Creating voice modifier from scratch

[SaraBMB]

Hello everyone,
I am a beginner and I have zero knowledge about voice modifiers, yet I want to make one!
It is a mini project for a digital hardware course I am studying, but they only taught us the very basics. Only requirement is that it should work using AC and that it does not have readymade chips.

So, I want first to know, is creating such circuit simple or not?
If yes, what are the things I will need and how can it be made?

Thank you, you will be such a big help.

 

[canadaelk]

Google "vocoder schematic". To find one without dedicated ICs you will have to go to something pre 1980. E

 

[WTP Pepper]

You do not say how you want the device to change the voice.
Pitch changing without dedicated chips or specific hardware is complex.
Use (and Google) a (diode) ring modulator. This is what was used for the Dalek's voice in Dr Who - a UK SciFi series from the 60's/70's/80's.
This can be done with a few transistors.

For basic pitch conversion, an analogue switch (CD4016) can be used to chop the audio at a frequency say 3KHz and a bit of clever filtering. Not a simple task for a beginner as there are biasing and pre/post-filtering issues.

 

[SaraBMB]

Canadaelk, yeah I know that I'll have to use a very old model, I don't mind that. Thank you.

WTP, I did not say how I want it to change the voice because I don't need anything complex or great, I am okay with any kind of modification in the voice.
So an analog switch, I see. I have no idea about how to filter though..

Isn't there any simple way of making it? Because if it's that complex, then I guess I should choose another project idea.

 

[dougy83]

I'm not sure how complex or simple you can handle, but here's a version of the [squarewave] mixer (ref https://www.diyaudio.com/forums/instruments-amps/107954-ring-mod-design-comments-welcomed.html).

 

[WTP Pepper]

Without building it and testing it, Dougy's cct looks good. It effectively mixes the voice with a fixed frequency thus changing it's pitch.
Each block can be easily defined to understand what's going on. However that's your job Sara to show your tutors you understand the principles.

 

[SaraBMB]

Dougy,
Thank you very much!!! This circuit is extremly helpful!
It makes it waye asier for me. Though, can you please further explain how to implement it? Also, I can't tell all the needed components from the diagram only; tnere are symbols that i didn't recognize. May you please tell me the components needed to do that circuit?

WTP,
Yeah it looks great! I am having high hopes that it will work amazingly.
And it's not exactly a thing that I studied so I explain; we didn't take anything about voice modifiers. The project requires any simple circuit that works on AC. Making voice modifier is my own idea that I studied nothing about; I chose it because I think it's intersting. That's why I came here in this form; to seek help from you experts about the principles and methods to make such a circuit.

 

[Mike odom]

the write up at the bottom of the circuit is wrong. It states that IC1a is the 3kHz low pass, but that is IC1b.

 

[canadaelk]

That circuit does not change the pitch, it chops the signal input thus the name: Vader Voice.
To change the pitch you need a rather complicated circuit as is used in feedback eliminators (analog computers or DSP).
Phase shifters, fuzz, tremolo and so on are not that complicated to construct. E

 

[audioguru]

I made a voice scrambler with an MC1496 balanced modulator/demodulator IC and some switched capacitor lowpass filter ICs. The circuit was fairly simple.
It used single-sideband suppressed carrier and reversed the audio frequencies so that low frequencies became high and high frequencies became low. Speech was completely unintelligible. A similar circuit demodulated it and its output sounded completely normal.

The circuit could be changed a little and used as a voice frequency shifter to make a low pitched man's voice sound like a high pitched little girl's voice or vise-versa.

 

[dougy83]

Dougy,
Thank you very much!!! This circuit is extremly helpful!
It makes it waye asier for me. Though, can you please further explain how to implement it? Also, I can't tell all the needed components from the diagram only; tnere are symbols that i didn't recognize. May you please tell me the components needed to do that circuit?

I have no idea what it sounds like, but it will certainly modify the speech.
IC1 LM358 dual op amp (IC1a and IC1b are in the same package)
IC2 CD4066 analogue switch
IC3 7555 or 555 timer IC
IC4 LM386 audio amplifier
MIC electret microphone
9V battery
There's a speaker at the far right
Pretty much everything else is either a resistor or capacitor (& one switch).

 

[WTP Pepper]

That circuit does not change the pitch, it chops the signal input thus the name: Vader Voice.
To change the pitch you need a rather complicated circuit as is used in feedback eliminators (analog computers or DSP).
Phase shifters, fuzz, tremolo and so on are not that complicated to construct. E

Technically you are wrong. Chopping a signal with an on/off signal is equivalent to mutiplying a signal by either 1 (signal) or 0 (nothing). If you do the maths, that imposes a frequency shift. It's a common technique used in sub band sampling and similar to how superhet receivers work.

2 sin A cos B = sin (A + B) + sin (A - B) It produces a sum and difference. You cancel out either with the right type of filter and you get a deep voice or a high pitched one. Just like you get an upper side band and a lower side band on a receiver.

Fuzz and tremelo are not frequency shifters. The first adds distortion to the fundamental and albeit produce harmonics, it does not move the fundamental frequency, a tremelo effect is a delay effect.

 

[audioguru]

a tremelo effect is a delay effect.

No.
Tremolo in music is amplitude fluctuations, not a delay. Vibrato is frequency fluctuations.

 

[SaraBMB]

Hello everyone,
I had some urgent matters that made me unable to continue with the project at that time, that's why I have been away for a month now. Thank you all for your help, I am back now to continue my project.

 

[SaraBMB]

I have no idea what it sounds like, but it will certainly modify the speech.
IC1 LM358 dual op amp (IC1a and IC1b are in the same package)
IC2 CD4066 analogue switch
IC3 7555 or 555 timer IC
IC4 LM386 audio amplifier
MIC electret microphone
9V battery
There's a speaker at the far right
Pretty much everything else is either a resistor or capacitor (& one switch).

Hello Dougy,
Thank you for sorting the components for me! However, I think I have an issue. It is required in the project to use AC not DC, so I cannot use a battery. Do you think this circuit can be modified to work on AC?

 

[SaraBMB]

I made a voice scrambler with an MC1496 balanced modulator/demodulator IC and some switched capacitor lowpass filter ICs. The circuit was fairly simple.
It used single-sideband suppressed carrier and reversed the audio frequencies so that low frequencies became high and high frequencies became low. Speech was completely unintelligible. A similar circuit demodulated it and its output sounded completely normal.

The circuit could be changed a little and used as a voice frequency shifter to make a low pitched man's voice sound like a high pitched little girl's voice or vise-versa.

Audioguru,
The circuit you made seems good and simple, and does exactly what I need! Can you please tell me more about how you did it exactly and what are all the components you used?

 

[dougy83]

Hello Dougy,
Thank you for sorting the components for me! However, I think I have an issue. It is required in the project to use AC not DC, so I cannot use a battery. Do you think this circuit can be modified to work on AC?

You can convert from AC to DC using a rectifier and capacitor, as seen in the following diagram.

You may have some hum introduced from the AC. D1 is a bridge rectifier, which can be a single device, or formed using four individual diodes.

 

[audioguru]

Audioguru,
The circuit you made seems good and simple, and does exactly what I need! Can you please tell me more about how you did it exactly and what are all the components you used?

Today somebody else (in your class?) also wanted to amplitude-modulate and frequency-modulate voices. I looked at the availability of the MC1496 in Digikey (surface-mount only) and Newark (highest quality through hole and ordinary surface mount). The circuit is in its datasheet.