Low-distortion DDS Signal Generator

摘要

All the PCBs to build this project are already available from the PE PCB Service. As we mentioned earlier, they were also used in the DSP Active Crossover/Parametric Equaliser project. They are coded 01106192-01106196. Many of the parts are SMDs, some of them fine-pitched, so this is not an ideal project for beginners. Building this will provide you with a test instrument with excellent performance, that can carry out many important audio tests, especially for Hi-Fi. You could even combine this Low-distortion DDS Signal Generator with a high-quality ADC connected to a computer, feeding into spectrum analysis software, as an audio analyser capable of measuring distortion in devices like amplifiers, preamplifiers and filters, down to very low levels. It can also be used in conjunction with our High-resolution Audio Millivoltmeter project, published in the October 2020 issue of PE, for making signal-to-noise ratio measurements. That would be a great way to make and save frequency response plots, with the Low-distortion DDS Signal Generator in sweep mode and the High-resolution Audio Millivoltmeter connected to a USB port, for logging the results, which could then be fed to a plotting program.