Design Project: Audio Media-Based Signal Generator

There are other ways to obtain good audio tracks, including recording the output of another signal generator. I have had such good success with the computer method, though, I can’t imagine that recording an analog source - no matter how good that source may be - would do much better.

Incidentally, the program I use is a Linux application called sox. It is a general-purpose sound file converter utility that also happens to have a “synthesizer” mode where it can generate audio tracks. Using this utility, I created twenty sine-wave tracks and then burnt them to a CD-R, where I could then play the tracks using a cheap ($17.00, 2004 U.S. currency) CD-audio player. I found the best wave quality to be when the player’s “anti-skip” mode was turned off.

Of course, this circuit could have been built with a “split” supply of V/Gnd/-V, but it is much easier to find or build a simple “single” power supply!

Theoretically, the op-amp should be able to handle the “handoff” between the two transistors even with no bias voltage, but since no op-amp has an infinite slew rate, there will be some crossover distortion under load (such as when driving am 8 Ω speaker). Placing a bit of DC bias voltage between the two transistor bases helps push them closer to ideal class-B operation, giving the op-amp an easier time of managing the crossover periods.