any body know what synth has that old school rave sound.Its in charlie from prodigy and alot of hard house producers use it just wondering if anyone knew what synth it is???

You probably mean the sound "Rave"

For instance the Yamaha CS2x has it !
This is a great synth for making Dance, Techno and Trance music !!

In Performance mode the sound is called "Raveline", and in Multi Mode it is called "Rave".

Besides this, it has alot of other great sounds !!

If you're talking about the "hoover" type sound its done on Alpha Junos