This paper describes the theoretical background and the source-code of a software plugin emulating a tube amplifier for electric guitars. The circuit 5E3 of the Fender Tweed Deluxe amplifier is used as the base for the amp model. Some circuit variants and a universal tone stack extend the tonal range of the original circuit. In contrast to existing comparable solutions, this plugin runs in real-time even on fanless tablets, with very low latency, and with plenty resources left for the obligatory IR-loader and an armada of additional guitar effects, if required. The sound quality and the playing experience is at least on par with existing solutions. The models for the tube stages are based on real tube circuits but are simplified as much as possible without sacrificing aspects relevant to sound and playing experience. The plugin format is JSFX. The JSFX script may be loaded into the VST3, AU or CLAP plugin YSFX provided by Joep Vanlier, or it can be directly used in the digital audio workstation REAPER by Cockos Inc. YSFX is available free of charge for Windows, MacOS and Linux.

The plugin “Blender” can blend or switch between two audio channels A and B. It is very useful to blend between two IR-loader plugins or to switch between two guitar amp plugins. The plugin has four input channels for two stereo inputs. You may restrict the number of input channels of the plugin to two input channels in your DAW. In this case the plugin will blend between the two mono inputs or between the left and right channel of a stereo input.

The plugin “360 ° Panner” implements a vector-rotation based panorama control. When panning hard right for example the original mono signal will appear on the right channel and the original side signal will appear on the left channel. The pan position can be modulated too. This way it is possible to create the illusion that a stereo signal is rotating 360 ° around the listener. You can hear this effect in the middle part of the Pink Floyd song “Poles Apart” where the orchestra seems to rotate slowly around you.

The plugin “Volume Wah” is an improved version of the plugin described in the authors paper “Wah-Wah Plugin”: A programmed GUI has been added. The signal processing is modular now by using the authors DSP block libraries. The parameter smoothing is improved. The frequency scaling is even more flexible. With its default settings the plugin emulates the famous VOX V847 Wah-Wah pedal. The plugin can act as volume pedal as well.

This paper describes the source-code of a Wah-Wah software-plugin in JSFX format. JSFX-plugins are simple text files which can be loaded into the ReaJS plugin by Cockos Inc.. ReaJS is a VST2 plugin and part of the popular (and free) ReaPlugs suite. A second-order digital state-variable filter as described in the authors previous GITEC contribution [1] is used to implement the Wah-Wah effect. The default filter parameters fit the famous Vox V847 Wah. However, the user may customize the filter parameters and arrive at his or her very personal Wah-Wah sound. The plugin can also operate as a volume pedal.

This paper provides an overview over all commonly used first- and second-order analog filter types and describes, step by step, the derivation of corresponding digital state-variable filters. The derived digital state-variable filters are bilinear-transformed versions of the analog filters. They are suitable for modulation of the filter parameters. Possible applications are e.g. wah-wah effects, emulations of voltage controlled filters of analog synthesizers, or dynamic equalizers.

The present article shows how the impedance of electromagnetic guitar pickups can be measured using a regular sound card in combination with a simple passive measurement adapter. If reduced accuracy is acceptable the pickup can even remain mounted on the guitar. The article also describes the automatic estimation of the parameters of an equivalent-circuit model for the pickup, as well as the calculation of the pickup’s frequency response. All associated steps and processes are implemented via a GUI driven script designated “Pickup Wizard”. It requires MATLAB® or GNU Octave as an interpreter. GNU Oc­tave (https://www.gnu.org/software/octave) is an open-source alternative to the well-known commercial software MATLAB®. The “Pickup Wizard” script is available free of charge from the GITEC homepage. Underlying theory is discussed in order to prove the validity of the process. Advice for putting together the measurement adaptor as well as a user manual for “Pickup Wizard” are provided for those who seek not to deep-dive into theory but simply want to measure and view the results.