The ornamental design for a connectablesignalprocessingdevice, as shown and described.
FIG. 1 is a perspective view of the front, top and right side of a connectable signal processing device showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom view thereof.
The broken line showing of the connectable signal processing device is included for the purpose of illustrating unclaimed portions of the connectable signal processing device and forms no part of the claimed design.