hidden , bu where?

This is from the TiKan Audi HU site and is usually pretty accurate:
1.Turn off radio.
2.While pressing and holding the Preset 5 button, turn on radio.
3.You'll see a series of 8 digits displayed. From the factory, it's set to "55555555". You will not hear any sound when running in this mode.
4.The first four digits correspond to the four equalizer bands (low, low-mid, upper-mid, high) for the front speakers, and the last four digits are the same for the rear speakers. The level can be set from 1 (minimum) to 9 (maximum).
5.Turn the volume control knob to increase or decrease the level for the band (which is blinking). To advance to the next band, press the P.Scan button.
6.When you are done, turn off radio, then turn it back on to hear the results. On some versions of the Symphony, you must also cycle the ignition key to hear the results.