you need a DI unit. a passive one should suffice. it should have a stereo cinch/rca input and a stereo cinch/rca output. you're on the safe side if you buy one with an input level switch. this is mine (passive)
i get no distortion at all if i switch it to HIGH.
if you can't find a passive one with any sort of input level adjustment you should probably go for an active one (they obviously need a power source but they're more likely to offer options for input levels).
if you don't want to buy a (new) receiver this is probably the cheapest solution. i'm not going into the technical details behind DI units, they're used for a couple of different things (basically it converts a high impedance level input to low impedance and gets rid of noise, distortion or ground loop hums and similar things in the process).
you can find very cheap ones for $15. you'll likely find many units between $20 and $40. that's still a reasonable price. yes, there are DI units for thousands of dollars - they are not for you.
if you can't find DI units with cinch inputs - search for things like 'stereo signal convertors', 'line splitters', 'line/ground isolators' or similar things. they're basically all DI units - just specifically made/advertised to resolve different issues. as long as there's an option to select the input level you should be fine. getting rid of the distortion/crackling issues is mostly just a secondary 'side effect' with these units anyway.
you can also just use a cinch/rca to jack (phone plug) adapter if you really don't find a unit with cinch inputs.
oh and yeah - it's fairly simple:
connect wii to input, connect receiver/tv to output. select input level (go for the higher settings).
i get no distortion at all if i switch it to HIGH.
if you can't find a passive one with any sort of input level adjustment you should probably go for an active one (they obviously need a power source but they're more likely to offer options for input levels).
if you don't want to buy a (new) receiver this is probably the cheapest solution. i'm not going into the technical details behind DI units, they're used for a couple of different things (basically it converts a high impedance level input to low impedance and gets rid of noise, distortion or ground loop hums and similar things in the process).
you can find very cheap ones for $15. you'll likely find many units between $20 and $40. that's still a reasonable price. yes, there are DI units for thousands of dollars - they are not for you.
if you can't find DI units with cinch inputs - search for things like 'stereo signal convertors', 'line splitters', 'line/ground isolators' or similar things. they're basically all DI units - just specifically made/advertised to resolve different issues. as long as there's an option to select the input level you should be fine. getting rid of the distortion/crackling issues is mostly just a secondary 'side effect' with these units anyway.
you can also just use a cinch/rca to jack (phone plug) adapter if you really don't find a unit with cinch inputs.
oh and yeah - it's fairly simple:
connect wii to input, connect receiver/tv to output. select input level (go for the higher settings).