Build an analog vocoder

Step 6 Enjoy

Now just get down and mess around with your new vocoder. I had never played around with one of these and I am just about scratching the surface... This vocoder (with patch cables) will allow you to invert the spectrum or transpose it, (even use external CV from analog gear like sequencers).

Credits:
The design borrows ideas from several vocoder schematics on the net. Many of these vocoders used difficult to find parts and many more components. I used a filter calculator provided on the net by Okawa Electric Design (http://sim.okawa-denshi.jp/en/OPtazyuBakeisan.htm) to design the filter banks. Also, I borrowed the concept of only varying condensers on the filter from the Okita vocoder, this makes it very easy to make all the banks because they are identical except for 8 capacitors in each; making the voltage control patchable was borrowed from the Elekvoc. The voltage controlled amplifier is based on a circuit made available from Rene Schmitz.

Comments

[Pedro Freitas]

Hi! Excellent tuturial! I'm really hooked now. How do I trimm the trimmer pots comming out of the followers? And, how about the VCA trimmers, what sould I aim for? Thanks! Pedro

[planetone]

Good point Pedro... the VCA trimmers should be trimmed to eliminate dc offset at the output (you will not remove it entirely, but that is part of the reason for the condensers at the mixer inputs. As far as the trimmers on the follower, the aim is to get a range of about 0 - 10V on the CV signal -- more to the point, try to get a flat response from the bank. This means that the CV of each channel should reach the same level when the intensity of a "tuned" signal is applied (does this make sense?)... what I did was to feed white noise and later a sweeping sine wave and made sure all CV maxed at the same level (or as close as possible).

[Pedro Freitas]

Cool! That made perfect sense. Thanks! On to drawing PCBs :) ... Pedro

[sergiorodrig]

awesome dude !!!!! kick it old school