Hello all! I am a very green but highly enthusiastic musician who wants to pretend to know what I’m doing. I would like to make a drone synth using the SSO oscillators. The concept is relatively simple. 12 osc total, 4 groups of 3 osc. Each group will go to it’s own mixer then to a filter. These groups will be setup to go from low to high in frequency like a string section (bass, cello, viola, violin). These groups will then go to two delays which can be fed into each other, each with their own ouput (to be used in stereo). I have simulated this idea on VCV rack and am happy with the organic feel of how everything works together. Forgive the optimistic goals coupled with electrical ineptitude. I will learn, no matter how long it takes.
Questions
1-How could one control not only individual osc freq, but also have a main pitch knob for each group of 3 osc?
2-Would one be able to add one vactrol CV-in for each group of 3 oscillators pitch?
3-Will these tiny reverse avalanche oscillators provide enough output to be used with an MS20 style filter?
4-How can I add another output to the SUPER SIMPLE MIXER which I have found on this site?
5-I’m sure this is a long shot but could I mark on the front panel pitch pots the general area in which certain notes would be, or would there be too many variables to be accurate in any way. I would just want a few notes (D,A,C,G)etc.
6-Should I put this idea to rest until I have more experience with electronics?
Thanks in advance… I have been lurking and reading for hours here every night. I’m in love with the creativity and smarts of this forum.
I think go for it! The first step of the project is probably to build 3 SSOs, which is a reasonable novice project, I think?
I read your tuning questions to mean that you want to be able to do something like the following - set a group of three oscillators to say a triad, say C, E, G, then have another pot that would let you retune all three at once in a way that keeps the relative distance of each from the other - so you could tune it up using one knob to F, A, C.
I’m am personally sceptical that would work without being really fiddly - I’m not sure the SSO circuits could be controlled with relative precision in that way, as I imagine the choice of transistor would interact with the resistance change in a way that would mean different SSOs respond differently to the same amount of variation. Though I don’t know for sure, I haven’t tried it.
That being said I do have a potential idea on what you could try.
You could create a potentiometer (which will be your master tuning pot for your bank of three) that varies voltage from day 0v to 5v (make this range the same as your CV input I think).
Then create a non-inverting summing mixer with an op-amp to mix your pot voltage with your CV voltage.
That is four LED drivers. Send your mixed CV voltage into one of the four driver inputs, and then connect the output to the three LED sides of the vactrol for your bank of three oscillators, and wire them in parallel.
You’d get a master pot and cv in for your bank of three that would control pitch, but whether it would control it with enough precision I don’t know.
If that’s the goal, it’s harder than you might be thinking.
With the SSO with simple voltage control as shown on the LMNC website, the control is (approximately) linear, or V/Hz: Change the voltage by some amount and the frequency increases by some number of hertz.
But C to F is not the same number of hertz as E to A, it’s the same frequency ratio. So you need a setup where changing the voltage by some amount multiplies the frequency by some value — a volt per octave setup. V/oct is much more challenging than V/Hz.
Also, let me ask why you have chosen to make this project SSO based. Yes, it’s a very low parts count oscillator, but a quick search will show it’s not necessarily easy to get it working and doing what you want. It relies on a transistor operating in a mode transistors aren’t meant to operate in, and that complicates things.
A 40106 oscillator uses nearly as few parts in a less quirky way. You can build six oscillators with one chip, six resistors or pots, and six capacitors (though they’ll crosstalk, so it’s better to limit yourself to three oscillators per chip) with less fuss than six SSOs. You can get both square and ramp waves.
555 oscillators are pretty simple too, as evidenced by the popularity of the Atari Punk Console as a first project.
Go ahead and use the SSO if your heart’s set on it, but consider the alternatives if you haven’t.
You want two (or more) outputs from the same mixer, all having the same signal?
As shown at STUFF - LOOK MUM NO COMPUTER, the output jack is connected directly to an op amp output pin. You can just wire another jack (or two or three) to the same op amp pin to get multiple outputs.
However, if I were doing it I’d add a 1k resistor in series with each jack (including the one already shown). That will limit bad consequences if a jack is accidentally connected to ground or a voltage rail.
Thank you so much for all your replies, all very good ideas. I am stuck with strip board layouts while I practice., and I am having trouble finding a stripboard oscillator as simple and cost effective as the SSO. I don’t mind trouble shooting the SSO, and there are a lot of resources and information on them out there. I was aware of the struggles before I decided to go that route. If you know of any simple and small stripboard oscillators let me know!
I am not looking for accurate tracking or transposing triads accurately. I just waned a macro pitch adjuster for each group, so if they are all unison they could go up together in reasonable unison.
