ABSTRACT
The switching and routing of analogue signals is a fundamental part of signal processing, but not one that is easily implemented if accuracy and precision are required. This chapter focuses on audio applications, but the basic parameters such as isolation and linearity are equally relevant in many fields. A mechanical switch normally makes a solid unequivocal connection when it is closed, and it is as ‘on’ as the resistance of its contacts and connections allows. Using an ALPS SPUN type push switch, at 10 kHz the offness is only -66 dB, and grounding the unused side of the switch only improves the offness by about 2 dB. Some time ago, Morgan Jones raised the excellent point of crosstalk in the input-select switching of preamplifiers. Any electronic switching technique must face comparison with relays, which are still very much with us. It is possible to cascade FET switches which is taken from a real mixing console application.
