Joined: Mar 11, 2014 Posts: 746 Location: New Zealand
Audio files: 41
Posted: Sun Jun 19, 2016 10:20 pm Post subject:
JH's Wasp VCF
Experimented with a PCB-material front panel. Seems to work so far. Only part that really bothers me is that I forgot M3 mounting holes, and had to resort to zipties (ugh).
I've built 2 Echo Rockets from MFOS (Music from Outer Space). I decided to remove the Echo portion of the circuit on one of them. This small unit has a really nice filter with CV control and external input.
Thanks for the comments. Just for comparison, here is the original MFOS Echo Rocket I built. The Echo distorts on this pretty easily which is why I removed the Echo from my 2nd unit.
Finally completed building and de-bugging my MFOS 16 Step Quantized Vari-Clock Sequencer! Definitely the most complex module I've built - three boards: digital, vari-clock (stacked above each other) and analog, plus a small distribution strip.
I added a second channel (which just required a few more diodes), and also replaced the D-to-A clock rate resistor with a 50k trimmer. Getting the timing to work properly so that no and one steps behaved was a nightmare even with an oscilloscope.
A lot of board to panel wiring....
Well worth the effort though!
Peter
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That looks fantastic. MFOS builds have lots of offboard wiring but they're fun to build and fun to play with. I'm currently building some MFOS modules that I think I'll put in a FracRak.
I've started to build a simple modular synth (my first one!) Everything is built on veroboard so far, mostly layouts from others here...for the VCF I made the layout as I couldn't find one anywhere else. The front panels are currently made from corrugated cardboard, and when I decide that I like a module I will make some proper panels up.
I have also started to make the PCBs for a MiniMoog clone and designed an 'in the style of Model D' mod wheel which i've 3d printed, I'll put some pictures up if anyone wants to see them. For the PCBs I tried toner transfer first but wasn't getting on very well so bought some cheap photoresist film and am really happy with the results but it is a bit tricky to apply it.
Had one of these when I was a kid. Got it for a dollar at an auction. Redid the pads, cleaned it up. My 5 year old daughter loves it as much as I loved mine.
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Would he run out of solder ... no he manages .. ah no .. new roll needed :-) _________________ Jan
also .. could someone please turn down the thermostat a bit.
Joined: Dec 17, 2009 Posts: 497 Location: Rosmalen, Netherlands
Posted: Tue Aug 23, 2016 1:45 pm Post subject:
Cfish wrote:
Had one of these when I was a kid. Got it for a dollar at an auction. Redid the pads, cleaned it up. My 5 year old daughter loves it as much as I loved mine.
a "Magnus"? I have two smaller ones, one with chord buttons found at a thrift store, and a much smaller one I got from someone in the family without chord buttons (a 110v one, which needs a transformer overhere).
I have rested my soldering iron for a few months this summer, but now started to fill the next "cabinet" with modules.
So far there's one of Ray Wilsons (R.I.P.) Bipolar Wallwart PSU's, the Korg Ps3100 Triple-Resonator Clone based upon the schematics by Fonik (did a mix of some of some components from the schematics), 3x resonant LPG's and a Serge style Smooth and stepped Generator.
Started monday to build a clone of the Buchla 258 VCO based on the schematics floating here somewhere around (those with some notes by Jerk)
Well tracking over 5 Octaves was no problem... used only 3906 unmatched and with an KTY sensor instead of Tempco and as i want to save my remaining CA3080 for an TZ VCO somewhere in the future with an half of a LM13700. For the other trannies i used another 3906 and the other pair was two 3904... both FET's i used SK30.
Here i guess starts my problem... the waveform switching i solved with reducing the 680K resisitors down to 430K. Well the Saw is not as much wavy and fold as in the original but you can see those 2 humpbacks. The one thing i can't get work is getting a nice sine wave otu of the shaper with the other FET.
I always have at one edge a small steep flank on the signal... as can be seen on the scopeshot...
Anyone used 2SK30 for this and solved it or any other recommendations for easily obtainable and cheap FET's?
Edit:
If i can't find a solution to get a better sine, maybe i should just use the sine shaper Thomas henry used in his 555VCO... good to have a spare half of a 13700 there... or simply just leave it as it is... well it's not ideal but unique... will test/see/hear how it works and sounds with filters or wave shapers...
At least i should increase the level of the output to 5Vpp to match with my other VCO's...
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Joined: Mar 20, 2012 Posts: 2177 Location: Chicago
Audio files: 16
Posted: Tue Sep 13, 2016 3:18 pm Post subject:
The Buchla Sine is not very perfect anyway. The various trimmers all interact as well, so it's a case of tweak one, then the other till you find a waveform you can live with.
As far as i noticed only the trimmer for the sine affects the sine really in my built. When the waveshape control is turned fully in the direction when it's a "sine" it stays a sine, no matter if i input a CV for Waveshaping or not vice versa goes with the saw... when i turn the pot slowly into the middle direction the effect of the Waveshape CV get's bigger and in the middle it is at it's highest effect turning form one to the other shape and then turing the pot further the effect goes smaller until it's only a sine or saw depending in which direction you've turned the knob.
Is this common within this VCO...? Well i think it's fine it safes me a pot for Waveshape CV amount if it works this way.
As for the trimming of the sine i know remember i have used a similar way to get a sine out of the EFM VC LFO... just a few different resistor values and probably another FET... It was just bit low 1Vpp and i had to push a bit up to a hgher level carefully without not making a triangle again...
But i really like the FM sounds this VCO is capable to produce... Really weird things can happen, but also as an normal VCO for leads sounds or so it's great... _________________ https://soundcloud.com/bastian-j
Good Idea... haven't looked there yet... but i always thought that would be a more tech-talk orientated and less on DIY focused site...
But i registered there sometime ago and still have zero posts at Muffwiggler...
Tried it again with matching my diodes and also the 1% resistors i already had as close as possible... didn't changed anything...
then tried to trim again and looked at the scope when these edge got smaller... after a time it didn't changed anymore... so i was at the end of my trimpot... now measured what i had between the wiper and the outer lug not used in the design... 0R so i possibly needed more than 20k... changed to a 50k trimmer and voila the edge went down an down and closer to a perfect sine... well 50 wasn't enough to close the gap but 100k i guess will do, try this later maybe... now also the saw is more closer to the original... fine
Edit:
I realized that i build a mechanical vibrato in my 258 VCO clone.... When i wiggle my cabinet i have a slight vibrato on my tone... looks like a cold solder point... _________________ https://soundcloud.com/bastian-j
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