This is actually four eggs, all of which work on the Z-5500, and two of which work on the Z-5450.

Z-5500 & Z-5450 Eggs:

1. Second Skin: With the speakers off, press and hold Input, Effect, Settings and Mute all at once, until the screen lights and says "Second Skin On". This will change the colour of the power LED when in stand-by mode, and change the graphics of the volume bars. Do it again to turn it off.

2. Diagnostics Mode: With the speakers off, press and hold Input and Effect until the screen lights and says "Diagnostic Mode On". This will cause the screen to provide stream information when changing sources. Do it again to turn it off.

Z-5500 Only Eggs:

3. Boost Mode: Turn the speakers to maximum volume, then continue to turn the knob. Eventually "Boost 1" will appear, and if you continue to turn the knob it will ascend to "Boost 11", a perhaps over-done Spinal Tap reference.

4. Volume+ Mode: While adjusting the volume, press and hold the Mute button and turn the knob right. It will add "Volume+1".."+11" to your volume level.

Also, try this in "Boost" mode, and it will go up to Boost 22. You must hold the Mute button again while turning it down to clear the increase.