Could someone help my analyze this audio/bluetooth board?

Thread Starter

sam68

Joined Mar 2, 2017
41
I have several of these small audio amp boards so I don’t mind damaging some to get to my end result;
1. There will be two of these boards in my portable speaker unit. The first board will drive other speakers and also drive this 2nd board which will drive four 1.5” speakers dedicated to 80 to 160 hertz for near field listening.
a. No problem doing that with a line in high and low pass filters before going into AUX but how to do it if incoming Bluetooth.
b. I could put HF/LF on the speakers output but that is not the ideal solution (large inductor, etc)
c. So what do you think? Being a newbie on circuitry, could I change out one or two of the 470 uf caps for larger caps - Maybe that would limit the higher frequencies? or
d. Is there a way to find on the board where the circuit outputs a pre-amp signal, then cut it, plug in my hF/LF circuit there then back into the board? But where?

BTW: this is a TPA 2017D2 3 watts per channel chip with AGC, compression and limiter built in. It is located at the bottom of the 2nd picture.
Thanks for any help.
 

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Thread Starter

sam68

Joined Mar 2, 2017
41
Thanks Dana for your response. I don't think I can understand how to do a linear filter and I'm not sure if I can cut the chip leads on the board. I was hopeing that I could find two places on the board where I could solder the entry of my filter or change out the caps (not sure that would work.)
 

danadak

Joined Mar 10, 2018
3,630
A filter design tool here -

https://www.electronics-tutorials.ws/filter/filter_4.html
https://webench.ti.com/filter-design-tool/
You would cascade (for passive only filter) a high pass then a low pass RC
filter.

I think you will have to use a piggyback type of construction, filter on small
board mounted above area where the inputs to the Class D amp are. You can
always construct the filter in the "air" as a method of construction, and hot glue
the assembly. I would first try this away from board to see if the hot glue
affects filter performance. To confirm filter is doing what you want.



Regards, Dana.
 
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