My build progress

I built a second one


for my daughter (7 years old)… it had to be these exact key-caps :slight_smile:

spread the :heart:

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Lattice (kosmo format mutable grids) is finally working! Will have ~3 to sell probably :slight_smile:

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I changed the simple mixer (bottom right but one module) to a bespoke version that allows me to mix the raw modulator and/or raw carrier signal with the vocoder output.

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New breadboard, new oscilloscope. Nearly back to where we were a few weeks ago with the @moritzklein x es.EDU VCO…


Have now put all random chips that were on my desk into a Holy Smoke! container, along with a new one. :person_facepalming:

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I added some modifications to my latest project:

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Slow more progress this weekend, mainly due to being a Dad taxi… Kept following along with the @moritzklein x es.EDU VCO manual, but got stuck on the tuning step. Just couldn’t get the thing into tune at all, the Noodle Toaster wasn’t much help, other than showing me how far off I was. It felt like the trim pot wouldn’t go far enough.

Anyhoo, decided to spend some time in DIYLC recreating the hand drawn breadboards for my set up, with all the Kosmo Mini helper boards and what not. Once that was done, I popped out to the office and stripped the breadboard, while doing this I check the values of a couple of resistors to make sure they were going back into the correct bag, and found what I’d thought was a 1K5, was actually a 470Ω, which would probably explain why I couldn’t tune the thing.

So I built the breadboard back up, following the DIYLC layout I’d made. It sounds a lot better now, although it’s still really high pitched when the coarse POT is in the middle.


I was using the Noodle Toaster’s Control Voltage generator function with the “1 octave arpeggio (alternates between 1V and 2V), 2 octave arpeggio (alternates between 1V and 3V), chromatic scale (goes from 1V to 2V by 1/12V increments)”, the problem is, I don’t know what note 1V, or 2V is supposed to represent. The Noodle Toaster’s Audio input function gives me a note on it’s screen, I just don’t know what that should be when my coarse POT is pretty much in the middle of its range, and how the 1V (etc) is supposed to change that…?

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1 V per octave is standard — change the CV by 1 V, the pitch should change by 1 octave. What isn’t standard is what pitch corresponds to 0 V. Anyway, usually you don’t really know what voltage is going into a VCO: There’s whatever you put on the CV input(s), but these are summed with whatever voltages are coming off the octave switch or coarse tune knob, the fine tune knob, any internal center pitch trimmer, etc. Still, if you put the knobs near center and put 0 V into the CV inputs, some VCOs will produce about middle C, some will produce something around C0 or C1 (below or at the lowest C on the piano), some will do something else. In designs with a center pitch trimmer you can set that for whichever behavior you prefer, but some VCOs don’t have that. And then just for more fun, different MIDI to CV circuits output different voltages for the same MIDI note input; some will let you redefine that with a configuration change, some won’t. So with the same MIDI going into different MIDI to CV and from there to different VCOs you can get outputs that are four or more octaves different. Fun, isn’t it.

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I just naively assumed that the whole volt per octave thing was balanced around a set octave and actually meant something. Like 3V was middle C and thus you had two octaves on either side. I shall stop worrying about it and carry on… :roll_eyes:

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Here I am trying to design my own clock module, and it appears you have beat me to it.

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Been feeling pretty terrible the last couple of days, so decided to put those crimps that arrived yesterday to good use. This will eventually be my take on the Super Simple MIDI Keyboard, but for now the buttons just illuminate the onboard LED on pin twenty five.


I have also implemented note on and note off MIDI commands, but have no way to test that they’re being sent on UART TX0 (pin GP0). Hopefully the mail person will bring me a MIDI cable and chassis mount in the next few days.

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Hey gang.

My old cobbled-together case was rubbish, so I’ve started cobbling together a new one. Two rows of 40HP Eurorack is in progress. (Actually 41HP, because I haven’t really got much of a clue what I’m doing. I wish I’d gone for 40 properly so that there could be a comfortable margin at the ends.

The box is an IKEA crate. I love them for projects, and I had the usual bit of IKEA serendipity when I discovered that there was just over 257mm between the corner supports if I cut one half of them back a bit. 257mm = 2*128.5 = two rows of Eurorack modules. Nice! (I’m resisting saying 3U/6U because I’m a pedant and, having read the Doepfer specs repeatedly to get the sizes right, I know it’s a bit hand-wavy…)

Rails are 3D printed, 4mm deep 2.85mm holes mean M3*6 screws will cut their own thread. I’m working on the central one at the moment, as is probably obvious! I designed the rails to go around a 6mm threaded steel rod for strength (selected because I’ve got 8 metres of them on hand) which I’ve cut slightly long so that it can get pushed into the soft wood case to help brace it. The top and bottom rails are then screwed into the top and bottom pieces of wood as well.

The central one is going to be in several parts to aid with the printing - the alternative was to have masses of support - and I think the rod will be slightly longer again, with holes drilled in the case for it to go into and printed endcaps to cover.

Although Eurorack sized, I’m using my own power connection standard because I don’t actually have any ‘proper’ gear that demands the 10-pin connector.

Anyway, there you go :slight_smile:

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Following up from yesterday, I now have a 3D printed/wooden/threaded steel rod Eurorack case. Last thing to make is a lip to go across the middle, and glue it in.

Mixer and two (unlabelled) PT2399 reverb modules mounted temporarily, I haven’t made any other Eurorack-sized panels yet. Power etc will get sorted out first, though.

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Finished a Polykit Spring Reverb to drive an Accutronics 8BB2C1B

Another one in the making to drive a 9BB2C1B (42cm spring)

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I think I have that keycap set.

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Did you change any values for Input Coil Impedance?

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Completely refactored all the MicroPython code I wrote earlier in the week, so most things are now done in PIO. Wasn’t sure how to test the MIDI messages, until I realised I could just plug UART 0 TX into UART 1 RX and unpack to see if they were what was expected; they were.

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ok so its moving along only 8 more of the 15 boards to go …

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I used the recommended values for 150ohm input impedenance.

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Power supply and rails are installed!



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