Interesting idea, and it should work, I think, with a restriction on the HD400. You don't mention which POD HD you're talking about, but it's either the HD400 or 500 since the 300 has no FX Loop.

I'm not at my HD400 right now (and I don't have a UX2 to test with)  but I have access to the POD HD manuals. Note the following descriptions in the POD HD400 manual:

FX Loop: Pre - Positions the FX Loop before the Amp model (and between FX1 and FX2, if these FX are also set “Pre”).

VOL: Pre - Positions the Volume effect before the Amp model (and before all other “Pre” designated FX) within the signal flow.

So in this case you would not be able to use FX1 in Pre-position, else your signal is no longer dry. And it seems the VOL is positioned before the loop as well - I'm not sure what that might mean.

The POD HD500 has full flexibility with the positioning of the FX Loop (as one of the eight FX blocks) so that should work fine.

I presume you're taking the lead from the FX Send to the UX2 input? I'm not sure whether or not you will have to plug a dummy lead into the FX Return jack to complete the 'circuit'; otherwise the POD HD might ignore the Send since there's no Return.

(Of course, even if this works well enough on the HD500 it's still consuming an FX block and requiring an external audio/DAW interface. I would much prefer the dry record send over usb/ASIO)

EDIT:  Just had an afterthought.........you need to be monitoring the wet signal using the POD HD, but the UX2 is your DAW's audio device while recording the dry signal. Presuming you will also want to monitor backing tracks, you might need to figure out how you will do this. DAWs and audio devices generally have restrictions about multiple connections and routing signals.

according to the PODHD500 manual:

S/PDIF Output (Knob 1): Selects the type of output mode signal fed to the S/PDIF OUT:

- Match Outputs (uses the same output setting as configured on the Page 4 Setup:Outputs screen - see page 2•7)

- or Dry Input (your Source Input signal with no Amp, Cab, Mic, “E.R.” or FX processing applied)."

All of the suggestions above are great and should work for you.

  You CAN record a mono Processed signal and a mono DRY signal via USB with the POD HD500 using record sends 1/2.

  you will need to setup a dual amp preset with the first signal chain having all effects and amp model and the second chain with no effects and amp model disabled.  Make sure to pan the processed signal chain hard left and the second signal chain hard right.

  In this configuration, when using the POD HD500 as your recording interface, Record send 1 is a processed mono signal, and Record send 2 is a dry signal.  Just create a mono track for each, and you sould be able to monitor the processed signal while recording the dry signal.

  Regards,

  Line6Hugo