diyAudio - Lm3886 passive bass boost

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Lm3886 passive bass boost

I found this site

LM3886 Gainclone 2x68 Watt Full Amplifier Project

Does anybody tried this circuit?

If we boost the bass on lm3886, does it affect the rest of the frequency band?

Hi,

I've downloaded the Overture Design Guide xls file.

I'm trying to understand the negative feedback circuit.

Can someone elaborate the function of C3 & C4?
Which part of the circuit actually boosted the 30-70hz?

If let's say i need to boost higher(12db) and more bandwidth(30-100hz) , which component should I change?
Do I lower the gain by increasing the Ri to 2k ohm to get 12db+ bass boost?

According to the schematic, 30hz gain is 34db. From the design guide, I just do not get the correct value or something is missing in the circuit.

http://www.circuit-projects.com/cimg..._schematic.gif

Thanks in advance