You could always use a phono pre-amp to convert the phono signal from your 3rd deck to a line signal...you can pick one up from about £20 off chemical, dunno what the sound quality is like using these tho
On a+h mixers there's a jump switch inside which you can modify to change phono to line and vice versa, there's instructions on their website somewhere I think
On a+h mixers there's a jump switch inside which you can modify to change phono to line and vice versa, there's instructions on their website somewhere I think