[sci.electronics] Multiplex filter

rambler@pnet51.orb.mn.org (Dan Meyer) (06/16/91)

strong@ee.rochester.edu (John Strong) writes:
>How about simply turning the filter off when making CD recordings?
>There should be a switch that allows you to do this. The multiplex
>filter is supposed to attenuate noise from FM signals that are
>being decoded (for stereo separation). If there is no switch to do
>this you will need a schematic of the unit to eliminate this area
>from the signal path.
>
>John Strong

BZZZT! Wrong.

The Multiplex filteris simply a lo pass filter with a cutoff of about 15 kHz.

what is does is wipe out any multiplex pilot tone that may have gotten through
your reciever. as you know, the pilot tone is 19 kHz, and any leakage of this
tone might fool the noise reduction circut into thinking that there is
significant high frequency content, when there is not.

the swith should make no audible difference when recording from fm radio,
since fm radio is already limited to a 15 khz frequency response. 

also, only the golden eared among us will notice any difference recording from
CD (or any other source with a better frequency response than fm).


no need for flames. 


-- Dan

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