# My build progress **URL:** \ **Category:** DIY STUFF\ **Created:** [March 1, 2020, 8:57pm UTC](https://lookmumnocomputer.discourse.group/t/my-build-progress/345 "2020-03-01T20:57:53Z")\ **Posts on this page:** 20\ **Page:** 246
**Author:** ![BlackDeath](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/blackdeath/32/7644_2.png) [@BlackDeath](https://lookmumnocomputer.discourse.group/u/BlackDeath)\ **Post date:** [May 29, 2022, 9:57am UTC](https://lookmumnocomputer.discourse.group/t/my-build-progress/345/4928 "2022-05-29T09:57:02Z")
> [@TimMJN](#): > > 5 VCAs This is crazy! Is this for a module or a stand-alone device? Why 5 VCAs? ---
**Author:** ![TimMJN](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/timmjn/32/15227_2.png) [@TimMJN](https://lookmumnocomputer.discourse.group/u/TimMJN)\ **Post date:** [May 29, 2022, 10:03am UTC](https://lookmumnocomputer.discourse.group/t/my-build-progress/345/4929 "2022-05-29T10:03:40Z")
I’m planning to make it a module, probably quite a beefy one, 20cm at the least. The SS2130 has a 5-channel current-controlled mixer on board, basically 5 VCAs with their outputs summed. I’m additionally putting attenuverters on their control inputs to enable cross-fading between waveforms etc. ---
**Author:** ![Dave](https://avatars.discourse-cdn.com/v4/letter/d/ee7513/32.png) [@Dave](https://lookmumnocomputer.discourse.group/u/Dave)\ **Post date:** [May 29, 2022, 5:32pm UTC](https://lookmumnocomputer.discourse.group/t/my-build-progress/345/4930 "2022-05-29T17:32:58Z")
Looking good, this is going to be one beefy module, I was trying to look at your schematic earlier, but was hindered by the resolution. I am hoping you have a spare board when you are done. 🙂 ---
**Author:** ![TimMJN](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/timmjn/32/15227_2.png) [@TimMJN](https://lookmumnocomputer.discourse.group/u/TimMJN)\ **Post date:** [May 29, 2022, 6:01pm UTC](https://lookmumnocomputer.discourse.group/t/my-build-progress/345/4931 "2022-05-29T18:01:33Z")
> [@Dave](#): > > hindered by the resolution I have to admit that was done entirely on purpose… the full version will be up once everything is tried and tested! 😁 ---
**Author:** ![Jos](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/jos/32/151_2.png) [@Jos](https://lookmumnocomputer.discourse.group/u/Jos)\ **Post date:** [May 29, 2022, 10:03pm UTC](https://lookmumnocomputer.discourse.group/t/my-build-progress/345/4932 "2022-05-29T22:03:53Z")
What does the FET do? ---
**Author:** ![TimMJN](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/timmjn/32/15227_2.png) [@TimMJN](https://lookmumnocomputer.discourse.group/u/TimMJN)\ **Post date:** [May 30, 2022, 4:45am UTC](https://lookmumnocomputer.discourse.group/t/my-build-progress/345/4933 "2022-05-30T04:45:59Z")
It switches the oscillator direction to allow for through-zero FM ---
**Author:** ![jaradical](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/jaradical/32/12069_2.png) [@jaradical](https://lookmumnocomputer.discourse.group/u/jaradical)\ **Post date:** [May 30, 2022, 2:52pm UTC](https://lookmumnocomputer.discourse.group/t/my-build-progress/345/4934 "2022-05-30T14:52:58Z")
Got some PWM working on this Blackpill: [[Album] Blackpill PWM test ![](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/3X/f/5/f5dbb3b447d1341d1467c4e2552e10c0eb874864.jpeg "Blackpill PWM test") ](https://imgur.com/a/K1EBc4w) Getting decent audio out of it might be a challenge though… ---
**Author:** ![hitachii](https://avatars.discourse-cdn.com/v4/letter/h/b5ac83/32.png) [@hitachii](https://lookmumnocomputer.discourse.group/u/hitachii)\ **Post date:** [May 30, 2022, 3:05pm UTC](https://lookmumnocomputer.discourse.group/t/my-build-progress/345/4935 "2022-05-30T15:05:59Z")
the Mutable Instruments Shruthi uses PWM for both for 8 bit audio and for control voltage! ---
