About Bitcrusher effects.
A Bitcrusher is a low-fidelity effect used to emulate the distortion introduced by older samplers, and wavetable synthesizers. They work by reducing the sampling rate (the frequency at which the audio signal is sampled, or bit-rate), or reducing the bit size of the samples (the number of bits used to digitally represent the amplitude of the audio waveform). These can reductions can be used independently or together. A Bitcrusher will by virtue of the way it operates introduce digital noise and aliasing into the audio, this is deliberate, as this is emulating the sound of the older low resolution audio samplers and wavetable synthesizers.
Bitcrusher options in SynthEdit:
There are currently three options;
1) A third party module by Elena Novaretti in her ED DSP module pack, the
ED Crusher which (personal opinion) I think is currently the better option. This has the edge on the community modules BitCrushers in that it allows reduction of both bit depth, and sampling rate together.
2) The BitReducer in the Community modules.
3) The BitCrusher in the Community modules.
A basic SynthEdit Bitcrusher design.
The 1 pole LP in the input is fixed at 15kHz, and is included to limit the input signal to prevent too high a frequency entering and causing un necessary aliasing or distortion. The sampling frequency (X Quantize) is controlled via the Volts to Float2 module, and the properties for this module are set to Volts DC (Fast), and an update rate of 10 Hz.
The amplitude sampling (Y Quantize) setting is controlled via a RoySwitchL(Int), and a set of Integer fixed values (4, 8, 16, 32) selectable via a drop down list.
The LP filter in the output is not an attempt to reduce aliasing (once you introduce aliasing you can’t get rid of it) as it’s a part of what we are re-creating, it’s there to reduce the high frequency output to get closer to the low fi sound of old samplers and wavetable synthesizers.
Note: All Bitcrushers produce noise and aliasing because you are reducing the sampling rates, and thus decreasing the Nyquist frequency.
Note: You can put chords through a bitcrusher, but it sounds much better with single notes. Once you start putting chords, or harmonically complex signals through this effect the resulting audio quickly becomes a noisy mess (very much like using an ordinary fuzz box).
If you’re using this effect in a synthesizer plugin to recreate the sound of a vintage 8 bit wavetable synthesizer it’s much better to have one bitcrusher per voice, than one bitcrusher used on all the voices together.
Will oversampling improve the sound from a bitcrusher? In short, no. You will actually be wasting CPU resources on something that will not help create the lo-fi sound that’s intended. You won’t reduce the noise or aliasing noticeably…and I have to ask why you want to increase the quality when the aim is to create a vintage lo-fi sound?
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