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you need one of this Stereo Pot: (VR4 in the 303)
all other values are available from Musikding, tayda, banzai, thonk and many more.
VR4 B50K Stereo !!
VR2, VR7 = 50KB
V3, VR5 =50KA
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in total 6 potentiometers
https://www.thonk.co.uk/shop/alpha-9mm-pots-vertical-t18/
and you need:
pinstripes as shown above in my pictures.
2x 3.5mm (1/8inch) stereo jacks Lumberg KLB-4 which is available worldwide in hundreds of shops - its a quality part.
2x Adapter for the Midi holes to use the 3.5mm jacks - ONLY if you use the RE-303 Aluminum case - this are included with the PCB order in my shop !
2x 3.5mm (1/8 inch) plug to MIDI Cable - thonk or make your own.. https://www.thonk.co.uk/shop/alm-midi-trs-cable/ or DIY: NYS322 + 172-7435-E (mouser)
update 01/2020: ground the MIDI IN port too, that's needed because the acrylic's adapter to the stereo 3.5mm jacks are isolated
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