|MadSci Network: Engineering|
Here's a magazine article. (I don't have this issue, so I can't verify if it's correct)
Radio Electronics (magazine) January 1993Here is a schematic which uses a Holtek HT8950 voice-changer chip.
"Build Your Own Digital Voice Changer"
http://electronickits.com/kit/complete/surv/ck211.htmOne very simple method of changing your voice is shown on this webpage below, but it can only make your voice LOWER in frequency:
SIMPLE BAT DETECTORIf you want to do it yourself, one way to change your voice is to pass it through a "balanced modulator" circuit such as an ANALOG MULTIPLIER chip (for example the Motorla MC1494 chip.) You feed a sine wave into one input, feed the audio signal into the other input, and the output is a weirdly scrambled voice. (multiplying a voice spectrum by a sine wave actually gives you a "sum" spectrum where the voice frequency is higher, and a "difference" spectrum where the voice frequencies are both lower and also backwards!) Tune the sine wave frequency to change how the voice sounds.
A true "pitch bender" circuit uses two analog
multipliers, two separate sinewave oscillators,
and various filters and op-amps. Each sinewave
signal is sent to one input of
each multipler. The original audio is sent to the
other input of the first
multiplier, which creates "sum and difference"
frequencies on its output. A low-pass filter then removes
the "sum" frequencies. The result is sent
to the second multipler, which creates DIFFERENT
sum/difference frequences because its sinewave
oscillator is not set the same as the first one.
A low-pass filter then removes the "sum"
frequencies, and the output result is normal audio.
But if the frequencies of the two sinewave
oscillators are not set exactly the same, then
the audio output will
be shifted in frequency. You can make guys sound
like gals and vice versa.
CIRCUIT BENDERS PAGE
Try the links in the MadSci Library for more information on Engineering.