A catheter shaft design facilitates allows for simultaneous stringing of wires and maintains a desired spacing and separation of the wires. In one implementation, a catheter shaft (504) and a core structure (500) are formed in separate manufacturing sequences. The core structure (500) includes a number of receptacles (506) formed in an external surface thereof and may further include a central lumen (508). Wires (501a,b, and 502a,b) are placed into the receptacles (506) and the core structure (500) with wires (501a,b and 502a,b) are inserted into the lumen of the catheter shaft (504). The wires (501a,b, and 502a,b,) can then be connected to electrodes or attached to a catheter tip so as to permit steering of the tip. The design can serve as a platform for various types of catheter.