#1007 midimuso midi-cv

It depends on your supply voltage – if it’s good enough to give you ~11.5 V or above, you can use 270 ohm and save a tiny bit of power. If it may drop below that, you may have to use a lower value to make sure the TL431 gets the 1 mA it needs to regulate. See discussion in this thread:

EDIT: 220 ohm is probably better, see here.

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