Sekhar
You are manufacturing commercial SMPS units, I don't think this is welcomed here.
You should at least tell every body about your plans, or go and do the research yourself, rather than asking for free help.
Simple Tone Control
Hi
I give you good simple circuit. you may need to put another OP-AMP to make some amplification to the signal AFTER the Eq circuit.
Test it on bread board, and tell me results.
Its amazing circuit!
:)