I made a MIDI in/out circuit, which works, however, I see I have some changes compared to some other circuits I see.
In the official documentation Midi Org I see two resistors on the MIDI out circuit, both 220 ohm. I'm sure I only use one (but I'm not at home, so I cannot check which one I might miss). But so far I didn't get any problems (but never tested in a 'noisy' environment.
In the same scheme, there are 2 inverters (I think), the triangle, one without an A and one with. I also don't use that. I think it's for keeping a steady 0 or 5 V signal, so I think it's good to add. Now I see in some other circuits (randomly from google search with pics), a 74LS04, or 74LS14 or others. At home I have some 74LS14's (Schmitt Trigger hex inverter), but I also read those are for processing signals (like MIDI I guess), but can be slow. So I am not sure what to use, 7404 or 7414? I see also a lot of schemes with 7414's so I guess these are ok.
For the thru I see the same ... does one triangle without and one with A means, I need 2 inverters after each other? Probably it is. Since I want to use 3 MIDI In/Out/Thru's, would that mean 2 (per out or thru) * 2 (out + thru) * 3 (# 3 in/out/thrus) = 12 hex inverters (meaning 2 ICs?); see also item 6
In this circuit, DSS306 are used. I cannot find them on aliexpress, but also they are not in the official MIDI org circuit. Are they needed ... or better (and why)?
In this circuit, transistors are used (2N2222) ... yet another solution (?) What is the advantage? (btw, I plan using BC337's since I have those and are similar, at least if there is a clear advantage).
Also it mentions about the hex inverter, which I probably do not need for the MIDI Out (since it comes from the Arduino, not sure if the Arduino handles this), but for the MIDI Thru I want to connect it directly from the MIDI In. Is that assumption correct? (better use it for both MIDI Out and Thru?)
Thanks if you can help me with one or more of the above questions.