[TenTec] Digital noise in Omni 6+ audio

[Dave Edwards]

Actually, I've never noticed it in my 6+.
Not that it isn't there...just never heard it.
....Dave


On 4/5/15 10:12 AM, Barry N1EU wrote:
> 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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