# Module requests

**URL:** <https://lookmumnocomputer.discourse.group/t/module-requests/39>\
**Category:** KOSMO MODULES\
**Created:** [January 19, 2020, 2:35pm UTC](https://lookmumnocomputer.discourse.group/t/module-requests/39 "2020-01-19T14:35:13Z")\
**Posts on this page:** 1\
**Showing post:** 191

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**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 30, 2020, 9:57am UTC](https://lookmumnocomputer.discourse.group/t/module-requests/39/191 "2020-05-30T09:57:49Z")

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> [@lookmumnocomputer](#):
>
> whilst im at it. here is the whole schematic. anything else that theoretically shouldn’t work?

First impressions, etc, but looks pretty good to me 😃

I’d consider switching out the opto-coupler circuit for one based on a 6N137, which 1) is faster (guaranteed to be within MIDI specs (\*)), 2) has an actual logic output instead of a transistor, 3) is more widely available (e.g. Tayda has it), and 4) is cheaper, from what I can tell. The circuit I used for the minimachine is [here](https://lookmumnocomputer.discourse.group/t/gameboy-minimachine-aka-mini-megamachine-build-notes/339/2). But this is optional; the 6N138 is used in a ton of DIY MIDI stuff and people would probably have noticed by now if it was all wonky.

And yeah, I still wonder if we cannot come up with a better 10.6 V supply, but that’s for a different subthread 😃

\*) Found some MIDI document that says HP’s 6N138 “have been found acceptable” (which makes me think of [Lemongrab](https://www.youtube.com/results?search_query=lemongrab), not circuit design) but they don’t seem to make it these days and the non-HP 6N138 datasheets I’ve looked at are less convincing, so may depend on manufacturer. The 6N137 is at least 20× faster.

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