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What the weirdness??
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Summer has started, therefore it’s again time to build some synths… I’m finally trying to get into just building on PCBs instead of stripboard. Currently practicing by doing an improved mic inline preamp (Multicomp makes just perfectly sized XLR attenuators that can be gutted!), soon I might take the leap for dual-PCB layouts 
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I’ve finally soft “launched” my site for modular stuff, with only a few pages for now, but i plan to have a lot more eventually. I worked all day on a little gimmick you’re gonna love and/or hate… click to see what I mean, and let me know whether your computer catches on fire.
(Main tech under the hood for anyone into this stuff: Astro.js, Svelte, Three.js, Threlte.js, MDX, Sass)
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the movable components? pretty cool actually…
will have a proper look tomorrow when the toddler is having his afternoon nap
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They break on mobile for now sadly haha, i will have to figure that out. There’s fewer on the subpages to avoid making the gimmick become too annoying.
Also, i completed the assembly (but not the programming) of this mixer i designed months ago! (I was a bit out of the game in the recent months).
The VUMeter uses a Charlieplexed topology and will be driven by an ATTiny402. It’s not been programmed yet, so I have no idea if it works… But I confirmed the 6 mixer channels, the send/return, the normal output, and the amplified line out work.
If curious, I have a build thread on my Fediverse account that you should follow under no circumstances:
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Hi @AriaSalvatrice,
heads-up about a problem with Aria’s Honking Synths on PC + Chrome, hope it helps…
If I follow a link then click BACK button, all the moveable components appear as separate white sub-windows
Fixed when I click REFRESH
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Turns out back and forward don’t clean up old webGL contexts fast enough that the previous page still counts towards the maximum of the current page, computers sure are fun! I’ll have to draw them all to a single offscreen context then crop bits to display on screen of it in an update
Nothing better than 1:1 scale model to figure something out
Now I got Charlieplexing working on the mixer
Still need to program a legit VU Meter. Definitely gonna use some ATTiny402 for pretty much everything from now on… 6 pins with ADC and PWM that work on 3.3V and 5V for €0.5? Gonna buy a whole reel lol. (Well - after looking it up, 412 look better for the same price, but yknow)
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Hi @AriaSalvatrice - different shed-based user here!
On my fancy 4K office monitor everything on your site is pulled to the right:
I may also have tried to drag around Miles “Tails” Prower 
It’s lovely to see an explosion of colour in a world of black and white modules - both for the site and your rack. Love them both.
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I’m experimenting with a FUTABA VFD type 16-SD-01Z. It is a low voltage fluorescent display which has a matrix of 16 characters each sizing 5 x 7 dots. It measures 9.5 x 2 cm, so this could be used as a vertical VU-meter, or maybe as a display for a yet to be designed sequencer or something similar in my euro rack. It needs 5V DC, 15V DC and 5V AC. I’m contemplating using a simple oscillator to generate the 5V AC. I do not know yet how much power the 5V AC will draw, however. Anyone have any experience doing this?
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I don’t expect this carboard synth to last more than few days worth of use, but i won’t need it to. Just need it to last long enough to try my idea on the computer.
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Anyone ever tried to connect an OUT to an IN on a 960 and noticing that this does not work as expected? The sequence then does not start on that IN but on IN 1.
I was playing around with my 960 sequencer and wanted to experiment with short sequences by sending an OUT to an IN. This is not possible in the standard version (I have a B960), but if you introduce a short delay in the pulse signal, it will work. So I designed this small circuit (Pulse-Delay-O-Matic for B960) which gives a rough delay of 0.1 mS, I chose this just for experimentation, so it may work with other delay times, and tried it. It worked nicely.
B.t.w. the circuit needs hardly any energy. So one way of coming up with a DC voltage I tried was to get it from the 3rd row of pots of the 960 or a clock source I had running. I used a diode and a cap for smoothing the output voltage. That worked nicely. I also tried a euclidean (pulse) sequencer as a power source. Depending on the number of pulses, within limits I could rhythmically have the sequencer switch the link on or off. Nice !
So … a signal in a modular can not only be an audio signals or a control voltage, there is a also the possibility that a signal can be a power source !
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After filling my first case with modules built on stripboard, I’ve now successfully designed and ordered my first pcbs for a kickdrum module based on the design from Moritz Klein. To my surprise the module worked right away 
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I love this kind of mod! Brilliant idea. Have fun.
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Well it took a long time to get the new cabinets made, and then I started building modules again… But here’s the beast in its present form -
There was space to fit my old FX2000 alongside the PSU in the base unit, and of course the new (top) cabinet is nearly full already. I’d intended to put the SQ-1 in there but decided to build a derivative of the Fonitronik VCPS8 sequencer instead. Here is a sample of it running as a 16-step sequencer with a varying step pattern (along with some Turing Machine driven drums). The Theremin style controller box uses a couple of Sharp GP2Y0A distance sensors (a present from my son) and a couple of joysticks that were in my parts box for years.
