I was asked about my vocoder projekt. Yes, it has been a long time since I wrote about it. And yes, I will publish the complete data for my vocoder project. Uhhhh… just looked up what I have published so far. It dates back to end 2014 with a lot off t.b.d statements. I finished the vocoder display module over a year ago. I need to update the site.

Vocoder Display Front

The vocoder synthesize part is tested and a first prototype with six channels is tested and running.

Vocoder Synthesizer VCA Testboard

BP for Vocoder Synthesizer

Testboards for Vocoder Synthesizer 3×2 Channels

I have the PCB’s for all 24 channels and the backplane laying around here. Needs to be stuffed and faceplate.

Final PCB for Vocoder Synthesizer

The vocoder input part is on stripboard and tested. Needs PCB and faceplate. The vocoder voiced unvoiced detection needs decision which way to go. Extra filters or using the available outputs from the vocoder analyzer and weighing the voltages. I think the later is the easier way to go in the moment.

Jürgen Haible’s vocoder PCB is available again. The guy who made it possible visited me some weeks ago and we had some talk about vocoder and other stuff. I wanted a more flexible account then Jürgen with his one big PCB. With my design you can start with eight channels and then go up to 16 and 24. And very important for me you can change filters. So you can use different characteristic for the filters and different frequency settings.

While waiting for the revised VCO PCB and still working on the details with swapping OpAmps in and out and adjusting some resistors, it’s time to talk about a bigger project. Let’s talk VOCODER!

Building a vocoder was a dream of mine for many years. There where some diy vocoders around in the late seventieth: Elektor Vocoder (10 Channel), ELRAD Vocoder (14 Channel) and ETI Vocoder (10 channels). May be some more I didn’t know. The ELRAD Vocoder used one big PCB for all filters, the Elektor Vocoder used one PCB for each filter and was build in an 19” Zoll Rack.

In 2011 Jürgen Haible designed his 20 Channel Vocoder on one big PCB. Due to his early death only a few PCB were sold. I have had only occasional contact with him. But it was inspiring to talk “synthesizers” with him. I’ll miss him. I will use some of his filter design partly in my vocoder.

Now I heave the time and the means to design and build my own vocoder. First thought was to go the Elektor way: one channel, one PCB. Having only one big PCB seems to unflexible for me. But I want to use and explore different filter topology and frequency distributions as well. So I decided to split my vocoder in functional blocks instead of channels and make the filters pluggable. The functional blocks are divided further in 8 channels per block. So I have the flexibility of exchangeable filters and not to big PCB’s in the blocks of eight.

Block Diagram

So far I have the analyzer part nearly completed, the display part completed, the synthesizer part with preliminary PCB’s running on six channels and the input stage in early prototype mode with stripboard running.

Inside analyzer

CV Display