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PCM2901: Always detected as Microphone and Noise under several circumstances

Reinhard Bergmann
Prodigy 10 points
Part Number: PCM2901
Other Parts Discussed in Thread: PCM2903C

Hi to all,

we use the PCM2901 in an application as some kind of USB Sound device. The first problem:

in all OS (we use WIN7 and WIN10) the PCM2901 is recognized as a microphone. Question, how can we turn it to a line-in interface?

Under WIN7 the "microphone" input produces noise.

Test set-up:

Analogue input is shorted to GND to avoid external influence. Than we do a recording from the "microphone" input with Audacity (2.12). A clear audible noise is present.

Also installing of the Driver Filter from TI (slac156 64bit) change not the behaviour. We see that effect with

Under the latest version of WIN10 the "microphone" input produces no noise.

The same device as used under WIN7 is working as expected (except it act as a microphone). The same set up generates no noise.

Under an older version of WIN10 the "microphone" input produces noise

Under an older version of WIN10 we see the same behaviour as under WIN7. The difference is, when we install here the Driver Filter from TI (slac156 64bit) the problem is solved and no noise is present.

Question: what is the difference between this three cases and how we can stop the noise for WIN7, too.

  • 0
    TI__Guru 57800 points

    Hi, Reinhard,

    Welcome to E2E, Thanks for your interest in our products!.

    The PCM2901 has some known issues that are described in the SLAZ036A Errata report. These issues were fixed in subsequent revisions of the PCM29xx family of devices, but unfortunately, the PCM2901 was not revised. I would recommend to try with a PCM2903C instead of a PCM2901, these devices are pin to pin compatible and share similar characteristics. About your question, the device is detected by the OS as an USB audio Codec that features a microphone input for recording applications. 

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer