If you decide to use dbx units,what I've experienced from recently acquiring dbx units for mine,is that you have to watch what you do on certain gear.
The dbx150X units require that you have a TRS connector on the output-but the Ring isn't connected when going to an unbalanced Otari.The other wire from a 2-wire w/shield cable should go to Shield.The TRS connector is used in the dbx unit so no signal from Pin 2 touches Ground.If there is no wire hooked up to that terminal,then the signal will just sit safely there on that pin,without harming the dbx unit.
If you just used a TS cable,then Pin 2 signal would be touching Ground,because there's no Ring section on a TS cable.
Thanks! I'm not much of a fan of noise reduction and don't plan to use it on this machine. I like a little bit of hiss... it lets me know how loud to turn the music up! I don't mind a bit of consistent hiss in the background, but what I don't like is having the hiss change with the music.
You have to check carefully for each piece of gear, but most transformered balanced outputs should have the minus leg tied to ground, while most electronically balanced outputs of the cheap variety where they just run through an extra inverting op amp should be left floating, as you point out regarding the dbx 150s. I don't think I have any gear with the fancy electronically balanced outputs that sense the output wiring and adjust.