Pioneer PD9700 analogue stage question

paulrerrie

Member
2008-01-10 10:46 pm
Hi. I was just curious to know, do R577 & C567 (see schematic) form a (12KHz) low pass filter? The stage is described as 'Buffer & de-emphasis' & I wondered if this was intended to actually filter the audio signal rather than decouple digital/RF noise.

Thanks, Paul
 

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Mooly

Administrator
Paid Member
2007-09-15 8:14 am
The whole opamp stage forms what's called a "multiple feedback" filter and is inverting at DC. The opamp is configured as an integrator (C565) and it's performance is hugely opamp dependant. That may be one reason why the stage uses FET's to boost output stage current delivery.