To reset a SoundTouch SA-4 amplifier:
Unplug the amplifier's power cord for 1 minute, then reconnect it
On the back of the SoundTouch wireless adapter, press and hold the Control button for 15 seconds
After 15 – 30 seconds, the wireless adapter should turn on and reconnect with your network. The connection is complete when the indicator on the back of the adapter is solid white.