0

Amp100 and external mute options

Christoph Krämer

March 26, 2023 14:39

None

Follow

• Facebook
• Twitter
• LinkedIn

2 comments

• 0
  
  Christoph Krämer March 26, 2023 14:51

  Hi all

  1st: sorry for the initial empty post, I hit enter all too soon :-)

  I am about to add an amp100 based subwoofer to my beocreate 4 (bc4) based speakers. In order to keep the females in our hosehold cool, I'd like to avoid the famous infamous pos at powerup. For the bc4's I added a dsp project file and a timer relais. Works like a charm - for all bc4 based stuff.

  On to the amp100: I read the docs, namely in "https://www.hifiberry.com/docs/hardware/gpio-usage-of-hifiberry-boards/", section on amp100:

  HiFiBerry Amp100
  ...
  GPIO4 is used to control the MUTE function of the power stage. Pulling it to high will mute the output

  "GPIO4": Raspis GPIO4 or what else?

  Further: "Pulling it to high...":

  1. What level? 3.3V, 5V or VIN?
  2. I guess there should be a pullup resistor to keep currents low, correct?
  3. What value?
  4. If muting occurs on "high" level, what happens at power up:
     popping noise will occur?
  5. On the bc4 I hat to simple add a normally close timer to the mute jumper. That looked to me to an easy, well pre-thought solution. Is this really the same on the amp100?

   

  Greez

  chris

  Edited by Christoph Krämer March 26, 2023 14:54
• 0
  
  HiFiBerry team March 27, 2023 09:37

  This pinwas never designed to be used fromoutside. Yes, it's GPIO4 from the Pi and you have to pull it to 3.3V. Otherwise you will damage your Pi. 
  I would use something like 50-100kOhm.
  
  The state of the Pi's GPIOs on boot depends on all kinds of configurations. Usually GPIOs are configured as an input which makes the state undefined.