MFOS 12 Channel Vocoder PCB

From MFOS - A 12 channel vocoder PCB!

This is for a PCB only, suitable for multiple formats.

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  • Built in White/Pink Noise Source
  • Built in Square/Pulse Oscillator
  • Mic/Line Inputs for Control and Audio
  • Good Dynamic Response To Voice Control
  • Reasonably Intelligible Speech Processing



A vocoder has got to be one of the coolest signal processors going. It allows you to impress vocal harmonic and dynamic characteristics onto other sound sources making them sound as if they are talking. This vocoder design works by using one lo-pass filter (100 Hz.), ten successively tuned band-pass filters (154, 208, 285, 395, 542, 720, 1013, 1495, 2000, 2546 Hz.) and one hi-pass filter (3330 Hz.) to separate the incomingcontrol signal into its harmonic constituents. For each band the control signal appearing at the output of its corresponding filter is full wave rectified and low pass filtered to obtain the control signal's envelope voltage. This signal is used to drive a VCA through which the channel's filtered audio is amplitude controlled. The whole circuit is described below but all I can say is that this thing is totally cool and I'm very happy with mine (I am somewhat biased).


User Modifications

I have a good feeling about this project. It's my hope that it becomes one of those that people enjoy building and it's perfect for people who enjoy modifying designs (see Vocoder Expansion and the Filter Design tab). If and when I ever modify mine (who knows, winter's coming...) I'll document it completely in a new sub-tab entitled "Modifications". Any experimenters willing to share schematics/photos of discovered improvements or modifications are invited to let me know at info@musicfromouter...(you know the rest).com. Please include links to sound samples when you email so I can publish them along with the modification information. People will appreciate hearing what the mod results in. As a standard for at least one of the samples (and I suggest you provide several sample links) I propose using one of the sample vocal loops below so everyone knows what the voice control source material sounds like. I'll add the info (or links to it if you prefer) and sound sample links to the "Modifications" page with credit to you for having contributed the idea. Open source comes to vocoders!


Sample MP3s

I really hope you take the time to listen to the samples before embarking on this project. It is a fairly large investment in time and money and I want you to be happy with the results. I am looking forward to using mine in some of my upcoming musical projects and I really like it. The samples will give you a good idea of the speech intelligibility you can expect when used with a decent microphone and a keyboard. Your build will sound similar.

You should also know that a twelve channel vocoder is not going to sound like a DSP plugin or footpedal vocoder. So... before you get out your solder iron expecting one thing... listen to the samples. I love this vocoder and I think it's totally cool but it's kind of like my child by now so you can understand why. If you do build the project I have to say that the board soldered up very nicely and the vocoder worked prefectly after I tracked down one unsoldered resistor lead and calibrated the channel gains. Good soldering.


Specs & Downloads

Specs & Downloads

Manufacturer MFOS
Depth No
+12V No
-12V No
+5V No
Additional Resources


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