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Filter For Audio Application

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anirudha.athavale

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I want to design a filter for an audio application

which filter should i use ? Pi LC or RC and

other question was that should i use active or passive filter ????

i am using TPA3124D2 Audio amplifier. The output of the bluetooth module i will connect to audio amplifier through Filter

Kindly suggest me the filter circuit
 

barry

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It depends on your requirements, which you haven't specified. A passive filter will have loss; an active one won't. What are your frequencies? Do you need impedance matching? HP, LP, BP, BR?
 

anirudha.athavale

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After the Filter circuitry the signal is attinuated Do you know any reason ? after the output of bluetooth module u will find filter if i connect speaker directly to the output without filter the sound can be hear on speaker and if suppose i connect the speaker after the filter circuitry the siganl level is very low what u think ? do u know any reason as we are using RC passive filter in our Bluetooth based product

i am using the following schematic kindly suggest me any
 

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barry

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Are you connecting BLUE_SPK(+/-) directly to the speaker? If so, you are attenuating it because you've got about 10K source impedance driving an (8?) ohm speaker. At the very least, you are attenuating your output by a factor of .67 (the 4.7K and 10K divider)
 

anirudha.athavale

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I am not directly connecting the output of SPK(+/-) to the speaker, after the SPK(+/-) i am giving this input to the amplifier circuit i.e. TPA3124D2.....

should i need 1uf and and 10K.......

How you have calculated that attenuation factor....? 1- gain ?
can i directly connect the output of 1uf capacitor to the amplifier? will it afect loading effect. ?

---------- Post added at 11:43 ---------- Previous post was at 11:32 ----------

should i change the value for R12,R21 & R14 & R20
 

barry

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The outputs (SPK+/-) go to a voltage divider 10K/4.7K. Attenuation is 4.7K/(10K+4.7k) not including the filter.

The 1uF cap eliminates any dc offset on the output-it doesn't hurt. As far as what values are needed for the divider, it depends on:

1) The output level from the BTM1004
2) The input requirements of your amp.
 

anirudha.athavale

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output of the bluetooth module i am getting is 1 VPP.... and it is giving AM varriation in the output.....
 

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