The one round/one squared configuration is a polarized connection. What would work is a non-polarized cable with a connector that has both sides rounded. Here is a good example:
http://www.oyaide.com/e_audio/audio_products_files/li15dpc.htm
alan m. kafton
audio excellence az
http://www.oyaide.com/e_audio/audio_products_files/li15dpc.htm
alan m. kafton
audio excellence az