one of the best passive converters are here:
http://www.bhphotovideo.com/c/product/289843-REG/RDL_RU_LA2D_RULA2D_Bi_Directional_2_Channel.html#specifications
http://www.bhphotovideo.com/c/product/289843-REG/RDL_RU_LA2D_RULA2D_Bi_Directional_2_Channel.html#specifications