Kimani

Hi guys. Have been reading through the posts but I have an issue may be someone can help. I recently decided to start using SDI cables and my cameras support HDMI. I am using BMD HDMI-SDI converter but my output has a screeching high pitch sound on the right channel while the left channel is clean without any distortion. I am thinking my SDI(300mtr) cable could be mono I don't know what to do.