Question: 

I want to use the BluBOX only with the AMP1 without a guitar cabinet. How should I connect it to get the best sound?

Answer:

You'll get the best sound by connecting the speaker output of the AMP1 (8ohm or 16ohm / it doesn't matter) directly to the SPEAKER LEVEL IN of the BluBOX. If you don't have a guitar cabinet connected, a standard instrument cable or patch cable will suffice. However, if you plan to route the signal at any point, both cables (from AMP1 to BluBOX and from the BluBOX to the guitar cabinet) should be speaker cables.