The last couple of days I have been fighting with a DIY variant of the Buchla Dual Oscillator Model 258. I couldn’t get one of the two PCBs to output the right waveforms.
Tonight I wired the second PCB and was finally able to fix the first PCB. I will not bore you with the details but it suffices to say that I overlooked the obvious (again)… 😉
The picture on the left shows the two PCBs, containing a sawtooth oscillator and a square wave oscillator, mounted to a wooden prototype panel.
The waveforms aren’t exactly perfect but the original Buchla oscillator also didn’t output a perfect square or saw waveform. However, I will try to optimise it a bit more.
The beauty of this oscillator is that it has a wave shape function on board. You can change the output waveform from sine to square or saw by just turning a knob on the front panel. As with every function on this VCO this is also voltage controllable. Very nice!
I did a quick sound test and it sounds… different. And that was the whole point of building this VCO.
Comments
10 responses to “Buchla 258 Dual Oscillator working”
Hi Andre,
That’s a very nice looking prototype and the waveshapes look really good.
I agree with your decision to use a standard pot for the fine tune control instead of one of those smaller, cheap pot/trim pots (Model P110K made by BI) with the plastic shafts that a lot of DIY’ers seem to be using since they are really small and don’t require a knob. However, since this Fine Tune pot will likely be used more than any other pot in the entire module, I think a standard pot makes more sense since it should be more reliable and should last longer (depending upon what pots you use).
I was concerned that a standard pot in this location might be a tight fit (especially on the front side once a knob was added), but apparently, this was not a problem for you. So I consider this to be good news.
I also really like the pot bracket that you made. Did you make it yourself? If so, good job and nice design.
I can see that you used 4 hex standoffs to hold the 2nd PCB. (I’m talking about the 4 hex standoffs that separate the 2 PCBs from each other. (They appear to be about 1 inch or 2.5mm long).
Do you remember what the dimensions (diameter & length) were for these 4 hex standoffs?
Do you use these same size standoffs for the majority of your other Buchla modules?
Have you ever needed standoffs that are longer than these for any of the Buchla modules that you have built so far? [Obviously, I can see where you might use shorter standoffs. (See the next 2 questions)].
What are you using to separate the bottom PCB from the pot bracket? They appear to be some sort of spacer, but the picture really doesn’t provide a good view of them.)
If you are using some really short standoffs or spacers, what is the height (1/4″ or 3/8″)?
I plan to build this module within the next month or 2 so that’s why I’m asking all of these questions.
Hi David,
Depending on what you’re planning on installing on the panel it can be a tight fit. The panel design I did for the “Mutant Complex Waveform Generator” is pretty stuffed. There is no more room for anything else. You can see a picture of a test panel in the SDIY Buchlaesque section:
http://www.ecalpemos.nl/sdiy/buchlaesque-modular/mutant-complex-waveform-generator/
I made the pot bracket myself. It’s not that hard using sheet Aluminum from the hardware store.
The hex standoffs are M3 and are 20mm (0.79″) high. I bought them on eBay some time ago. The height is OK, I guess you could even use 15mm ones to make it more compact.
For the lower PCB I use simple plastic spacers, 5mm (0.2″) tall.
Hope that helps. Should you have any more questions don’t hesitate to ask.
Hi Andre,
Thanks so much for your help. I also make my own pot brackets as well as most of my front panels. I know a machine shop that will sell me 1/32″ Aluminum and cut it to size. All I have to do is bend it accordingly. (I can usually get them to make me 20 brackets for about $20 (USD).
I have only made MOTM-format panels so the Buchla format is something new to me. However, the standoff lengths/heights were about the same as those I use. I think my short standoffs are 0.25″ in length amd the long ones are 0.75″ to 0.8″. So I’m glad to know that my 0.75″ to 0.8″ will be long enough. Otherwise, I would have had to stock another size.
Would you have any 258 PCBs you could sell? Or trade for SFX>>>
I am a Sound Designer/Editor here in Barcelona and have nice 500Gb sound library I have collected over the years. If not, do you have the contact to the PCB fabricator you are using?
Again, Super awesome work! Very Inspiring!! P.s. Always cool to meet new people in the film world..
Hi Benjamin,
Sorry, I don’t sell the 258 PCB. Those were designed by J3RK over at the Muffwiggler forum.
Kits and/or panels will be available soon through Tonk in the UK: http://www.thonk.co.uk/
You can check out the following threads for more info and ask there: http://www.muffwiggler.com/forum/viewtopic.php?t=26856 (PCB thread) or http://www.muffwiggler.com/forum/viewtopic.php?t=31038 (build/mod thread).
Sorry! Ok the 258J pcb are someone else… If you are interested , here is a link to
complete 258 kits going on sale soon!
http://www.muffwiggler.com/forum/viewtopic.php?p=1102982#1102982
OK. I just updated my reply above with that info but you already found out yourself 😉
hi there,
i also got the J3rk PCBs and i wonder , how do you fit his design to the original buchla style panel?
something between J3rk panel and the original panel doesn’t match (the original has 2
control inputs and only one kind of FM (linear?) so how did you match it to the original panel?
thanks !
I posted a wiring diagram on the Muffwigler forum a while ago which explains how to wire the J3RK PCB for a Buchla panel.
Check out http://www.muffwiggler.com/forum/viewtopic.php?t=31038&postdays=0&postorder=asc&start=266
You have to be logged on to see the diagram.
Hi andre
Thanks a lot for that!
So i guess that the FM in the original panel probably refers to the expo FM?