Inputs 1-8 are all balanced TRS jacks.Inputs 1-2 on the front have the front mounted gain knobs and -26dB pads. These jacks can support +18 dBu input signal with the pad in and the gain knob set fully counter-clockwise. The specs we publish in the manual and on our datasheet/website were confirmed using inputs 1-2. The Neutrik connector can support balanced/unbalanced TRS inputs and balanced/unbalanced XLR connectors. (I'm not sure why you'd ever want unbalanced XLR connectors, but that's the way it is wired).Inputs 3-8 on the back are also balanced and have software controlled gain. The inputs are optimized for +4 dBu or -10 dBV line levels (all other gain settings offer specs close to our published specs, but we can only guarantee our published specs at the +4 and -10 settings). If you go into the Other Options dialog, you will have 8 choices for input gain attenuation or sensitivity. The box defaults for the -8 dBV line level. The reason we didn't default the box for -10 dBV was due to some newer synths that run slightly hotter than -10 dBV (hence -8 dBV instrument level). If you sent a full code signal into input 3-8 with the input gain set for -10 dBV you might clip the input(s). On the flip side, if you have a low-level output from your synth, you may not be getting enough signal into the 001. In that case, you should increase the input gain to -10 dBV first and see if that works. If not, go back into the Other Options dialog and increase the gain below -10 dBV (there are two more settings below -10 dBV. If you are using +4dBu line levels, then you should open the Other Options dialog and lower the input gain all the way (this is marked with the +4 dBu line-level label). Use an Aux track in Pro Tools to check your levels. With the fader at nominal (option-click the fader) the input should be metering in the yellow area for a good clean signal. Inputs 3-8 can support a maximum input level of +18 dBu (in the +4 dBu line-level gain setting). The inputs support both balanced and unbalanced connections. On the outputs, only the monitoring outputs and the main outs 1-2 are balanced. This is strictly due to power consumption. Since we are drawing power from the computer, running all outputs with balanced line-levels at full code would require more than 2X the power we are currently drawing from the computer using unbalanced connections. The computer does not supply enough power through its PCI ports to power 8 balanced outputs at full code as well as phantom power, and a headphone amp (which can output up to +17 dBV @ 600 Ohm loads, +14dBV @ 150 Ohm loads).