Squarewave Generator

In absence of a known good signal generator, the parallel port present on most standard PCs will present a usable substitute.

This program will output a squarewave by toggling the state of an output bit in the parallel port.   The parallel port is only capable of outputting DC, thus the signal is guaranteed to be perfectly square.   Click here to download program.

The program runs on any 32-bit distribution of windows, with the included MMP driver.

To utilize it, build a Parallel Port to RCA adapter according to this very simple schematic:

It's really that simple. It produces a perfect squarewave amplitude-wise, but due to windows timing limitations,
there will be timing jitter. Nevertheless, for our purposes, the signal is plenty good enough.

Feed the RCA to your sound card, and try a 30 Hz squarewave.

DC-straight path (simulated)

If your signal looks like the above image, congratulations! You have a DC straight sound card.

However, chances are, it will look more like this:

If so, please continue reading this page about Tilt.