It was a more powerful version of the psychic beacon. The beacon activated in Washington D.C. was effective over a metropolitan area, while an active psychic amplifier in Chicago would affect much of North America.
The construction of the Chicago psychic amplifier initially went undetected. Allied forces were drawn to the city in response to what was regarded as yet another Soviet offensive. When the amplifier was detected, it quickly became the focus of the Allied counter-attack and was destroyed before being activated. The destruction of the amplifier prompted General Vladimir to activate a hidden nuclear warhead in Chicago, completely destroying the city and all Allied/Soviet forces in it.
Yuri did not use it during the Psychic Dominator Disaster. As the amplifier is essentially a significantly enhanced psychic beacon, it shares the flaw that, should the structure become damaged beyond repair, the device deactivates. The newer psychic dominator was designed as a perfection of its design (and Yuri's hidden trump card).
The psychic amplifier is 3x3 tile building that serves no other purpose than being a destructible objective, as its functionality is tied to triggers.
A psychic amplifier, along with two psychic beacons, are seen in the Yuri's Revenge skirmish map City Under Siege, merely being used as props.