Julien10/03/2019 at 14:43 0 comments

    It's been a long time so here is the result of the video synth, it works quite nicely. On the left there's a version without the VCO and I must say it isn't as fun as the one with it. I'haven't tested the envelope filter.
    The Luma switch does its job but is very unpredictable depending on the mode the synth is in.

    However as it, it draws a fair amount of current and I wonder if I can replace the analog VCO (2 LM13700 and few opamp) with a 32bit processor as it was intended at first. I made few tests and it could be possible as the VCO doesn't need to go higher than about 4khz.

    Now I guess it will either sleep in dust or end up at a shop for tattooed hipsters.

  • Current state

    Julien04/13/2019 at 11:18 1 comment

    The project is still going on. Almost done. A syncable VCO modulated by another VCO have been added and can also module the 4bit converter and the keyer. Quite happy with the results ! Next steps, building a box for it  and maybe built a version with a Microprocessor for the additional modulation (and reduce part count). 

  • ADD-ON

    Julien03/11/2019 at 15:50 0 comments

    Knowing that everything work, I kinda become lazy on this project (also that I switched to a linux machine, what a change...) however the project took a step further. I originally planed to only use the video processor but it'd be a miss to not add at least an horizontal oscillator (strips). Considering the low maximum frequency (about 5Khz) I went for a LM13700 VCO (cf. datasheet) and some waveshaping to have proper amplitude and bias. Vertical oscillator (bars) is a bit more tedious as the frequency should at least go to 500khz (but mroe about 1Mhz)

    (The decision for the additional circuits was hard, considering the modularity of the system everything could be done. From a simple video modificator to a  fully modular with patch cable. But I want to keep the thing simple and easy)

    I also made my mind, no microcontroller on this project. Full analog for all the nerds out. A simulation of what it could look like . The boxing is always a pain for a one-off project.

  • no idea for a title...

    Julien02/24/2019 at 14:25 0 comments

    the board is working fine. I made a crude test jig out of MDF panel. I decided to give a separated control for the solarize fonction. I was fearing for the LT1054 to be noisy but things are very clean. I'm now working on a daughter board to produce a Horizontal VCO (LM13700) and other things to play with (burst, enveloppe). However even as it, the circuit is fun to play.

  • First Breath

    Julien02/04/2019 at 13:17 0 comments

    The input/output of the circuit is working fine. The NX5DV330 is doing fine as well(but no longer manufactured).

    two things to consider for the next round. 1/ use very sharp clippers to cut lead otherwise it may damage pcb traces (doh...) 2/ don't confuse TSOP20 package with SOIC20 package (doh...x2).

    I'm still undecided on what signal to add with the video one. Currently I'm thinking about a noise source through a filter  and some random crap from a microcontroller with a bit of entropy (microphone) sent to the mixer to create luminance bursts.

  • Video mangler

    Julien01/21/2019 at 13:54 0 comments

    I had this project in mind for sometime now. It is inspired by an old 80's magazine project called the "video palette". It offers several effects to toy with the video signal that has been split from the sync signal. There're two big circuits, a keyer and a posterizer and a rotary switch just send the proper signal into the keyer (negative, posterizer,...). There's also a lowpass filter to blur the image.

    I wanted a bit more lo-finess to it so I added a microcontroller (STM32F03F4)  and a 12bit DAC to generate others signal that could be mixed with the video signal (as well as a midi input). Considering the lack of video encoder, the signals will only be black and white.

    Considering the bandwith  requirement it's always a bit tricky to select part, especially for the multiplexer. Too much ON Resistance in the switch and you loose sharpness. For the main multiplexer (the one that split the signal and re-sync it with the modified video) I designed the PCB for two options: The NX5DV330D which is a video-multipler and could the job nicely and the trusty CD4053.

    NX5DV330 datasheet