A carriage for a disc device, which has a top arm, bottom arm, and mid arm, has a main mode, end arm mode, and mid arm mode as a frequency response obtained when subjected to a vertical shake. It is proposed that the stability of the controller first be established or excluded, that the control characteristic of the controller be altered and that the stability be checked again, and that those steps be repeated in a loop. The synthesizer includes a direct path loop filter which is coupled to a charge pump output. The compression section of the line selectively biases against a portion of the line extending out of the working passageway so as to selectively lock the line to the body when the line is tensioned against the body. A digital signal processor interface to the drive electronics of the CD drive, a dynamic random access memory controller, an error correction code data corrector, an error detection and correction device employing cyclical redundancy checking techniques, and a host computer interface are described.