very think's but i have this shematic of DX-4d
sorry but i have DX-4d with 22-4L tascam
this connections are not the same
on my 22-4L tascam, i have 4 connections rca : encoder send
4 connections rca : encoder RCV
4 connections rca : decoder send
4 connections rca : decoder RCV
and 4 connections rca : input
4 connections rca : output