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Complete Newb Question about life, the universe, impedance and everything else

Mr. Otto

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This is my first post, I've been hangin' around Midibox for a while now, already started learning electronics and all but it is my first post anyway...

I think I read something about posting rules or something but I couldn't find it again, so please excuse me for some mistakes, and english mistakes too, I'm from Brazil...

First of all I'd like to thank you all for the forum, althou I always thought this is way bigger than a forum, it is a whole community working together for the future of technology spreading...

ok then, first question :

What about impedance? I know MidiBox system works, it works very well, and I know it won't burn my computer if I try to drive Ableton Live with a Midibox64.  But I tried to understand how it really works and I couldn't find more info about impedance, I mean, I know what it is, but I really don't know what to do with it...  Is it something you needed to worry about when designing the pcb's? if so how do you know your computer's impedance? Do you have to match midibox and computer's impedance? or the voltages on a midi signals so low that it really doesn't matter?

It is probably very stupid, but at the same time you could build a simple midibox without ever making yourself that same question since all the design is done, but hey, why not ask?

That's it!

Thank you guys, keep the amazing work...

Mr. Otto

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The short answer is: MIDI is a digital signal transmitted on a current loop, so you do not really have to worry about impedance. The physical layer of that interface is standardized - follow that standard and you are fine (all MIDIbox devices you can find around here are adhering to that standard!).

The long answer is far more complex, you best start looking for Electrical Impedance in Wikipedia.

Best regards, ilmenator

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Apparently it was a very good topic name to get attention.

I will definitely try more of those on better questions, or hopefully, in a few months, news, photos, anyway, proof that I'm on to something, not just asking and never starting s**t...

Well, 3 weeks ago I didn't know what a resistor was, and now I have my own precious soldering iron and a weird noise gen. from musicfromouterspace.com  prototyped on a breadboard! That's fun, my folks think I'm getting crazy though. Too much solder smoke.

Anyway, I think I got what the MIDI standard means. It is supposed to have a opto-isolator on it, so that's why your midibox won't burn your computer or vice-versa...


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Another short answer for you:

As Ilmenator pointed out, MIDI is a digital standard. You do not need to worry about impedance here.

You WILL, however, need to consider impedance on any AUDIO output/input circuitry, such as when you match AUDIO SIGNALS together, or attach them to speakers/headphones.

MBSID is one example of where impedance becomes important. Thankfully, its all there in the circuit diagrams for you. No need to worry.  8)

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