Accentize has introduced PreFET, a freeware saturation plugin that uses machine learning to emulate a 70s tabletop cassette recorder’s transistor preamp.
PreFET uses an artificial neural network algorithm that has simulates the transistor preamp found in an audio cassette recorder from the 1970s. The plugin takes advantage of the same technology that was used for the PreTube (currently on sale for 47€), a premium tape saturation plugin from the same developer. Unlike the PreTube plugin, which emulates three different preamp models, PreFET focuses on a single transistor preamp model.
So, instead of using circuit modeling or wave-shaping (like most other saturation plugins), PreFET and PreTube utilize machine learning to “train” the neural network to match the behavior of the analog hardware as precisely as possible. This means that the algorithm responds dynamically to the input gain, and the user can control the amount of saturation that is applied to the signal. PreFET features an input gain control and a drive knob, as well as a bypass switch that turns off the processing.
PreFET supports mono and stereo channel processing. It can operate at four sample rate settings (44.1kHz, 48kHz, 96kHz, and 192kHz). The plugin sounds very good, and, based on a very brief test, I believe that it emulates a transistor preamp rather precisely. I liked how PreFET tames the volume peaks almost transparently at lower gain settings without introducing audible distortion. High-gain settings can also be useful if you’re looking for analog-style distortion.
The drawback here is PreFET’s high CPU usage. I see a consistent 19% CPU hit (on a single core) on my 6th gen i7 mobile CPU. This is decent for use on the master channel or for offline rendering, but it isn’t possible to use PreFET across the mix as a subtle saturation tool. Accentize claims that their plugins are optimized for low CPU consumption, and I do believe that the plugins are optimized, but using a lot of processing resources is simply the nature of neural networks.
You can download PreFET free of charge from the developer’s website. It comes as an EXE installer that will extract the necessary plugin files on your computer. The software is available in VST3, AU, and AAX plugin formats for 64-bit digital audio workstations on PC and Mac. The plugin doesn’t require manual activation but the developer states that PreFET will “send an anonymous machine ID to their server to automatically receive your free registration code.”
More info: PreFET (12.3 MB download size, EXE installer, 64-bit VST3/AU/AAX plugin format for Windows & macOS)