D/A) converter for use in vision science. Soundcards are hardware units that can be integral or can be added to a computer to add sound capability. A soundcard contains D/A converters designed to work in the audio frequency range, typically 20-20,000Â Hz. Soundcard outputs are high-pass filtered and thus do not convey sub-audio frequency or dc information. It is possible to circumvent this design feature by programming the desired output waveform as an amplitude modulation of a high frequency carrier, and then demodulating the soundcard output. The circuit, using a 20Â kHz carrier, provides precise D/A conversion for the frequency range relevant for vision experiments, dc to 100Â Hz, using inexpensive readily available components. The specific application was for 8 channels of D/A conversion using a Macintosh computer running under OS X. The software needed to program stimuli was created using CoreAudio, a library for programming sounds in OS X. Using soundcards on other platforms would not be a problem, as long as there exists a low level library that would enable the wave table to be filled.
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Authors
Marco J. H. Puts, Joel Pokorny, Jules Quinlan, Linda Glennie,