Test Preparation

If you have not already installed PureData on your computer, do so first.

Items needed:

1. A CD player with a line output. Don't use a headphone output. (A CD player makes a simple substitute for a signal function generator. If you have a signal function generator, you can use that instead.)
2. An audio cable running from the CD player's line output to the input of your computer's sound card.
3. An audio CD with test signals. Here's how to make the CD.
4. A printout of the log sheet.
5. Attenuator (optional) to match the CD player output signal level to the sound card microphone input.

The reason for using an external CD player, rather than just replaying the wave files from within the computer, is that the computer's sound card will affect the signal also on playback. A sound played internally does not pass through the sound card's analog-to-digital converter, which is one of the components we are testing. By re-recording from an external source we can assess the quality of the analog input.

The reasons for using a line output rather than a headphone output is that (a) the line output has a fixed output level, (b) headphone outputs often have "sound enhancement" options with bass boost and/or spatial effects, (c) the small internal power amplifier for the headphones is often of questionable quality.