# Contemplating the circuitbenders drumBs **URL:** \ **Category:** DIY STUFF\ **Created:** [January 24, 2021, 3:00pm UTC](https://lookmumnocomputer.discourse.group/t/contemplating-the-circuitbenders-drumbs/2771 "2021-01-24T15:00:34Z")\ **Posts on this page:** 18\ **Page:** 3
**Author:** ![sebastian](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/sebastian/32/39_2.png) [@sebastian](https://lookmumnocomputer.discourse.group/u/sebastian)\ **Post date:** [May 14, 2021, 8:45am UTC](https://lookmumnocomputer.discourse.group/t/contemplating-the-circuitbenders-drumbs/2771/41 "2021-05-14T08:45:51Z")
No reason! Thank you for spotting that! ---
**Author:** ![sebastian](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/sebastian/32/39_2.png) [@sebastian](https://lookmumnocomputer.discourse.group/u/sebastian)\ **Post date:** [May 14, 2021, 8:40pm UTC](https://lookmumnocomputer.discourse.group/t/contemplating-the-circuitbenders-drumbs/2771/42 "2021-05-14T20:40:09Z")
Speaking of VCAs, any idea why I have these little spikes in the (simulated) VCA output? Green is input, red is out. I do not have them if I put the signal through a filter. ![Screenshot from 2021-05-14 22-37-11](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/9/924af669044cf8a83b3b4531a30c12b1284ae3c8.png) ---
**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 15, 2021, 2:02pm UTC](https://lookmumnocomputer.discourse.group/t/contemplating-the-circuitbenders-drumbs/2771/43 "2021-05-15T14:02:21Z")
> [@sebastian](#): > > Oh, and I want to change the power section to use diodes as well, but I need to check how to do that again I too want to start putting diodes on my power supplies, and I had a look at how befaco do theirs: > **[Slew\_Limiter\_V1\_2\_Schematic.pdf](https://befaco.org/docs/Slew_Limiter/Slew_Limiter_V1_2_Schematic.pdf)** > > 26.80 KB There’s a BOM file where it says D1,D2 are 1N5817 - which are Schottky diodes with low Vf, the datasheet quotes they are intended for polarity protection among other things. I have’t built or tried mine yet, but I figured if it doesn’t work I can just short them out on the board and just continue to live life on the edge with unprotected supplies. Cheers ---
**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 15, 2021, 2:11pm UTC](https://lookmumnocomputer.discourse.group/t/contemplating-the-circuitbenders-drumbs/2771/44 "2021-05-15T14:11:44Z")
> [@sebastian](#): > > Speaking of VCAs, any idea why I have these little spikes in the (simulated) VCA output? Green is input, red is out. I do not have them if I put the signal through a filter. I’m just guessing, but there is probably some input capacitance inside the model of your VCA. If you drive those caps with instantaneous edges, like in your square wave, perhaps the simulation will have them overshoot. Try with a square wave that has some non-zero rise time, even a couple of ns might make a difference. Cheers ---
**Author:** ![fredrik](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/fredrik/32/682_2.png) [@fredrik](https://lookmumnocomputer.discourse.group/u/fredrik)\ **Post date:** [May 15, 2021, 2:13pm UTC](https://lookmumnocomputer.discourse.group/t/contemplating-the-circuitbenders-drumbs/2771/45 "2021-05-15T14:13:37Z")
That’s the “series diodes” option here: > [@Typical module power circuit](https://lookmumnocomputer.discourse.group/t/typical-module-power-circuit/1134/3): > > Different schools: 10 ohm and capacitor near power header (this basically results in an RC low pass filter, but with a voltage drop over the resistor depending on the current). Usually somewhat pointless (the resistors, not necessarily the capacitors). 10 ohm without capacitors (either using them as fuses, expecting them to die if something’s shorted, or possibly just cargo culting, trying to do the above but forgetting how things work, see “power sins” [here](https://northcoastsynthesis.com/news/design-mistakes-in-synth-schematics/) for more). Ferrite beads (if done … (I prefer diodes to ground myself, but that assumes that you only use power supplies that can deal with a short.) ---
