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PCM3008 Audio Sampling

Jamie Brock
Prodigy 10 points
Other Parts Discussed in Thread: PCM3008

Hello All

Im making an audio sampler using a TI   PCM3008 and an STM32 microcontroller.

I am using the recommended circuit from the datasheet but Im not sure if i can send audio straight in or if I need to condition it first.

The datasheet says the Analog Input, Centre Voltage should be 0.5 VCC.

I am using 3.3 as VCC so does this mean I should be level shifting the incoming audio signal to make its centre point 0.5VCC before sending into the PCM3008?

What Im asking really is can I just send audio straight from a 3.5mm standard audio input socket straight into the 'A/D IN Right Channel IN & Left Channel IN' inputs on page 13 of the PCM3008 datasheet.

Maybe I'm overthinking this but I would really appreciate any thoughts anyone may have before I commit to making a pcb.

Many Thanks

  • 0
    Prodigy 10 points

    Yes. Although using an inexpensive Op-amp to isolate the input is a good idea, it isn't necessary. The PCM3008 has an internal reference you can use to bias Op-amps that provides a VCC/2 output. The inputs will need a capacitor of about 0,47uF for DC blocking. Whatever voltage you use for the analog supply will be divided by 2 as the reference voltage. For the outputs you may want to use an Op-amp post filter. The VCOM terminal supplies reference DC. Use a simple active Low Pass filter or an RC filter (you may meed to adjust the gain with an Op-amp after an RC filter, so an active filter is actually simpler). I've had good luck with the PCM3008 before.