analog switches and thd

Martin Czech martin.czech at itt-sc.de
Wed Jun 25 13:06:37 CEST 1997


I want to avoide a lot of relays in an multiple input switching
matrix for an 8-channel audio system with 2x8-track, 2x-track, 2xCD and 2xDAT
interface with independent level and EQ control for up to eight spatial distributed
loadspeakers (is this called octophony ?).

It's a DIY birthday present for a friend.

Up to now, he has to run arround to regulate the sound at EVERY
active loadspeaker (Yamaha), and there's always some awful
switching noise during the performance, since he has no fade out
box.

Real studio quality is not required concerning THD, since the loadspeakers
will allready contribute some distortion, it's for live performances.
But too much noise would be awfull.

Does anybody know, how much distortion (thd) is introduced
by using a cheap CD4066 CMOS-Switch instead of an expensive relay
@ Vdd=7.5V, Vss=-7.5V, Vsignal 1Vpp, signal current 100uA ?

And what about noise ?

Crosstalk will be no issue, I could use different ICs in such a case.

Any experience out there ?

m.c.




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