# Of volca samples, pajens, arduinos and midi

**URL:** <https://lookmumnocomputer.discourse.group/t/of-volca-samples-pajens-arduinos-and-midi/4240>\
**Category:** DIY STUFF\
**Created:** [November 17, 2021, 6:26pm UTC](https://lookmumnocomputer.discourse.group/t/of-volca-samples-pajens-arduinos-and-midi/4240 "2021-11-17T18:26:21Z")\
**Posts on this page:** 1\
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**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:** [November 17, 2021, 11:37pm UTC](https://lookmumnocomputer.discourse.group/t/of-volca-samples-pajens-arduinos-and-midi/4240/6 "2021-11-17T23:37:24Z")

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There are better optoisolators for MIDI than the 6N138:

> [@Module requests](https://lookmumnocomputer.discourse.group/t/module-requests/39/62):
>
> 6N138 is [a JEDEC part code](https://en.wikipedia.org/wiki/JEDEC) so they all have the same basic specs. Just grab one in the right package (DIP/PDIP for through hole, not SMD). Note that 6N138 appears in a lot of internet schematics, but strictly speaking it’s not fast enough to match the MIDI spec requirements, even if that probably doesn’t matter for normal use. (I use 6N137 instead, which is much faster, has a logic gate output instead of a darlington transistor which is nice since you’re connecting it to a logic gate input, an…

I’ve breadboarded with an H11L1 and it worked, but I went with 6N137 in my MIDI-CV module. The circuit’s a little different from the 6N138. I used:

![image](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/3X/c/5/c5c181e7675713a722a6ef8841bb191bfe66824d.png)

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