**Author:** ![jaradical](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/jaradical/32/12069_2.png) [@jaradical](https://lookmumnocomputer.discourse.group/u/jaradical)\ **Post date:** [May 30, 2022, 3:12pm UTC](https://lookmumnocomputer.discourse.group/t/my-build-progress/345/4936 "2022-05-30T15:12:53Z")
Yeah - I have a Tubeohm version - I’ll have a dig through the code / schematic to try and figure out what’s going on there. I started out with12 bit first, but I think the RC filter needed to get rid of the ripple makes the whole thing very slow. There are some tricks for summing multiple fewer bit PWM channels though - to be investigated… ---
**Author:** ![hitachii](https://avatars.discourse-cdn.com/v4/letter/h/b5ac83/32.png) [@hitachii](https://lookmumnocomputer.discourse.group/u/hitachii)\ **Post date:** [May 30, 2022, 3:23pm UTC](https://lookmumnocomputer.discourse.group/t/my-build-progress/345/4937 "2022-05-30T15:23:58Z")
i never tried summing but I’ve seen people passionately arguing over its efficacy which always makes it worth a shot haha. been wanting to try it on [Teensy 4.1](https://www.pjrc.com/teensy/td_pulse.html), which can do 12 bit resolution at ~40kHz. ---
**Author:** ![hitachii](https://avatars.discourse-cdn.com/v4/letter/h/b5ac83/32.png) [@hitachii](https://lookmumnocomputer.discourse.group/u/hitachii)\ **Post date:** [May 30, 2022, 5:42pm UTC](https://lookmumnocomputer.discourse.group/t/my-build-progress/345/4938 "2022-05-30T17:42:53Z")
[Dave Brown’s adaptation of Marc Bareille’s version of Vladimir Kuzmin’s Polivoks VCF](http://xpmtl.net/sdiy/projects/polivoks-vcf/). so far minus the costly Spectrol 149 pots wow. and tuning, haven’t given it a proper tune yet. This thing sounds nasty. absolutely vile. Putrescence the likes of which Baron Harkonnen would applaud. I’m in love. [![](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/3X/f/1/f1cb07ca185b0f1bb74df27433ed02b5455c1613.jpeg "Поливокс VCF test") ](https://www.youtube.com/watch?v=ret5lHv60Rk) i intend to add CV resonance, using the OTA portion of the following design. No worries with the extra half of the LM13700, i like doing things in pairs. however i have heard tell that this configuration would affect the audio in the resonance path. anyone have experience with this? Alternately i was thinking an opto isolator, transistor based if that works any better. ![Add CV to any pot](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/3X/5/f/5f031d05603bccf9c979de8dfac4e62b4ec409ed.jpeg) ---
**Author:** ![jaradical](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/jaradical/32/12069_2.png) [@jaradical](https://lookmumnocomputer.discourse.group/u/jaradical)\ **Post date:** [May 30, 2022, 6:47pm UTC](https://lookmumnocomputer.discourse.group/t/my-build-progress/345/4939 "2022-05-30T18:47:23Z")
I used something like that in my diode ladder filter: ![image](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/3X/6/e/6e64bc1aeafde9ea3363ce8b0f5bec699ebf956d.png) It works okay - the resonance is pretty harsh and whistley - but I guess that just adds character. Cheers ---
**Author:** ![hitachii](https://avatars.discourse-cdn.com/v4/letter/h/b5ac83/32.png) [@hitachii](https://lookmumnocomputer.discourse.group/u/hitachii)\ **Post date:** [May 30, 2022, 7:30pm UTC](https://lookmumnocomputer.discourse.group/t/my-build-progress/345/4940 "2022-05-30T19:30:44Z")
Thanks for the tip! Will look into this. Gotta give it a try and see if it passes the taste test. ---
