Hi,
 
I am trying to fix ground loop using DI box but I get substantially lower output level from a passive DI than from the active one. No attenuation is selected.
 
I run Focusrite Scarlett 8i6 from my PC to Yamaha monitors and have active DI box Palmer PAN 02 and passive ART dPDB (dual DI box).
 
Usually, the gain knob on Yamaha monitors is set in the first quarter in order to get decent loudness levels. However on the same gain level, the signal through passive DI box is less louder than without or with the active DI box.  Why? Is it normal?
 
Thank you for your help.
 
 

Yes, this is normal.  My favorite passive direct box of all times is the Radial JDI.  It uses a Jenson transformer which is one of the highest-quality audio transformers made, and the box costs more than a lot of active direct boxes.  It has a lower output level than almost every active direct box I've ever used.  Active direct boxes need power to run and as part of their design, they are able to apply some amplification to the signal.  This is also why dynamic and ribbon mics (which are passive) tend to have lower output levels than mics that use active circuitry.