If what I read is correct of the chip tda2822 If you reduce the supply voltage it will bring the amplification down accordingly. Pin 2 is Vin. See page 5 http://www.st.com/content/ccc/resource/technical/document/datasheet/9e/18/f7/cd/2e/b8/43/62/CD00000134.pdf/files/CD00000134.pdf/jcr:content/translations/en.CD00000134.pdf
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