fitted new head unit. help please

[s3welshy]

Hi all I just fitted a pioneer deh4500. Into my 1999 s3.
I bought an adapter cable from halfords which says its for audi rear amplified. Ive installed it and im only getting sound out of the rear speakers, theres also a high pitch squeal when the volumes low.
My s3 has the bose system installed.
Any ideas?

Thanks again.

 

[A3-Lee]

You need the lead for fully amplified mate the lead you have is wrong mate

 

[s3welshy]

Thought so.
Cheers mate