Whirlwind pcDI Stereo Line Interface

The output on the pcDI is mic level. There is no need a use a pad.

This is an old question but an answer might help someone else. You shouldn't connect 2 audio sources together on the same side such as LEFT (TS + RCA or 3.5mm) or RIGHT (TS + RCA /3.5mm) because the output impedance of most devices is fairly low. (they affect other devices if connected together) Each device is intended to go into a high impedance audio input like a mixer or DI box where the connected device has little affect on it. (The same reason they make fancy low capacitance cables). If you connect 2 devices to one side that loads it down by connecting a 2nd device across it (which has a low impedance output that partially shorts it out). That drops the output level of your device and potentially neither one works. That would be like the opposite of what we want. That's why they make High-Z input impedance input options on mixers for passive guitar pickups, so that the connected device or mixer doesn't dampen down a small mVolt output. You would probably need an active DI-box or small mixer with small op-amps to present a high impedance load to BOTH devices which is like a small mixer. They DO make 2 and 4 channel active DI-boxes that could do what you want- or a small mixer. Active means it takes power to run it and it's basically has a small amp which makes it easier for your device to transmit without loss of signal. On the other hand - you can connect ONE device to EACH side of the 2 stereo inputs and they won't bother the other side, You'd have mono device 1 and mono device 2 on the 2nd plug next to it. It doesn't connect the 2 sides together unless you click the mono switch on purpose.

No. I use it to go from stereo 1/8 sources (like laptops and cell phones) to one or two XLR's that I then put into a mixer, personally. But you could plug your XLR's into a combo amp or whatever else you want.