**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 15, 2021, 2:24pm UTC](https://lookmumnocomputer.discourse.group/t/contemplating-the-circuitbenders-drumbs/2771/46 "2021-05-15T14:24:31Z")
I use series 1N5817 like that all the time. No problems. Then again I use shrouded headers and I don’t think I’ve ever connected power backwards on an assembled module. (On an [IC on a breadboard](https://lookmumnocomputer.discourse.group/t/a-litany-of-dumbassery/526/312), not so much.) ---
**Author:** ![sebastian](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/sebastian/32/39_2.png) [@sebastian](https://lookmumnocomputer.discourse.group/u/sebastian)\ **Post date:** [May 16, 2021, 10:55am UTC](https://lookmumnocomputer.discourse.group/t/contemplating-the-circuitbenders-drumbs/2771/47 "2021-05-16T10:55:47Z")
Interesting, i will try it, thanks! 🙂 Something else: is it enough to use a single pin for +12V -12V and 0V/GND each for the interconnection? ![Screenshot from 2021-05-16 12-53-11](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/f/fa2c3ef1b5fca40e4e0b83eebb2bcfd07889f7c5.png) ![Screenshot from 2021-05-16 12-53-15](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/f/f42784b40e90a973c4950483485bfb2f21475f18.png) ---
**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 16, 2021, 11:10am UTC](https://lookmumnocomputer.discourse.group/t/contemplating-the-circuitbenders-drumbs/2771/48 "2021-05-16T11:10:39Z")
I tend to put GND on all the connectors I can. Nothing empirical behind it, but I figure you want your ground plane connected in as many places as possible: I don’t need -12V on my latest front panel, but here’s what I did. Front Panel: ![image](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/d/d0eb60478ab0579229270c5434b944b01e5c4cc7.png) Which connects to the Back Panel (Brains!): ![image](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/1/1baf6c050c44cf5856e33ec8b5889ad116dbf1a7.png) ---
**Author:** ![sebastian](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/sebastian/32/39_2.png) [@sebastian](https://lookmumnocomputer.discourse.group/u/sebastian)\ **Post date:** [June 18, 2021, 9:45pm UTC](https://lookmumnocomputer.discourse.group/t/contemplating-the-circuitbenders-drumbs/2771/49 "2021-06-18T21:45:15Z")
I am making progress! Noise circuit works, oscillator works! Still missing parts for the mixer and the filter. I made a stupid mistake in kicad and swapped +12V and -12V for one of the TL074 (postet in the litany thread already), but let’s see if I can fix it! 😅 ![platine4](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/c/c83b5681fc63492d82b1b0d817463ca5f4791bfd.jpeg) ![comet](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/f/f1f584a6b7dabf7a13a8b87471b972b73870d92e.jpeg) ---
**Author:** ![CTorp](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/ctorp/32/15023_2.png) [@CTorp](https://lookmumnocomputer.discourse.group/u/CTorp)\ **Post date:** [June 19, 2021, 1:43am UTC](https://lookmumnocomputer.discourse.group/t/contemplating-the-circuitbenders-drumbs/2771/50 "2021-06-19T01:43:56Z")
Looks great! I want it! ---
**Author:** ![sebastian](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/sebastian/32/39_2.png) [@sebastian](https://lookmumnocomputer.discourse.group/u/sebastian)\ **Post date:** [June 20, 2021, 6:59pm UTC](https://lookmumnocomputer.discourse.group/t/contemplating-the-circuitbenders-drumbs/2771/51 "2021-06-20T18:59:54Z")
I will of course make the files available, but I would rather wait till I have tested it 🙂 I already found that I mixed up the power on one Tl074 and the pots for mixing, decay and probably the attenuverters are the wrong way 😫 I am still waiting for parts to test the filter and vca and all together. ---
**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:** [June 20, 2021, 7:04pm UTC](https://lookmumnocomputer.discourse.group/t/contemplating-the-circuitbenders-drumbs/2771/52 "2021-06-20T19:04:52Z")
> [@sebastian](#): > > and the pots for mixing, decay and probably the attenuverters are the wrong way Who has two thumbs and [does this on a regular basis](https://lookmumnocomputer.discourse.group/t/a-litany-of-dumbassery/526/537)? (Of course I checked them before having the PCBs made. And they were right. For certain values of right. Namely wrong.) ---
