# Help with simple sine wave VCO **URL:** \ **Category:** DIY STUFF\ **Created:** [August 25, 2021, 2:01am UTC](https://lookmumnocomputer.discourse.group/t/help-with-simple-sine-wave-vco/3927 "2021-08-25T02:01:54Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Shiro\_pb](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/shiro_pb/32/8576_2.png) [@Shiro\_pb](https://lookmumnocomputer.discourse.group/u/Shiro_pb)\ **Post date:** [August 25, 2021, 2:01am UTC](https://lookmumnocomputer.discourse.group/t/help-with-simple-sine-wave-vco/3927/1 "2021-08-25T02:01:54Z")
So, i’ve been trying to make a simple, cheap and reliable sine wave VCO. And found this one paper with the following VCO It’s a pretty simple build, the output level is self regulating with no additional circuitry, the harmonic distortion is very low and the frequency control is done by a grounded resistor. So it’s exactly what i was looking for! ![image](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/3X/9/1/91f1a3244dae3af10b72a24b9b095c543a7b357e.png) But now i need a method to vary the circled resistance. But the catch here is that this method needs to be highly linear. otherwise, the output won’t be a sine anymore. so far the methods i’ve considered are: a single NPN → it works but it introduces distortion a single jfet → same as above + jfets are more expensive compared with bjts a lm13700 like OTA → it introduced a lot of distortion but i might have messed up with the topology + it’s pretty expensive vactrol → might be the best solution for this case but i’d really really like to use a different solution. so if everything else fails this will be it i’d really appreciate some help paper by: lutz von wangenheim (2002) ---
**Author:** ![analogoutput](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/analogoutput/32/29663_2.png) [@analogoutput](https://lookmumnocomputer.discourse.group/u/analogoutput)\ **Post date:** [August 25, 2021, 2:29am UTC](https://lookmumnocomputer.discourse.group/t/help-with-simple-sine-wave-vco/3927/2 "2021-08-25T02:29:03Z")
Is this for an LFO or an audio oscillator? Do you need accurate 1 V/oct exponential control? Or is less accurate exponential control, or even linear control, good enough? Check this topic if you haven’t: > [@Diy sine wave oscillator](https://lookmumnocomputer.discourse.group/t/diy-sine-wave-oscillator/3478): > > 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. ---
**Author:** ![Shiro\_pb](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/shiro_pb/32/8576_2.png) [@Shiro\_pb](https://lookmumnocomputer.discourse.group/u/Shiro_pb)\ **Post date:** [August 25, 2021, 12:14pm UTC](https://lookmumnocomputer.discourse.group/t/help-with-simple-sine-wave-vco/3927/3 "2021-08-25T12:14:23Z")
Audio oscillator not sure if i’ll need perfect 1v/oct the oscillator is meant for an ondes mardenot like instrument sure, i could use a fully ressonant filter (and if everything else fails i will) but i’d need to modify the circuit to eliminate the inputs and lock the filter into ressonant mode. also add the wave shaping ---
**Author:** ![analogoutput](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/analogoutput/32/29663_2.png) [@analogoutput](https://lookmumnocomputer.discourse.group/u/analogoutput)\ **Post date:** [August 25, 2021, 1:23pm UTC](https://lookmumnocomputer.discourse.group/t/help-with-simple-sine-wave-vco/3927/4 "2021-08-25T13:23:16Z")
Yeah, so presumably you need exponential control even if it’s not necessarily 1.0000 V/oct, and then you probably would want some level of temperature stability even if it’s not necessarily rock steady. A couple discussions: [https://www.schmitzbits.de/expo\_tutorial/](https://www.schmitzbits.de/expo_tutorial/) > **[Exponential converters and how they work](https://northcoastsynthesis.com/news/exponential-converters-and-how-they-work/)** > > Why exponential converters are important in music electronics, and how they work. These provide a control current, how to use that to control your oscillator is the big question. LM13700 is the first thing that comes to my mind. ---
**Author:** ![Shiro\_pb](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/shiro_pb/32/8576_2.png) [@Shiro\_pb](https://lookmumnocomputer.discourse.group/u/Shiro_pb)\ **Post date:** [August 25, 2021, 1:27pm UTC](https://lookmumnocomputer.discourse.group/t/help-with-simple-sine-wave-vco/3927/5 "2021-08-25T13:27:37Z")
that looks good! i was trying to use the circuit in moritz klein’s VCO video i think this might be good ![image](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/3X/2/b/2b43556474bbc16633cb0b63e25513b0662db8d1.png) But the wave keeps shifting upwards with an increase in frequency