**Author:** ![Bpbby](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/bpbby/32/15259_2.png) [@Bpbby](https://lookmumnocomputer.discourse.group/u/Bpbby)\ **Post date:** [May 30, 2022, 8:01pm UTC](https://lookmumnocomputer.discourse.group/t/my-build-progress/345/4941 "2022-05-30T20:01:23Z")
Cant you/we (i am looking jnto this as well) use a normal VCA type circuit ? Something that would define how much is going into the resonance loop … often that is what the resonnance pot is doing. ---
**Author:** ![knopsl](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/knopsl/32/23478_2.png) [@knopsl](https://lookmumnocomputer.discourse.group/u/knopsl)\ **Post date:** [May 30, 2022, 8:03pm UTC](https://lookmumnocomputer.discourse.group/t/my-build-progress/345/4942 "2022-05-30T20:03:16Z")
when will the module documentation be available on github/wordpress? 🙂 ---
**Author:** ![jaradical](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/jaradical/32/12069_2.png) [@jaradical](https://lookmumnocomputer.discourse.group/u/jaradical)\ **Post date:** [May 30, 2022, 8:19pm UTC](https://lookmumnocomputer.discourse.group/t/my-build-progress/345/4943 "2022-05-30T20:19:43Z")
I built my VCA using LM13700’s - it’s more or less what this bit of circuitry is doing. ---
**Author:** ![Jos](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/jos/32/151_2.png) [@Jos](https://lookmumnocomputer.discourse.group/u/Jos)\ **Post date:** [May 30, 2022, 9:35pm UTC](https://lookmumnocomputer.discourse.group/t/my-build-progress/345/4944 "2022-05-30T21:35:33Z")
In the right hand picture in Method 2, the capacitor attached to the A and B resistors is something I would not expect. Including that in the circuit would only allow changes in CV to do something. But what about constant values? Have you tried this particular or any of the other methods? ---
**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:** [May 30, 2022, 10:34pm UTC](https://lookmumnocomputer.discourse.group/t/my-build-progress/345/4945 "2022-05-30T22:34:27Z")
It is there, link is in this post > [@Barton Musical Circuits BMC021 Full Wave Dual Rectifier](https://lookmumnocomputer.discourse.group/t/barton-musical-circuits-bmc021-full-wave-dual-rectifier/5020): > > This is the Barton Musical Circuits BMC021 Full Wave Dual Rectifier in Kosmo format, with some modifications. It’s a kind of wavefolder, taking the input signal, adding a variable DC bias, and rectifying the result. I built it using the BMC circuit board mounted behind a Kosmo format fabricated FR4 front panel. (I had some [difficulties](https://lookmumnocomputer.discourse.group/t/my-build-lack-of-progress/1419/66) but none particular to this design.) I did make some changes. As usual with Barton modules, I used 100 nF instead o… ---
**Author:** ![hitachii](https://avatars.discourse-cdn.com/v4/letter/h/b5ac83/32.png) [@hitachii](https://lookmumnocomputer.discourse.group/u/hitachii)\ **Post date:** [May 30, 2022, 10:40pm UTC](https://lookmumnocomputer.discourse.group/t/my-build-progress/345/4946 "2022-05-30T22:40:00Z")
i haven’t tried that method, no. I’ve made a crude vactrol circuit a few times but the result was unsatisfactory. i may try it out and will let you know if i do! supposing i remove the cap to allow constant voltage, would it break functionality elsewhere in the circuit? (sorry I’m still very amateurish) ---
**Author:** ![devicex](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/devicex/32/28_2.png) [@devicex](https://lookmumnocomputer.discourse.group/u/devicex)\ **Post date:** [May 30, 2022, 11:48pm UTC](https://lookmumnocomputer.discourse.group/t/my-build-progress/345/4947 "2022-05-30T23:48:15Z")
![20220530_1923451](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/3X/5/9/5959b894948414e74e703023f8389c8d6e54c4f3.jpeg) working on cases for a friend with some help . [Previous page](https://lookmumnocomputer.discourse.group/t/my-build-progress/345.md?page=245) [Next page](https://lookmumnocomputer.discourse.group/t/my-build-progress/345.md?page=247)