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  1. #1
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    PCP + Khadas Tone Board - DAC controlled volume?

    Hi. I started a discussion on the thread ANNOUNCE: piCorePlayer 5.0.0 (starts on page #518) and it was suggested to start a new thread (thanks to @Man in a Van and @paul- for their help so far). To summarize…

    As I understand it, the ESS9038Q2M DAC chip (as found on the Khadas board) can control the volume of its outputs (instructed by i2c). I understand that this is potentially an optimal method of controlling volume is because it does it by using some serious “hardware” oversampling (or something like that) which is preferable to altering the stream in software before it is sent to the DAC (where it is usually advised to leave volume setting in players at 100% for bit-perfect transmission). Of course, chip-level volume control also offers us the opportunity us to remove pots / stepped attenuators from the signal path (if we dare to place trust in our settings!)

    Now, I am certainly able to control volume coming out of the Khadas board (which attached to a Pi 3B via USB) using the slider on the LMS interface – but I would like to understand what PCP is doing. Is PCP:

    A - doing software adjustment of the stream sent to the DAC (i.e. not bit perfect)

    … or…

    B - sending the original bit perfect stream and instructing the DAC (via the driver) to alter its outputs (i.e. the supposedly preferable method).

    If it is not doing B, can it be done? I would be very grateful for any advice.


    Some relevant info…


    Many thanks for listening!

  2. #2
    Senior Member paul-'s Avatar
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    It sure does appear that you need that specific firmware loaded. If you do, on pCP goto the Diagnostics page, then select the Sound Page.

    Look for the amixer section.....what is the contents?
    piCorePlayer a small player for the Raspberry Pi in RAM.
    Homepage: https://www.picoreplayer.org

    Please donate if you like the piCorePlayer

  3. #3
    Junior Member
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    Quote Originally Posted by paul- View Post
    It sure does appear that you need that specific firmware loaded. If you do, on pCP goto the Diagnostics page, then select the Sound Page.

    Look for the amixer section.....what is the contents?

    Here are the two sections with amixer in the heading:

    [ INFO ] amixer cset numid=3
    numid=3,iface=MIXER,name='Khadas Tone Control Playback Switch',index=1
    ; type=BOOLEAN,access=rw------,values=1
    : values=on

    [ INFO ] amixer
    Simple mixer control 'Khadas Tone Control ',0
    Capabilities: pvolume pswitch
    Playback channels: Front Left - Front Right
    Limits: Playback 0 - 127
    Mono:
    Front Left: Playback 127 [100%] [0.00dB] [on]
    Front Right: Playback 127 [100%] [0.00dB] [on]
    Simple mixer control 'Khadas Tone Control ',1
    Capabilities: pvolume pvolume-joined pswitch pswitch-joined
    Playback channels: Mono
    Limits: Playback 0 - 127
    Mono: Playback 127 [100%] [0.00dB] [on]

  4. #4
    Anyone got this working yet?



    Sent from my ONEPLUS A3003 using Tapatalk

  5. #5
    Junior Member
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    Quote Originally Posted by bennyboyph View Post
    Anyone got this working yet?



    Sent from my ONEPLUS A3003 using Tapatalk

    Doesn't seem so. Think I'll try my luck on the Khadas forum.

  6. #6
    Senior Member paul-'s Avatar
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    It’s really not clear

    1). Is there a hardware mod or add on board required?
    2). If it is just firmware, then where is the source code for the program to control it?

    Or is it just done through an Alsa mixer after the right firmware is loaded?
    piCorePlayer a small player for the Raspberry Pi in RAM.
    Homepage: https://www.picoreplayer.org

    Please donate if you like the piCorePlayer

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