At most of my employer's locations we use RDL D-J2 (D-J2 ‐ Line Input Assembly) or similar wall-mounted inputs for laptop playback through an installed system. According to the manufacturer, the device does the following: "LEFT and RIGHT are combined and balanced through audio transformers configured to reject induced hum." The cable coming out the back of the plate is just a 3-conductor wire.
According to the copy, the summing process inside the device is supposed to combine and balance L & R down to a mono line. In practice this works fine for music produced in the last decade, but anything from the 70s with hard panning (Bohemian Rhapsody, Pinball Wizard) results in almost complete loss of the L signal. I confirmed this by listening to the track with headphones and taking the left cup off of my ear. What I heard through only the right cup was what our system was reproducing.
Is this device just doing a bad job of summing to mono?
According to the copy, the summing process inside the device is supposed to combine and balance L & R down to a mono line. In practice this works fine for music produced in the last decade, but anything from the 70s with hard panning (Bohemian Rhapsody, Pinball Wizard) results in almost complete loss of the L signal. I confirmed this by listening to the track with headphones and taking the left cup off of my ear. What I heard through only the right cup was what our system was reproducing.
Is this device just doing a bad job of summing to mono?
