The company believes the defective kits stem from an "isolated manufacturing issue" that occurred early on, with those affected urged to contact customer support.

Activision also noted that it will soon offer players a "drum tuning kit" to ensure drums are properly optimized, and said it will perform more random quality tests.

Guitar Hero World Tour arrived on PS2, PS3, Xbox 360 and Wii this past Sunday, with reports soon coming in of defective drums and guitars. Today's statement only applies to the drum kit issues--the company has not offered a statement on the guitar woes some report--with the controllers covered under warranty.

Activision's full statement follows:

We have learned that certain drum kit controllers manufactured for Guitar Hero World Tour have sensitivity issues. We believe that these controllers are limited to ones in the earlier manufacturing stages. While we believe that this was an isolated manufacturing issue, we are stepping our efforts to randomly test our drum kit controllers so customers can be assured they work properly. In the event any consumers do experience problems with their drum kit controllers associated with sensitivity issues, Activision will soon be offering a drum tuning kit that will enable players to fully optimize their drums.

Our goal would be to immediately address any hardware issues Guitar Hero World Tour players have with the game. Consumers should visit the Activision Publishing customer support website at www.activision.com/support website or call 310 255-2050 in the U.S. where a customer care representative will assist them. Activision is fully committed to the highest quality manufacturing standards, and to satisfying every Guitar Hero World Tour fan so they can enjoy the best musical gaming experience ever created.