The WP support says that it should be available under the 'Audio' menu in settings, but it's not. It doesn't make sense how the Lumia 620 was an infinitely superior device.
EDIT: The equalizer is now available with the new Denim update.
Hey buddy good news for all of u. I have faced this problem over a week. Solution is update your lumia after that you will get equalizer in audio setting. It will take approx. 1 hr and the "phone update" option is located in "setting option".:smile: