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The datasheet of the audio codec I'm using (CS4272-CZZ) suggest a filter on the differential output pins. Their suggested configuration also combines the signals into a single ended output. I want to amplify this signal using a TPA3116D2, which accepts differential inputs. Using the suggested filter more than triples the component count so I would rather avoid it if I could. So could I theoretically just pass the signal through a capacitor or is the impedence matching an absolute necessesity? If it is, is there a simpler RC filter that can accomplish the same thing?

Thanks!

For reference, this project aims to use speakers as mechanical oscillators. Therefore I'm not specifically designing for sound quality but I do want to maintain signal integrity.

The suggested output buffer/filter

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  • \$\begingroup\$ I’d be cautious; the DAC will introduce high frequency components that could be relatively easily removed by filtering. The class D amplifier may well try to respond to these frequencies and that could cause unpredictable behaviour. \$\endgroup\$
    – Frog
    Commented Aug 25, 2023 at 10:20

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A differential output to a differential input is the ideal way to connect stages - given some caveats ...

  • Level, that one is kind of obvious
  • Filtering - You absolutely must have suitable low pass filtering between the two

A Sigma Delta DAC will have all sorts of high frequency energy in its output. A class D amplifier uses high frequency switching internally to create its outputs. There is every opportunity for these two high frequencies to mix and interfere, to create low frequency artefacts. These will not necessarily be 'golden ears' minor gurgles and whistles, they could be full scale signal integrity 'see it on a scope or a meter' problems. Worse than that, the interference might be very signal or even temperature dependent. You might see nothing in your initial tests, then get blatted when you least expect it. You will need to filter all of the HF from the DAC output before application to the amplifier.

The filter in the 4272 data sheet assumes you want a single-ended output, and a flat frequency response. With your load being 'mechanical oscillators', you may well be happy to accept and correct for a sloping frequency response, and use all passive lowpass filters between DAC and amplifier, especially if the frequency is no required to go over the full audio bandwidth.

Start

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