Digital Audio Concepts has released the "SID Symphony II" cartridge. With this cartridge you can add a second SID to your Commodore C64 without opening the C64. Features: SID register mapping from $DE00 to $DFE0. Access LED. Reset button. 12 V DC-to-DC converter for 6581 SID chip. The price of the SID Symphony II cartridge, without an SID chip, is $39.95.