I use the following procedure for setting mine up.
- Insert the Effects unit into the send/return channels.
- Roughly set the levels, inlcuding WET/DRY on the Effects
- Put some music on
- On the DJR400 open the return level to full
- On the DJR400 open the send level on one channel to full
- Now start adjusting the effects units various levels until you get the desired level and maybe go a little too loud
- Adjust the return of DJR400 to reduce the level, in case you need some gain later
- Now you just use the sends and leave the effects unit alone apart from adjusting the actual effects
- Enjoy the music and add some spice with the send's on the DJR400.