Here are more details on some of the new modules for anyone who may be interested -
PSU
3 switch mode power supplies; 5A for +12V & +5V and 2A for -12V, each with its own volt/ammeter. There’s LC filtering on each line in the cabinets to deal with high frequency noise from the PSUs. The base unit has four outlets each supplying +12V, +5V, -12V & GND to a cabinet (using aircraft connectors), plus four 5V USB outlets for the SQ-1 and anything else that may be USB powered in future.
Controller box
Each channel has an attenuverter and offset control and there’s a voltmeter display which can be switched to any channel to assist setting the range. The GP2Y0As have a slightly quantised output so there’s a glide control (high-off-low) on each of these channels. Not the best way to control pitch but can be effective for filter cutoff or volume control. Joysticks are 2-axis static and 3-axis self-centering. The latter has a push button with both V-trig and S-trig outputs.
ADCequencer
This 8-step sequencer is based on the VCPS8 by Fonitronik but with some significant differences. Firstly it has two analogue channels so can produce two different voltages at each step (hence two potentiometers per step). This opens up a lot of possibilities, e.g. two VCOs, VCO & VCF, VCO & VCA or (in conjunction with a synchronised analogue switch) as a 16-step sequencer. The sample above is of it running in this mode with a breadboarded analogue switch. The other innovation is the addition of a freeze circuit which allows the ADC to be stopped either by a switch or by an incoming gate signal. This gives a great use for the otherwise slightly pointless gate output of the VCPS8. Connecting this output to the freeze input prevents the pattern changing while a step is active and avoids glitchy effects due to a step turning off while sounding. There are quite a few other behind the scenes modifications as well - full details are already on GitHub.
YuSynth LFOv2
I built a second one of these to use as a clock for the Turing machines and the ADCequencer. I changed some of the component values to reduce the current draw (those ammeters make me a bit paranoid!). But I found a couple of other issues. The first (also on my original YuSynth LFO) is that it was impossible to get good triangle and sine output on both the FAST and SLOW settings. I’m not the only one to encounter this and I found a brilliant fix by gabbagabi on ElectroMusic.com. I added a variant of this to both my LFOv2s. The other issue is that the Pulse output is not clean at frequencies less than a couple of Hz due to some jitter in the comparator op-amp which converts the saw wave into pulses. I fixed this by adding some positive feedback to the comparator. Finally I adjusted the pulse width control to allow a much wider range of duty cycle than the original 10-90%. I’ll be posting a schematic with these modifications on GitHub.
Pulse divider & Boolean Logic
Based on the CGS36 module, this has extensive modifications to reduce the current draw - primarily using an on-board 9V supply to provide the output voltages rather than low impedance / high current voltage dividers. I removed the XNOR output from the XOR circuit, and normalled the AND, OR and XOR outputs to 3 op-amp inverters for the three NOT gates. There’s also a buffered copy of the input clock as a ‘/1’ output. Details will be on GitHub in due course.
Scriabin CV-DMX
Named after the famously synaesthetic composer, this is a two channel CV to DMX converter using an Arduino Pro Mini driving a MAX485E (as in some of the commercial Arduino DMX shields). It works well with RGB LED PAR cans. Each of the DMX channels can be switched between RGB and HSV (hue, saturation, value) colourspaces. In the former there’s a CV input and initial level control for each of the red, green and blue levels and in the latter the same inputs control the hue, saturation and value (brightness). The advantage of the HSV colourspace is that, by setting the saturation and value (brightness) initial levels to maximum, a single control voltage can be used to access the full range of available hues. I’ll be publishing details of this on GitHub.
And what about that tempting empty space? It was going to be a Triple Sloth clone, but having discovered the ability of the ADCequencer to work with 16 steps as well as its native 8, the next module will be a combined 4-stage frequency divider / analogue switch module. And that means I’ll need another cabinet for the Triple Sloth and a few other modules a bit further over the horizon. This way madness lies???
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PCBs arrived and got to build the inline preamps finally on PCBs.
Photo of the guts before packing it up.
With single JFET pair (stripboard version) the preamp seems to give about +27dB gain and with four pairs (PCB version) +33dB. I used 2SK209-GR JFETs as they seem to be the best choice currently.
Tried also to see how much these improve signal-to-noise-ratio, my current ADC is too potato to see the difference (that is the noise floor in the pictures, the peaks show the bad 50Hz mains supply rejection lol)
But anyways satisfying results from something that costs less than 10€. I will try to put the gerbers on PCBWay after some more experimenting.
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Hi all
some add to my Tchula pedal diy
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A quick update. The schematics of my modified YuSynth LFOv2, CGS36 PulseDivider and Boolean Logic and the Scriabin CV-DMX module are now all available in my GitHub repository. Hope they may be useful for someone!
If you want to use the KiCad schematics or PCB layouts you’ll probably need to download my KiCad custom symbols and footprint libraries too.
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