I ordered the Delfina Flipper. Can anyone tell me what cable(s) I need to buy to connect the audio from the Amiga to the card? Something similar to the CD audio cable?
Yes, exactly. Delfina audio ports are really CD audio ports

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I don't think you'll be able to buy it, but it is trivial to make it. Just connect two RCA connectors to 4-pin CD-Audio plug.