HD500X FX Loop issues with amp

[martinigd]

Hello

 

I've purchased HD500X recently to use with my amp via 4 cable method.

 

I have the following problem:

Whenever I engage FX Loop via my amp's footswitch or by activating FX Loop on my HD two things happen:

- volume drops

- my amp goes from Dual Rectifier to poorly setup Line 6 Spider tone-wise (1000% more digitally sounding with strange flange/phasing ontop)

When I disengage FX loop, everything goes back to normal

 

I got rid of volume drop issue by increasing FX Loop Return by 12dB but it seems to be a lot and it worries me, plus there is no way to get rid of this digitalish mess.

 

What I've already double checked:

- All connections (everything is connected fine)

- All HD500x Settings (I set it up according to other what other success 4cm posts on the web and this forum say)

- I tried to fiddle with all possible settings, nothing changes 

- I don't use any amp or cab modelling (disabled), just pure fx loop / mixer at this stage

- All other effects are off (chain is empty apart from mentioned above)

- I've dummy-patched my amps FX Loop and everything is fine without HD500X so it's not the amp.

 

Please help me out, I'm on the edge of throwing this out of the window and I'm starting to lose hope that I'll ever be able to set it at at least acceptable level...