I am a highschooler who has taken interest in electronics and circuits. I have been working on a small Bluetooth speaker for quite some time now. With the little knowledge I have, I scrapped together a working (if I dare say) circuit, however I am redesigning based on how the first prototype went. It was very scratchy and distorted and had a poor maximum volume. The goal with the redesign is to (A) put all components on a PCB board in attempt to decrease resistance and clear up the scratchiness and distortion and (B) properly distribute wattage through the design to make it louder. While trying to draw a schematic for the redesign I realized I don't know proper procedure on how to get the power from the battery to the two amplifiers and computer chips. I attached the schematic to the redesign as well as a little video of my first design here. I would also really like having the modern charging architecture where the device can be used while charging.

I am specifically wondering:

1. How do I figure out what specific parts I need? From my understanding, I will need something to boost the voltage before sending it to the amplifiers as well as something to regulate/boost voltage into the I2S receiver and DAC.

2. Can one boost converter (or whatever would be best fit to increase the voltage) be used for both amplifiers, or do I need one for each? If one can power both, then do I set it to double what is required by the boards in order to supply them both with max power? To me this seems like it would risk sending too much power to one of the boards and might destroy it.

Also, if anybody has advice on designing the PCB or critiques on my current design it would be immensely appreciated.

- The battery is a single 3.7V 2600 mAh Li-ion cell link


- I2S Receiver and Master Clock link


- Amplifiers (2) MAX98357A 2.5-5.5V 4-8hm 3W link


- Speakers 2-3W 8Ohm 200Hz-20kHz link

- I still need to design/pick out parts for a PMIC (I don't really know
what I'm doing here)

- Still need to pick pick out a DAC

I haven't purchased any of the new parts, so I am open to changing parts for the sake of a better design although I do have speakers and amplifiers left over.

Thanks,

Oliver

 

your schematics has much to desire:


integrating random pieces of hardware requires strategy. your sketch does not even include the I2S receiver.
omitting things for clarity can be justified but your sketch is lacking a lot of things which does not help with clarity.
you can for now skip optional items (battery, PMIC, use charger) and simply use PSU to get things started. then focus on functionality.
you have I2S moules (BT receiver, MAX board). they both need to be controlled by some MCU, something with I2S interface. you need to make sure that signal levels are matching (3V3?).
note that MAX board is both DAC and amplifier. next, any device will need some controls, at the very least that would be some sort of volume knob or equivalent (buttons, touchscreen, whatever).

one the architecture of core is working, it is time to look at power requirements of each module. with that, you can determine if buck or boost or something else is needed and where.

 

It was very scratchy and distorted and had a poor maximum volume. The goal with the redesign is to (A) put all components on a PCB board in attempt to decrease resistance and clear up the scratchiness and distortion and (B) properly distribute wattage through the design to make it louder.

If the problem was with the design, cleaning it all up and getting it onto a PCB probably won't accomplish these goals. A little experimentation first might identify the weak link. For instance you could try giving the amplifier a bit higher voltage. Do you have a breadboard to experiment with? It's a time-saving way to prototype before building. Radio frequency projects don't breadboard well but audio is fine. Higher current loops may need to go off-board but everything else is fine.

1. How do I figure out what specific parts I need?

This is one great challenge of designing - the possibilities seem endless. The first task is to define the goals of the project. For example, do you want a 3W amplifier or a 1W amplifier? What range do you want (ie. which bluetooth will you use). That sort of thing. The more specifications you can nail down, the more you can narrow your parts search. Sometimes the process is iterative, for instance if you find a component you like or already have, then you might tweak the design to accommodate that particular component.

From my understanding, I will need something to boost the voltage before sending it to the amplifiers as well as something to regulate/boost voltage into the I2S receiver and DAC.

Maybe. And it's likely you'll want some regulation to ensure steady operation as the battery voltage sags. You can buy little boost boards very inexpensively. For instance, I recently bought this one:
https://www.amazon.com/dp/B09MYQMMM4
The project changed and I never actually used it beyond experimenting to see how it worked. So I'm not recommending this part, just providing an illustration.

2. Can one boost converter (or whatever would be best fit to increase the voltage) be used for both amplifiers, or do I need one for each? If one can power both, then do I set it to double what is required by the boards in order to supply them both with max power? To me this seems like it would risk sending too much power to one of the boards and might destroy it.

You need just one converter for each voltage you need. Of course it needs to be rated to the power required. The load circuitry defines what power it will draw when provided a voltage source. Analogy: You can plug a tiny nightlight into your wall power and not worry about it having access to "too much" power.

 

clear up the scratchiness and distortion

Check battery voltage sag, amplifier clipping, grounding, bypass capacitors, and speaker wiring.