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I recently got a cheap Bluetooth speaker. It works fine, but the indicator melodies (the beeps it makes when it turns on and off) are positively deafening. I'm slowly learning about electronics, so my first naive thought was: those "melodies" are stored on the device, so their signal travels a different path to the speaker than whatever I send to the speaker via Bluetooth. If I can identify that path, I could add a resistor there to muffle the sound.

Looking through other questions, I gather that adding a resistor could work, but is a bad idea in many cases. My hope is that I'm in this situation, rather than this one.

After staring at the circuit board for a while, I learned that I don't know enough. I can identify some parts, but not others. The Bluetooth antenna leads to a chip, and I think I found the datasheet here (http only).

the speaker's circuit board

The point where I'm stuck is this: Are there components that can be identified as being the amplifier or the memory, or would those be integrated into the chip?

My main goal here is learning, with possible side effect of making the speaker more pleasant to use, so I'm grateful for anyone who can provide some more info. I assume the most practical solution will always be to buy a better speaker, but that's not as much fun, is it?

Edit (gathering info from the comments):

  • the component marked M1 is a microphone
  • the amplifier is a HAA8002D, and can be muted
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  • \$\begingroup\$ What is component M1. I know that designation as a motor and I can't imagine a motor in a shower speaker. Any possibility that is an annunciation of some kind? Just a shot in the dark. \$\endgroup\$
    – DrG
    Commented Dec 23, 2022 at 17:18
  • \$\begingroup\$ The overly loud tones could be a simple matter of "gain staging". Turn on the BT speaker and use its volume- button to lower the volume until the connection messages are tolerable. Then increase the media volume on your source device (phone, tablet, etc), and not on the BT speaker. \$\endgroup\$
    – Mark Leavitt
    Commented Dec 23, 2022 at 17:34
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    \$\begingroup\$ M1 is probably a microphone. And will provide hideous voice quality if you’re foolish enough to make calls from the shower. \$\endgroup\$
    – Mark Leavitt
    Commented Dec 23, 2022 at 17:52
  • \$\begingroup\$ Can you post a schematic? \$\endgroup\$
    – Gil
    Commented Dec 23, 2022 at 19:14
  • \$\begingroup\$ @DrG I can confirm M1 is a microphone. \$\endgroup\$
    – hgjd
    Commented Dec 29, 2022 at 18:17

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You are pretty much out of luck.

There are only two ICs showing on the PCB:

enter image description here

U2 (circled in red) is an audio amplifier. It doesn't have any kind of sound generator in it.

The larger IC circled in blue is the Bluetooth IC. It does everything else. It reads the buttons, does the Bluetooth transmit and receive stuff, and generates the sounds. YThere's no place to "grab" the power on/off sounds that won't also "grab" the regular audio.

You might be able to do something if the LEDs come on after the power on signal. You could use the LED signal to mute the speaker until the LED comes on. Something similar might also work at power off. You'd have to observe the LED sequence and the power on/off tones to see if it might work.

The amplifier might even have an "enable" input that you could control from the LED signals. I can't read the part number on, though, so I can't check its datasheet to see.

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  • \$\begingroup\$ I've identified the amplifier IC (HAA8002D, for anyone interested), and found that I can disable it from pin 1, so with some precision soldering I could mute the sound while the power button is pushed. Thanks! \$\endgroup\$
    – hgjd
    Commented Dec 29, 2022 at 18:10

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