Did it come with documentation? If not...here's the snippet taking from the documentation that I easily accessed on the Groove Tubes website.

Instrument DI:
Insert your instrument into the far left 1/4” input
labeled “INST INPUT”. There is zero gain added
(ie: Unity Gain”) when the Gain control is fully
counterclockwise.
You may pass your instrument signal onto another
stage amp by using the “INST THRU” 1/4” output jack
located directly to the right of the “INST INPUT” jack.
This will not affect the Brick’s preamplification gain or
tone.

What this means is that if you were sending an instrument signal into the Brick, you could split that via the INST THRU and send that to another device such as an amplifier.

You should NOT use the INST THRU to go do your DAW. You should use the standard output on the Brick for that. The INST THRU does "bypass the tubes" but not to make the sound any cleaner. It's really just a signal splitter. The sound that comes out of the INST THRU should be exactly the same sound that is input in the INST INPUT.

Just go [[url=http://[/URL]="http://www.groovetu…"]here[/]="http://www.groovetu…"]here[/].

Thanks

Ahh I got it now thanks.