Hello Guys,
Back on line. Firstly , thanks for taking the time to reply; I appreciate it.
So, based on the comments above and finally pulling my head out of it and thinking about it: I have taken the Audiobox iTwo out of the loop and connected up the Helix as the sole USB audio device. So I now have the following chain:
PC -> Helix -> Yamaha (Line) -> Art-415
The result is that I have a nice sound for Youtube, iTunes and my backing tracks - really strong and clear. However, when I play the guitar through this set up via the Helix guitar input I have a low volume and it is fizzy. I have checked that the Global EQ is off and I have checked the out settings are Line for the XLR.
As a next step I will do a new Factory reset and then record through one of the standard presets. Just to be clear at this stage I am not trying to tune the sound to a particular artist or anything, I just think that I should be able to take one of the presets and play it such that I can recognise that the signal is clean and that to some extent it is representing what it is supposed to be; albeit that it needs to be tweaked for my guitar etc, to get an exact sound.
Beyond that I will take one of the Helix Channel or Glen Delaune Presets and record that - and then play it back. Here the difference should only be my guitar, I am comparing a digital media recorded direct from a Helix via USB to a Helix recorded direct from USB with the same settings and both rendered over the same DACs, speakers etc. - they should be comparable.
I will post these recordings when I have finished. If this is not right then I will need to look for an idiocy on my part (always likely), or assume I have a defective unit.
Again, thanks for the help,
Chris