JH. Living Vocoder
20-Band Vocoder with 8-pole Filters
Finished PCB layout (RIMU screenshot)
The Filterbank funktion will have 3 modes:
1) On
The Filterbank will always be mixed with the vocoded sound, acording to how you set the Filterbank sliders.
2) Off
Basic Vocoder function
3) Silence Bridging
The Filterbank function will fade in when there is no speech. So there is always a coloured Excitation signal. While you speak, the colour is set by the speech. When you don't speak, the colour is set by the 20 Filterbank sliders. This allows a seamless blend of ariticulated and non-articulated sound.
You can set the threshold - how many dBs down the speech signal is, before the filterbank is engaged -, and the attack and release time of the filterbank fade in/out, with 3 potentiometers.
I have reduced the expensive, 1% capacitors to two values: 10nF and 47nF.
That way, you can buy them in larger quanities and they won't be that expensive.
You will need about 150 pieces of 47nF 1% and 150 pieces of 10nF 1%.
They are available at www.rs-components.de , order number 169-326 and 166-6421 (These are bags of 10 pieces.)
You'll need a lot of other capacitors as well, of course, butthese can be 5% tolerance - not so hard to source.
Speech Input Amplifier, Tone Control and Opto-Electronic Limiter (Tone Control Part inspired by ETI Vocoder)
Attack Detector (for Slew Time Symmetry) (Inspired by EMS 2000 Vocoder)
Voiced / Unvoiced Detector ("AC Hysteresis" function inspired by Sennheiser Vocoder)
Silence Bridging / Filterbank Control
Slew / Freeze (Inspired by EMS 2000 and 5000 Vocoder)
Synthesis Amp, Compander, Noise and S-Generator (Inspired by EMS 3000 Vocoder, ARP Quadra Phaser, and EMS VCS3)
Output Amplifier
Power Supply
Channel 1
Channel 2 (Inspired by EMS 5000 Vocoder, though I have no idea what component values they used.)
Channel 3
Channel 4
Channel 5
Channel 6
Channel 7
Channel 8
Channel 9
Channel 10
Channel 11
Channel 12
Channel 13
Channel 14
Channel 15
Channel 16
Channel 17
Channel 18
Channel 19
Channel 20
Living Vocoder Component Overlay
This is a preliminary BOM (based on the yet untested component overlay). Oscar Salas made this for me - thank you so much, Oscar!
I am stupid.
You probably knew this before, but now I know it, too.
PCB arrived today, without the component overlay silkscreeded. I always order with silkscreening, but for this project, of all projects, I forgot to check the right box.
This will immensely increase the "fun" populating the prototype. No Ichthys either.
But don't worry, the PCBs I'm going to sell will be with silkscreening, of course.
Anyway - here's a picture of the PCB with 141 IC sockets soldered in:
Nothing was exploding.
Current measured on +12V and -12V was about 500mA each. This is without signal, and without channel LEDs.
Expect the current to stay below 1A (DC) with all LEDs turned on.
AC current (fuses after transformer) read 900mA each. Expect this to stay below 2A with LEDs and all.
So the 80W toroidal transformer (2 x 15V secondary) is slightly oversized, and exactly the right choice for thi sproject.
I found this old sound clip on my PC today. It's from a previous vocoder project (14 channels). The Speech signal is frequency shifted with the FS-1, and then used for vocoding.
Short mp3 clip here.