MIDI controlled vibrato/tremolo effect

[martinvicanek]

Hi gang, this little device applies a vibrato or tremolo effect to an audio stream. Nothing sensational really. I use it for postprocessing vocals or solo instruments, controlling the amount of the effect with the mod wheel of my MIDI controller.

[adamszabo]

Really simple and effective, thanks!

[Spogg]

Very nice Martin and thanks for sharing.

I like the fact that the vibrato depth is in semitones, presumably so the centre frequency remains stable for any depth setting.

One thing…
The module hung with a bang when I set the frequency to zero, so I just made the minimum 0.01 Hz. Some oscillators just stop at zero Hz so it gave me a shock (had the speakers at high volume ).

Cheers

Spogg

[martinvicanek]

Oops - thanks for pointing that out, Spogg! The problem is that the lower the (vibrato) frequency, the longer the necessary delay line to achieve a given vibrato depth. For zero frequency the delay would be infinite, which is not feasible. So yes, the knob range should not go down to zero frequency.

Actually the vibrato range is not strictly symmetrical in terms of semitones (it is in terms of Hz), but the effect is not very strong for moderate vibrato ranges.

[trogluddite]

Thanks, Martin! The quadrature osc for the LFO works really nicely - a little hint of Leslie Cab for so little CPU. I also rather enjoyed "reverse-engineering" the stereo optimisation in the delay ASM - the shuffled current/previous sample storage is a very neat technique that I must try to remember!