• State Resolved
  • Locked Locked
  • Replies 12 replies
  • Subscribers 32 subscribers
  • Views 1974 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

PCM2704C / PCM2705C Volume Control

Norbert Richardson
Prodigy 40 points
Other Parts Discussed in Thread: PCM2705C, PCM2704C, DIR9001, PCM2704

We are planning to use one of the parts listed above (PCM2704C / PCM2705C) in a desktop speaker with a USB input. Please confirm if these parts will allow an end user to control the volume of their desktop speakers from their computer (PC or MAC) while keeping the audio signal in the digital domain.

  • 0
    TI__Guru**** 189399 points

    Hi, Norbert,

    Welcome to e2e, and thank you for your interest in our products!

    Absolutely! The part will work as you want.

    -d2

  • 0 in reply to Don Dapkus
    Prodigy 40 points

    Hi Don,

    We have purchased the evaluation module. We have found that by default it has adjustable volume when you use the analog output and a fixed volume when using the SPDIF output. Please provide details on how to configure the part so that it will have adjustable volume when using the SPDIF output. Statements in the datasheet indicate that the 2704 and 2705 should allow for level control of the SPDIF output. How do we enable the level control?

     

    Thanks,

    Norbert

     

     

     

  • 0 in reply to Norbert Richardson
    Expert 1720 points

    Hi Norbert,

    On PCM270x it is not possible to control volume of digital output (S/PDIF, I2S), but on Windows7 it works. It is possible, that Win7 modify audio stream on software level and send them to the USB soundcard already modified.

  • 0 in reply to Pavel Ruzicka
    Prodigy 40 points

    Hi Pavel,

    Please provide instructions on how to enable this function with Windows 7. We were using Windows 7 with the evaluation kit.

    Please let me know if TI has another device that has the functionality for Windows and Mac OS.

    I appreciate your assistance but it is frustrating that the previous response told me that it would absolutely work and someone from the TI technical support told me it would work. TI needs to make sure that the correct information is being communicated.

    Thanks,

    Norbert

  • 0 in reply to Norbert Richardson
    TI__Genius 11110 points

    Hi Norbert,

    I have verified that on Win7, using the OS volume control can not change the S/PDIF output volume, but can change the music player software's volume to do this.(e.g. windows media player, foobar2000 etc.). Below is the test I using foobar2000, you can see the S/PDIF volume has been changed.(S/PDIF output fed into DIR9001, converts to I2S to AP)

    -Jacky

  • 0 in reply to Jacky Wang(QD)
    Prodigy 40 points

    Hi Jacky,

    Thank you for your response. Does TI have a USB audio device that will allow the end user to adjust the volume while using a digital output?

    Thanks,

    Norbert

  • 0 in reply to Norbert Richardson
    Expert 1720 points

    Hi Norbert,

    your first question was probably not perfectly clear. It can be reason, why Don write you, that it is possible. Usually it is not a good idea to reduce volume by digital way, because you loose bit resolution on lower volume. It is better to set volume on analog part or some 32bit DACs have possibility to set volume on the digital part without loose of bits.

    Pavel

  • 0 in reply to Norbert Richardson
    TI__Genius 11110 points

    Hi Norbert,

    If you want, you can use TAS1020B or TUSB3200, which parts have USB to I2S converter function.

    Thanks.

  • 0 in reply to Jacky Wang(QD)
    Prodigy 100 points

    Hi Jacky and TI Engineer.

    Volume of the application(foobar2000) was indeed variable.
    Also,
    PCM2704 ANALOG OUT:
    Master volume on the PC is valid.

    However,
    PCM2704 SPDIF OUT:
    Master volume on the PC is invalid.

    Would you teach the mechanism in which SPDIF OUT is fixed? 

    And,This specification is confusing for a user.

    I have a request to PCM2704.
    PCM2704 SPDIF OUT should prepare OPTION interlocked with PC Master Volume.

    Regards

  • 0 in reply to masaki matsuoka1
    TI__Genius 11110 points

    Hi Masaki,

    It has been stated clearly in the datasheet, the digital volume control does not affect the S/PDIF.

    Thanks!

  • 0 in reply to Jacky Wang(QD)
    TI__Expert 5555 points

    Hello folks,

    Quick Introduction - I'm the systems engineer who adopted these parts! They are getting a little old now, with little possibility for any silicon changes at this point.

    I too asked about the S/PDIF output control a number of years ago with regards to these parts.

    It was pointed out to me that it's expected that the following DAC and Amplifier for S/PDIF out is responsible for volume control. Similar to what previous posters have said. However, I think it makes a lot more sense if you start to worry about compressed audio data as well. As soon as you touch a compressed audio datastream, you corrupt the data. In fact, many other systems such as TV's and DVD players with S/PDIF out, don't modify their S/PDIF outputs either. I would need to go digging through S/PDIF specifications to see if there's any mention of volume control pre-transmit.

    From what I've read here, the datasheet is rather clear on the impact of the standard windows mixer on the PCM29xx S/PDIF output. I understand that is a frustration (it was for me when I spotted this functionality too!), however, at this time, there is little we can do to change the functionality.

    Thank you again for evaluating TI silicon. Rest assured that as we begin to investigate USB devices in the future, I'll add pre-transmit-volume-controls as part of the feature set! :)

    Thanks again

    Dafydd Roche

  • 0 in reply to Dafydd Roche
    Expert 1720 points

    Hi Dafydd,

    I agree that modifying of S/PDIF signal is corruption of signal specially in HiFi. It is better to change volume in analog part behind DAC or in a DAC with more bits. It is a good idea to have option for this function if somebody want it. For me MUTE is enough.

    Are there any plans to create a new USB CODEC and DAC with support for 192kHz/24bits (or 32bits)? I2S output and asynchronous transfer is also wanted. Today it is not easy to create USB soundcard with these parameters.