[Melodica-Me]

Hi Olivier, there are three ways, you can use a in-line transformer about $10-$20 bucks. you connect the cord from your melodica to the inline transformer then from the transformer to your amplifier so you will need two cords. the next is to use a clean boost pedal. This one has a bass and treble boost which is nice to have.

https://www.ebay.com/itm/New-Mooer-Pure-Boost-Clean-Boost-Micro-Guitar-Effects-Pedal/112437833598?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D20131003132420%26meid%3Dad62b391915b49a68066687d7b8d1ae7%26pid%3D100005%26rk%3D4%26rkt%3D12%26sd%3D261579478720%26itm%3D112437833598&_trksid=p2047675.c100005.m1851

Connection is the same as the inline transformer. These pedals are much more expensive $50-200. and the last is a D.I. “Direct Input” box this is the same as a clean boost. these usually have a low impedance out as well which is nice for recording. This method works best for me when I use the Hammond Melodeon. Speaking of recording, I personally do not like the built in pick up for recording, it does not represent what the melodica actually sounds like. I use a microphone for a natural sound. I use a pedal board for effects and do use the built in pick up for that but mike my amplifier. I can go directly from the pedal board to the IA converter for recording which works great.
Hope this Helps
Melodica-Me