There's a fair amount of low-level objectionable noises (high-pitched
tones, tuning encoder noise, etc) in the Omni 6+ receive audio. It
detracts from what is otherwise a fantastic sounding receiver. Using the
LP function gives some, but not complete, relief to the high-pitched tones.
Has anybody investigated/analyzed this to any degree? I would think that
the noise must be introduced where the IF/AF board audio loops to the CODEC
(via cables 54/56) on the logic board for dsp processing. I pulled the
logic board and was surprised to find that the CODEC chip's "analog" ground
U11-17/18 is isolated from the rest of the logic board and is only
connected to the shield of cables 54/56. Yet the shield of cables 54/56 IS
connected to chassis ground back on the IF/AF board. This just leaves me
scratching my head - has anybody else looked at this circuit or can
otherwise comment on this grounding scheme?
I also looked at the +5V supply to the CODEC chip U11 and no glaring issues
jumped out at me.
73, Barry N1EU
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