My build progress

[fatboab]

Continuing from yesterday working Voice A of the WSG, I decided to start on the output section, it didn’t go well. I’m not sure what’s going on, but there’s just a howl of something’s not grounded properly noise, which blots out most of the weird noises. So I took out the POTs and striped it back to the bare essentials to see if that was working, which it’s not. If I waft my hand closer to the breadboard the noise gets worse and touching the 10M resistor that goes from the output back to the inverting input of the first LM741 cause the howl to turn into a screech.

So I shoved in the output buffer from David Haillant’s schematic, and now I get nothing, not even a whimper. So I guess tomorrow I’ll be pulling it all out and putting it back again, one component at a time and checking with the multimeter to see what’s going on.

Edit: Just remembered that there’s no point adding that second LM741 output buffer, as he’s running that one from +/-12v, which I don’t have. So that can all come out…

[Krakenpine]

I got one of those 20 eurodollar oscilloscopes from Ebay and built a improvised rig to attach it to eurorack case. Seems to work just fine for what I need currently.

[fatboab]

So I spent a couple of hours today attempting to get the WSG oddness filter section working. Unlike yesterday, we had some success. At lunchtime I stripped out all of yesterday’s mistakes and rebuilt it, but the effect was the same, just loads of something-not-grounded noise. I ended up checking the POTs with the multimeter to check that they were actually working, as they didn’t appear to do anything.

So I had another go this evening, stripping everything out and putting it back again. Firstly, I left out the POTs and reduced R11 from 750k by putting another in parallel, based on only using one voice. I was convinced that the signal hitting the op amp was so low, it was just amplifying noise, rather than a clean signal. With this in mind, I also replaced the 10M R4 with another 750k and this appeared to pass through all the weird noises from Voice A without any background hum.

So I wired the POTs back in, leaving the modified resistors, but the weird noises were gone. I tried changing a few values of R4, to no avail. In a last gasp try, I put the 10M resistor back in, and was greeted by oddly filtered weird noises.

It took a while to figure out what was going on, but at some point during all the fiddling, I must have flicked some of the switches and twiddled some of the knobs on Voice A. This appears to be enough to override the noise and allow whatever is being sent to be filtered, especially if the R3 coarse oddness filter is whacked all the way round.

MFOS WSG Oddness Filter oddness

This all making me think that there is an issue hidden somewhere within Voice A, rather than the filter. Although I don’t like the way the noise changes in loudness as I waft my hand over it. Probably time to take everything out and put it all back again while triple checking I’m doing it correctly…

Edit: realised this morning that there’s probably nothing wrong with Voice A, and it’s probably an issue with the oddness filter. Without the filter installed, when you unplug the power, it continues to makes fainter and fainter noises for about thirty seconds. With the filter installed, it goes dead the moment you pull the power. Shirley this means I’ve got some sort of drain somewhere that I’m not aware of, but where…!?!

[ehisforadam]

I went and did it, case number 3. Already got a few modules in it. Made a few digital modules by Hagiwo (quantizer, wave folding VCO, and Euclidean sequencer). I needed to add an input buffer on the sequencer clock… spent along time trouble shooting that one.

[Dud]

Nice !
what is this distortion ?

[ehisforadam]

It’s the “Euro Distortion+” in the Veryified Strip Board Layouts thread. I am not super happy with how it sounds. I think I need to play around with it a bit more. I also had a bad first impression of it because when I first built it I managed to misplace a resistor and made a couple other mistakes. I feel kind of silly about it because it’s so simple.

[BlackDeath]

Springy Sproingy!

[fatboab]

Still not sure what’s going on, but when you twiddle some of the POTs, the humming gets louder, so I thought I should investigate. First I checked the soldering:

Then I re-flowed every single pin on every single board. I then checked each one to make sure they were all in the right ball park and no shorts or anything:

When wiring all the POTs back up, I noticed that there was a missing connection betweenthe emitter of the transistor and the schmit trigger. Fixing that certainly changed things slightly, but not necessarily for the better, although the resonance POT seems to do more. Some POTs get about a third of the way round, then cut out, then start up again after another third of a turn.

I think the next step is to take it all apart and put it back with a bit more space between everything so I can clearly see what’s going on.

[CTorp]

Used the micro footprint to save space and I really like it! Quicker install and looks just as neat IMO

[popflier]

I’m having flashbacks to the Erica Synths modules!!! Phew…what a nightmare those were. I still do not have my bassline or VCO working, but to be fair I haven’t looked at it since I tossed it in a box of “to look at sometime in the distant future.”

[CTorp]

My bassline is still more or less unusable too lol. They released those modules and each had like 3 issues on Erica’s part so I grumpily put them aside

[Bpbby]

Finally getting there on my last panel. I have got the Digisound-80, the OBA, the Grrr Funky and Mult to sing all together.
I have made a video with the worst sound quality possible but I already love them. I am feeding the AS3340 VCO to both filters, no VCA, no envelope but they do sound both sound amazing.

Digisound-80 and Grrrr Funky filter 1st test

Some pictures for the spaghetti lovers.

I have the LFO and the delay to assemble and then I am done.

BTW I ended up adding a 5k resistor on the +12v of the resonance potentiometer to bring it to a ~12k total for the digisound filter and it is now self oscillating.
Digisound 80 filter

[Farabide]

@Bpbby

and then I am done

We all said that once

[Jos]

Ever wondered how @Hagiwo’s modules look if you line up a lot of them? Here is a look behind the front panels:

The pic was taken from this video:

[ $23 ] DIY eurorack modular synth YAMAHA PCM PIANO VCO with NSX-39 | Acoustic ambient sound source

[Jos]

I’ve been busy …

And the results arrived today:

Top: Power-Strip-O-Matic v0.1, you always run out of these things, so why not design your own?
Left to Right: Euclid-O-Matic v0.1 (3 boards), a euclidean sequencer with a twist
and Multi-Filt-O-Matic v0.2 (2 boards), a Bastle Cinnamon inspired state variable filter.

[heckseven]

I recently swapped out my FCUK power supplies for Mean Well Rt65b supplies in a couple cases and it made a huge difference for me.

[Farabide]

Did those snazzy orange terminal covers come with or are they home made?

[heckseven]

They are 3D printed, but I purchased them because I don’t have a 3D printer. You can find them here.

[analogoutput]

I’ve looked at that supply but have had a couple of concerns: First, while the +12 V rail is rated for 2.8 A, the -12 V rail is rated for only 0.5 A; second, the ripple spec on the +12 V is 120 mV which seems high. Any comments on these?

[heckseven]

I haven’t run into issues with the -12 rail yet but two of them powering a single 40x80cm box seems to be enough power for what few kosmo modules I can squeeze in there. I don’t think many of my modules use the -12V, but I would need to do a bit more testing to confirm.

I don’t know much about the ripple or what to look for, but this is a significant upgrade from a pair of FCUK power supplies in terms of module stability. Usually the first thing I notice is the instability on an oscillator when there isn’t enough power (my biggest frustration). The limitation for me on the FCUK supplies was the 12V 3 amp AC/AC wall wart (one for each supply). I did get a few fish tank AC/AC units that are 5 amp, but I will test those another time.

There are also a handful of different setups with these Mean Well supplies. Some folks connect COM to ground to reduce noise. I have not done that yet, but it is trivial to do if I notice noise (so far so good). Another thing I have seen is to add some resistors between 5V and ground to reduce noise.