Hey are there any simple circuits or stripboards oscillators that are able to output a sine wave? I know there are some vcos that are able to output it, but I’m just wondering if there are any oscillators that just output a sine wave.
If you look for a filter that can self oscillate it will output a sine when oscillating. Then by choosing the filter frequency you can tune it.
Generating good sine waves is non-trivial, especially if you want to make things voltage controlled (and also somewhat pointless if you’re doing subtractive synthesis). If a fixed bank is ok, you can take a look at this one:
Can something like this be used as a oscillator for a synth? Might be a dumb idea since this circuit might not be intended for synths, anyone know if it can?
The usual approach I’ve seen in synths is to take a voltage controlled triangle wave oscillator and shape it somehow by putting it through some transistor or diode network. These are not real sine waves, but decent approximations. There’s an example here on the forum.
Even a filtered triangle can look somewhat like a sine.
You can probably do something with a Wien bridge, but I think getting decent V/Oct voltage control is not quite as simple.
Yeah, that produces a sine wave, but it’s fixed frequency and (I assume) has a manual or no gain control. The fixed bank I linked to uses roughly the same circuit, but with a bit more components to manage gain.
To make an adjustable wien oscillator, you need to change two resistors at once, and you also need to manage gain – it needs to be 1× for the best wave form, but higher at first because otherwise it won’t start oscillating. Figuring out how to do that, and without introducing too much distortion, was a big topic some 90 years ago, and made some people rich:
For your personal interest, the method of using filters to generate sine waves is also discussed is SOS Synth Secrets.
I think that analog solutions to generating sine waves are pretty interesting and cool to study, especially from the perspective of analog computing! However, as you see, generating stable and controllable sine waves is far from trivial. The easiest solution is to use a digital generator. For instance, you can use Mozzi on an Arduino, a Teensy or just pick some μController with either a DAC or without. In the latter case, you need to use PWM to generate the output signal. Mozzi does that for you. Combine this with a filter on the output and you should get a sine wave that is easily controllable. You can now either use a MIDI input on your μController, CV control is also a bit more difficult here but you find people with knowledge about that here on the forum if you want to go this way.
You can check out the MFOS sonic multiplier, it has a sine wave oscillator
I just noticed this in the LM13700 datasheet.
The following accompanying text says Figure 34 but I think they meant 35 (figure 34 uses a single LM13700)
The circuit of Figure 34 employs two LM13700 packages, with three of the amplifiers configured as lo-pass filters and the fourth as a limiter/inverter. The circuit oscillates at the frequency at which the loop phase-shift is 360° or 180° for the inverter and 60° per filter stage. This VCO operates from 5 Hz to 50 kHz with less than 1% THD.
I have build this fixed Sine oscillators bank; it is 8 sine LFOs with differents timing, based on a Wien Bridge circuit. The result is really nice for make drone or for create beautiful sound lanscapes.
(schematic in the build manual, with 3 variants)
Very taken with the sounds on the site but at £105 for the kit (100 more than I ever spend on a module - excluding 3340’s) I’m going to keep looking for a schematic that’s closer to my budget.
I would love to hear more from your build. New to sine wave drones and very interested in combination with wave folder.
Looking at the BOM, there aren’t any expensive parts on it (just everything in octuple ).
And it is completely open-source.
The schematic is in the build guide.
And the source-code package contains the kicad files for the PCBs if you prefer that to stripboard.
Oh I thought you’d bought the kit! I looked on the site link and my old eyes couldn’t find a download of the build file. Any hints?
That’s really excellent documentation.
Does anybody have any resources on the fundamentals of adding CV slash v/oct tracking to an oscillator circuit?
I want a sin sub and haven’t yet found a suitable analog module for this purpose. It does not need something crazy like 10 octaves of tracking, I’m only interested in the two octaves between 40Hz and 150Hz. I suppose an alternative would to be to build a custom quantizer with an Arduino, but that’s much less elegant.
For exponential conversion:
For (linear) voltage controlled sin oscillator:
Many thanks @analogoutput.
Do we have a ‘useful links’ section?
We have the FAQ category so, yes.