# HELP! Beginner Question CEM3340 VCO **URL:** \ **Category:** Uncategorized\ **Created:** [March 26, 2020, 12:35pm UTC](https://lookmumnocomputer.discourse.group/t/help-beginner-question-cem3340-vco/444 "2020-03-26T12:35:14Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![aaron2](https://avatars.discourse-cdn.com/v4/letter/a/8e8cbc/32.png) [@aaron2](https://lookmumnocomputer.discourse.group/u/aaron2)\ **Post date:** [March 26, 2020, 12:35pm UTC](https://lookmumnocomputer.discourse.group/t/help-beginner-question-cem3340-vco/444/1 "2020-03-26T12:35:14Z")
Hi, I’m a beginner at DIY electronics so my question is probably pretty stupid. I’m planning on building LMNC’s CEM3340 VCO design and understand most of it apart from a couple of things. If you look at the stripboard layout on his website, he says to connect to the SAW/TRIANGLE OUT/CV IN wires to the ‘tip’ of the corresponding jack. My question is what is the ‘tip of the jack’ actually is as the jack sockets I ordered have three pins. Also, it also says to ‘connect to ground of jack sockets’ on the schematic, which confuses me as to what pin I should connect each of these wires to on each jack socket. Thanks ---
**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:** [March 26, 2020, 12:45pm UTC](https://lookmumnocomputer.discourse.group/t/help-beginner-question-cem3340-vco/444/2 "2020-03-26T12:45:34Z")
Depends on the jack. The extra pin is probably a switch but there are many configurations (see [this post](https://lookmumnocomputer.discourse.group/t/can-i-add-1-4-jacks-to-this-eurorack-module/371/6) for some examples, and the linked document there for many more) and no standard pinout even if you’ve identified the jack type. Do you have a datasheet for the jack you’re using? Otherwise, plug in a cable and use your multimeter’s continuity tester to figure out what’s connected to what pin. ---
**Author:** ![aaron2](https://avatars.discourse-cdn.com/v4/letter/a/8e8cbc/32.png) [@aaron2](https://lookmumnocomputer.discourse.group/u/aaron2)\ **Post date:** [March 26, 2020, 12:49pm UTC](https://lookmumnocomputer.discourse.group/t/help-beginner-question-cem3340-vco/444/3 "2020-03-26T12:49:28Z")
frederik The jack is a 1/4" jack and is one of these: [https://www.rapidonline.com/bkl-1109034-jack-socket-6-35-mm-3-pin-stereo-50-1499](https://www.rapidonline.com/bkl-1109034-jack-socket-6-35-mm-3-pin-stereo-50-1499) Hope this helps understand what I’m trying to find out. thanks ---
**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:** [March 26, 2020, 12:55pm UTC](https://lookmumnocomputer.discourse.group/t/help-beginner-question-cem3340-vco/444/4 "2020-03-26T12:55:30Z")
If you click on the “Data sheets” tab there’s a link to this datasheet: > **[732800\_da\_en\_01.pdf](https://static.rapidonline.com/pdf/732800_da_en_01.pdf)** > > 1699.59 KB … which unfortunately doesn’t answer your question. It just shows the dimensions of the thing, no footprint and no explanation of the electrical connections. Sorry about that. Sometimes datasheets are more helpful than that. So your best bet as @fredrik said is: plug a cable into it and use a multimeter on the connectivity setting to see which connector goes to the tip of the opposite plug and which goes to ground (the sleeve of the plug). ---
**Author:** ![sketchie](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/sketchie/32/144_2.png) [@sketchie](https://lookmumnocomputer.discourse.group/u/sketchie)\ **Post date:** [March 26, 2020, 1:01pm UTC](https://lookmumnocomputer.discourse.group/t/help-beginner-question-cem3340-vco/444/5 "2020-03-26T13:01:42Z")
I’ve run out of “likes” so i’ll just say “I like this post!” 🙃 👍 🤪 ---
**Author:** ![Caustic](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/caustic/32/15588_2.png) [@Caustic](https://lookmumnocomputer.discourse.group/u/Caustic)\ **Post date:** [March 26, 2020, 5:43pm UTC](https://lookmumnocomputer.discourse.group/t/help-beginner-question-cem3340-vco/444/6 "2020-03-26T17:43:55Z")
If you can, take a pic of your sockets if you like just to be sure. 🙂 Don’t worry about asking questions we like that here. If you have a multimeter, you can run a continuity test on the inside of the barrel part and touch the bits to see. If you don’t know wtf I’m talking about that’s fine, if you need more explanation we can do so.