There are bad, better and best ways to convert a stereo device output into an input suitable for connection to an mono audio input such as on a 1502AI or Titan frame input.  This article covers the best way.

The attached graphic shows the schematic diagram that uses three resistors in a summing network.  The suggested values on these resistors are 4.7K for R1 and R2 and 47K Ohms for R3, although the exact value is not as critical as the 1:10 ratio.  So for example, if one has 1 K and 10K resistors, that will likely work as well. 

When connecting to a balanced mono input, one may not connect the ground on the mono side if there is a chance of creating ground loops.  It is only required to connect to the + and - terminals.