Question about the x0x midi thru design

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altitude
 
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Question about the x0x midi thru design

Post by altitude »

I need to make some form of thru port for my 3030s and I noticed that the x0x design only consists of a transistor. Can someone elaborate on this design? Better than a 74HC14 buffer? I literally need to split a midi signal to two TM3030 boards powered from the same PSU from one midi port so the simpler the better. The 3030 uses an active optocoupler if that makes any difference

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Re: Question about the x0x midi thru design

Post by guest »

the midi in should have an optoisolator
but after that
the thrus can just use any buffer
so a transistor or 74hc14 is fine
no real difference between them

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altitude
 
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Re: Question about the x0x midi thru design

Post by altitude »

so any PNP transistor will do? Any modification from the schematic?

thanx

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Re: Question about the x0x midi thru design

Post by guest »

what are you driving the midi thru with
will it be coming directly from the optoisolator
or will it be coming from a microcontroller

you can use an npn transistor
and two 220ohm resistors
as shown on the schematic
but if youre driving it with a microcontroller pin
you can use a 10k resistor to the base
with another 10k from base to ground

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altitude
 
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Re: Question about the x0x midi thru design

Post by altitude »

guest wrote:what are you driving the midi thru with
will it be coming directly from the optoisolator
or will it be coming from a microcontroller

you can use an npn transistor
and two 220ohm resistors
as shown on the schematic
but if youre driving it with a microcontroller pin
you can use a 10k resistor to the base
with another 10k from base to ground

It will be out of the opto coupler. I'll give that a whirl and report back.

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Re: Question about the x0x midi thru design

Post by guest »

depending upon the optoisolator
it may not be able to drive more than one transistor

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altitude
 
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Re: Question about the x0x midi thru design

Post by altitude »

its an active 6n138

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Re: Question about the x0x midi thru design

Post by guest »

in that case
just connect the base up to the output of the optocoupler
and dont use the 10k resistors
it should be able to handle a few transistors

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altitude
 
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Re: Question about the x0x midi thru design

Post by altitude »

Sorry, this is not sinking in for some reason.

Do I just branch the output of the opto one to the PIC and the other to the transistor for the buffer? Or do I need to place the transistor in the path of the TTL line and then branch it after the transistor like in the I/O board schematic?

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Re: Question about the x0x midi thru design

Post by guest »

copy the ioboard schematic
except dont use the 100ohm resistor
and maybe change r17 to 5.6k or similar

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altitude
 
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Re: Question about the x0x midi thru design

Post by altitude »

So cut the trace?

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Re: Question about the x0x midi thru design

Post by guest »

if youre using a x0x ioboard
you can just use it without changing anything

otherwise if youre populating a new board
and using the 6n138
just dont stuff the 100ohm resistor

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phono
 
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Re: Question about the x0x midi thru design

Post by phono »

you can build a midi thru box quite easily

i built this one on breadboard, works a charm

http://m.bareille.free.fr/midithrubox/midithrubox.htm

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altitude
 
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Re: Question about the x0x midi thru design

Post by altitude »

I don't think I explained exactly what I have in mind.. I have two synths that don't have through ports that I want to drive with one Midi input so I am trying to add a through port to one of them. Both are built..

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Re: Question about the x0x midi thru design

Post by phono »

yes this schematic will do exactly that, you could adapt it quite easily to take a midi in and split to as many throughs as needed

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