zynthia - sequencer synthesizer

I've started to work in KiCad and love to use the buzzard library for labels now. The 16 step sequencer is basically two zynthias (CD4028, CD4029, CD4051) that either count to 8 together or to 16 one after the other. The two stages had to be mixed with an LM358. I tried a TL072 before, but that didn't seem to work. Maybe the LM358 likes DC better as I did not supply negative 12V to the board. I'm using a CD4070 XOR logic gate to be able to invert the second stage with a switch. Still have to route 48 air wires, but I'm getting there. This is a revision, I had the first board for 8 months and was only yesterday able to fi the mixing part of the two stages.

https://github.com/davedarko/Zynthia16

I was watching a review of a modern sequencer and saw it going back and forwards. Thought to myself I could maybe connect the "overflow" pin of the 4029 and the forwards / backwards selection with a 4017 / 4022 chip. Need to investigate that :D

I've been asked for a DIP version and this is basically the latest SMD version with swapped parts and a bigger PCB. Ordered at JLCPCB in red.

ToDo:

check if C2  needs to be a 10th of current value

always wanted to do this, but it needed a tindie message to force me to finally draw this.

@WooDWorkeR  asked me to join the Drehkommando meetup at c-base and since I also had to bring him some goodies from the Chaos Communication Congress, I couldn't say no :D https://twitter.com/woodworker/status/1084192948718370816 we were able to add zynthia 2.0 to the pile of wires and noise gadgets and it didn't sound too bad. Especially when played loud ;)

But I noticed some issues that I wanted to work on later. I had no control over volume at all, something I was able to fix with a variable resistor used as a voltage divider on the output. I also had a lot of high pitched noise on the output, something that I wanted to tackle with a High Pass filter. Yes, you've read that right - I was stupid until I noticed I need a Low _PASS_ filter instead :D 

I then combined it with a simple dc-offset filter - there's also a High Pass filter in the schematics taken from stackexchange. 

https://electronics.stackexchange.com/questions/319857/anti-aliasing-filter-dc-offset

Followed by a fixed Low Pass filter and previously mentioned volume knob. You can see spot the two signals here, yellow is coming directly from the 40106, blue is after the filter, but before the volume potentiometer.
https://www.instagram.com/p/BslYsZqnE6b/

Some slight changes to the capacitor values allow the sequencer to run a bit slower. The synced pitch mode now has a wider range of frequencies. The tone range of the knobs is now deeper.

With the pink board I also fixed the direction of the potentiometers, when you now turn them clockwise, the tones go up.

working on that youtube channel makes me finish more projects, as it seems :)

Wow, it has been a while! I have the SMD boards assembled for a while now, but never came around testing them - I was just not interested in soldering all those resistors and LEDs again to get something that does almost exactly the same like the original does. Until yesterday, when I wired up a 90ies color schemed board :) check it out over here, I'll have a youtube video incoming soon, too.

https://www.instagram.com/p/BloIPnCAMTR/?taken-by=davedarkocom

There will be updates, but here's a sneak peek for @al1  s version:

https://hackaday.io/project/9038-me-buildingusing-other-peoples-ideasprojects/log/67240-6-zynthia

I still have to update the OSHpark Board, there are some minor label changes (if it works at all, that is :D ):

C2 is a 10nF cap

C1 is a10uF cap

So this board should have all the bells and whistles it can:

• 8 LEDs
• 8 Tone knobs for pitch
• up/ down switch for the counter
• binary / decimal switch for the counter (count to 8 / 10)
• Synced oscillator switchable
• Speed for the counter potentiometer
• Sync / Pitch knob

Thanks to @al1 I'm now aware that I've mixed up the GND and VCC symbols from the schematics of @Elliot Williams :D So now it's corrected and everything looks even cleaner! Definitely will sleep on ordering this one (hopefully al1 will have another look, just to be sure) :D I'm not looking forward to the boards arrival - straight to the totem of failure, I guess.