If you remove the jumper when not in AY mode, you'll be sure there won't be extra noise from the Atmega8 chip. J1: extra midi input GND (below) and midi wire nb 5 if you don't want to use the DIN5 ...

Then, solder stranded wire to J2 and connect them to pins 4 and 5 of a female chassis mount DIN-5 connector for MIDI input. It is also possible to mount a USB connection to the exterior of the DR-110 ...