**Author:** ![Sonosus](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/sonosus/32/13679_2.png) [@Sonosus](https://lookmumnocomputer.discourse.group/u/Sonosus)\ **Post date:** [June 20, 2021, 7:07pm UTC](https://lookmumnocomputer.discourse.group/t/contemplating-the-circuitbenders-drumbs/2771/53 "2021-06-20T19:07:52Z")
Aargh dammit! You had me thinking - I checked and sure enough the pots on the Superspreader are the wrong way. ![image](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/d/d215e81d038d7835d4b5ea9c2b91e7084f210fbc.png) That is wrong isn’t it? ---
**Author:** ![eric](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@eric](https://lookmumnocomputer.discourse.group/u/eric)\ **Post date:** [June 20, 2021, 7:48pm UTC](https://lookmumnocomputer.discourse.group/t/contemplating-the-circuitbenders-drumbs/2771/54 "2021-06-20T19:48:22Z")
I’d say… it depends 🙂 It’s called CV ATT(enuation), so the more you turn it to the right, the more it attenuates… Seems right to me, even if I find it more natural the wrong way 🙂 ---
**Author:** ![sebastian](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/sebastian/32/39_2.png) [@sebastian](https://lookmumnocomputer.discourse.group/u/sebastian)\ **Post date:** [August 4, 2021, 7:50pm UTC](https://lookmumnocomputer.discourse.group/t/contemplating-the-circuitbenders-drumbs/2771/55 "2021-08-04T19:50:54Z")
I have fixed a few issues now, but more remain. One is that I have a bleed of the envelope in the output. So, I always have a click sound even when I turn down vco and noise completely ☹ It’s around 1V , the envelope max is around 10V I think. Anyone got an idea what can cause this bleed? ---
**Author:** ![CTorp](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/ctorp/32/15023_2.png) [@CTorp](https://lookmumnocomputer.discourse.group/u/CTorp)\ **Post date:** [August 4, 2021, 11:18pm UTC](https://lookmumnocomputer.discourse.group/t/contemplating-the-circuitbenders-drumbs/2771/56 "2021-08-04T23:18:37Z")
Sounds like what happens with the k25 EG, although a bit worse. Which envelope circuit are you using now? ---
**Author:** ![sebastian](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/sebastian/32/39_2.png) [@sebastian](https://lookmumnocomputer.discourse.group/u/sebastian)\ **Post date:** [August 5, 2021, 6:49am UTC](https://lookmumnocomputer.discourse.group/t/contemplating-the-circuitbenders-drumbs/2771/57 "2021-08-05T06:49:25Z")
I am using this one, which is from Barton bmc018: Edit: Not Barton, it’s Barton + electricdruid ([Design a Eurorack “Vintage VCA” with the LM13700 – Electric Druid](https://electricdruid.net/design-a-eurorack-vintage-vca-with-the-lm13700/)) ![Screenshot from 2021-08-05 08-47-28](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/3X/c/7/c7eafa07a7d882fb348f4b1c1ebbe7cdcdee16eb.png) I will look for the k25 EG thread. Could you solve it there? ---
**Author:** ![sebastian](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/sebastian/32/39_2.png) [@sebastian](https://lookmumnocomputer.discourse.group/u/sebastian)\ **Post date:** [August 5, 2021, 10:40am UTC](https://lookmumnocomputer.discourse.group/t/contemplating-the-circuitbenders-drumbs/2771/58 "2021-08-05T10:40:33Z")
Sorry I noticed that I did not describe that well! The envelope itself seems okay, it goes back to zero as expected. the problem is that it somehow gets into the (audio) output. So I suspect the VCA (that’s why I posted the circuit of that and not of the envelope). Even when there is no (audio) input at the VCA, as soon as the envelope comes in (at the VCA CV), it comes out of the output (scaled down to 1V max, but still). It is as if there was a 1V constant signal at the VCA input, but I measure 0V there… [Previous page](https://lookmumnocomputer.discourse.group/t/contemplating-the-circuitbenders-drumbs/2771.md?page=2)