Visual Analyser Project ( current v. 25 Silvia edition  )

Visual Analyser for Windows

A brief introduction

 This introduction was written when VA was only five years old. I am leaving it in its original form to convey the initial spirit that motivated me to create VA.

By Alfredo Accattatis

Many people cannot afford to buy an expensive oscilloscope or spectrum analyzer, or they may simply not want to invest in a tool they will only use occasionally. However, many enthusiasts enjoy building and testing audio amplifiers or other simple circuits (oscillators, filters, etc.), or they may need to monitor specific signals (e.g., sensor outputs) within the audio frequency range. For instance, many musicians require a spectrum analyzer with an embedded octave band analysis tool.

 A good sound card may be all the hardware needed for this purpose, along with a PC—an investment many already possess at no additional cost. A modern sound card with a sampling rate of 96 kHz or even 192 kHz can handle signals up to 96 kHz (well beyond the typical audio range), effectively turning Visual Analyser (VA) into a powerful suite of instruments for general electronics and other applications. 

VA is invaluable wherever an oscilloscope, spectrum analyzer, frequency meter, voltmeter, function generator, or even a THD (Total Harmonic Distortion) meter is needed. For example, when tuning a class B power amplifier, you may need a spectrum analyzer or a THD meter to minimize crossover distortion. The concept of using a PC’s sound card for such tasks is not new (there are many programs similar to VA), but my aim was to create a tool specifically designed for audio circuit analysis for electronics enthusiasts. 

I believe VA is probably less “flashy” than other software (i.e., fewer windows and decorative elements) but is rich in substance and original features. I have been working on VA for five years. It is a continuously evolving software project, with frequent updates and new features ready for download. One of VA’s unparalleled capabilities is its real-time digital-to-analog (D/A) conversion for the oscilloscope function, a feature that is often misunderstood. Consider using a standard 44.1 kHz sampling frequency with 16-bit resolution (resolution is not critical for the following discussion). 

 Most similar programs simply plot raw points on the screen, making it difficult to analyze signals above 3,000–5,000 Hz due to the limited number of points. For example, consider a 20 kHz sinusoidal signal, which would only have approximately two points per complete cycle. While the Nyquist theorem states that this is sufficient for reconstructing the signal (i.e., calculating all points between the two plotted points), standard software often connects these points with straight lines, resulting in a waveform that resembles a triangle rather than a true sine wave. By enabling VA’s “full D/A” function, applying a 15–20 kHz sinusoidal signal (e.g., generated using VA’s built-in waveform generator), and using the “Time division” control (mS/d) for the selected channel, you can observe a perfectly reconstructed waveform with all original points, not just two per cycle. Another powerful feature of VA is its waveform generator, which uses band-limited algorithms to prevent aliasing during waveform generation. Aliasing can render generated waveforms completely unusable. 

 VA is also easy to use. Run the installer and install VA in a preferred directory. Select the input source through Windows’ “Volume Control” or, ideally, through VA’s “input source” listbox (located in the upper right corner of the command bar under the main window caption). Click the “on” button (also on the command bar) to activate the tool. Most options can be configured directly from the main window, while all remaining commands and setup options are accessible via the “settings” window, which can be opened from the command bar using the “settings” button. English help documentation is available for each window but is still under development.

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Send an e-mail to  alfredo[at]accattatis.org for questions and/or suggestions about the web site. The webmaster is Alfredo Accattatis.
Last modified: 03-nov-2024