# Vibrato audio effect circuit [closed]

I would like to build a circuit that adds a "vibrato" audio effect to a simple sine wave input.

Sample audio clip from Wikipedia: Vibrato, Sound Frequency 500Hz, Frequency Modulation 50Hz - Vibrato Frequency 6 Hz https://upload.wikimedia.org/wikipedia/commons/e/e7/Frequenzmodulation.ogg

This sample effect is exactly what I want to create. I already have a circuit that generates a sine wave, and I can easily generate a 50 Hz frequency modulator. I'm just unsure of how to create a circuit that would provide that 6Hz vibrato effect and combine everything together to get the desired sound.

Does anyone have any ideas of things I can try to replicate the sample audio with the effect?

Thanks

• Please clarify how you designed sine wave generator (it may define design of the vibrato circuit/algorithm), and what you mean with vibrato as it may involve regular change of frequency and/or amplitude. – Anonymous Mar 10 '17 at 20:46
• Well it sounds like every 6 seconds the sine wave goes from 475Hz to 525Hz and back, if you're creating this tone digitally using a DAC, the solution is trivial since you can do it in software. – Kent Altobelli Jul 15 at 22:46
• You want to frequency modulate the 500Hz tone by 50Hz at 6 times per second. You did not show the schematic of your 500Hz oscillator for us to see if it is possible to modulate its frequency. – Audioguru Jul 16 at 2:21

At first glance this could have been easy if you were doing a tremolo. The vibrato on the other hand is quite hard to achieve.

Have you looked already at some guitar pedal implementation of the system such as the BOSS VB-2. It shows the building blocks of what is required for this to work.

My understanding it that you need an oscillating signal with its Rate and Amplitude (Depth) (IC5, IC4, IC3) to control the frequency shift introduced to the input signal by IC2.

The frequency shift is obtain by modulating the length of a delay line, which thanks to Doppler effects introduces a frequency shift (IC2 is a delay line), imagine turning the time knob of your delay pedal, you get those stretching/compressing of the signal which changes the pitch.

Do this in a sinusoidal fashion and you get a vibrato.

Both clean and wet signals are then added/filtered together by IC1 to get your final signal (clean on the non-inverting input, wet on the inverting input)

There is also a lot of filtering/amplifying that is out of the scope of my understanding. Also the rise time circuitry I don't really understand its fonctionnality.

Try to understand the basics of the delay line modulation, the rest is application specific.

I and Q modulators can be used; I've used them to generate Minimum Shift Keying for GSM cellphone signaling; the 2 GSM signals/baud/symbols are Frequency Shift Keyed/modulated.