Adding volume know to a board

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RenegadeSockPuppet

Joined May 28, 2020
1
I am not any kind of engineer. I know you generally put a potentiometer before your amplifier board to add a volume knob to a project. I have this mp3 board that I am making into a white noise box to help someone sleep. It's working great. it just takes 5v usb input power and it's outputting to a 5v 3Ω speaker I salvaged from another project really well. sounds great.. However It had on board buttons for volume, track skip, etc.. it's not just an amplifier sound board. I want to add a volume knob potentiometer but have no idea where to solder that on. I don't prefer anything in line to the speakers as what it would have to handle could change at the board, right? someone bump an on board button or it loses it's stored values and resets to the volume it shipped at and that pot would be wrong or change since the post amp power would change.. or am i worrying too much about that?
 

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MrChips

Joined Oct 2, 2009
21,126
Post more information about the board and maybe we can help you.
Make, model, chip, schematics, web link?
Even a well focused closeup of the board will do.
 

andrewmm

Joined Feb 25, 2011
323
its a voltage divider ,

the player forms the source,
the speaker and a resistor form the divider,

Try as an experiment sticking a few resistors in series with the speaker, see how the volume changes, that will give you an idea of the size pot you could use.

To a first approximation, when the series resistance is the same as the speaker, the sound should have dipped by half.

Just be careful, the pot is going to dissipate power When its at half volume, half is going into the speaker, half into the pot.

Also technically, hearing / sound is none linear.
For instance, a log pot would be used in an audio system, but I think for what your doing, a resistor or two and a switch is going to be perfect.
 
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