Actually Equalizer doesn't need any special hardware, and proof of this is that all old Nokia basic phones like Nokia 6300 etc, all xpress music phones, and even Asha phones have equalizer built-in. But the problem in L520 is that it's firmware is not built to work with equalizer. The only reason that why Nokia did this is to show variation over Lumia series. If L520 has all features like equalizer, Dolby-Headphone(previously called Stereo-Widening Effect on XpressMusic phones), all those who bought L620 or 720 might have bought 520 instead of them, and Nokia will get loss by releasing them, so Nokia showed variation in firmwares of 520, 620, 720 because all of them have same chipset(CPU), same RAM, and same sensors, difference is only in cameras, gorilla glass, anti-glare screen. As double-tap to wake not worked in amber, but worked in Black update, I hope after next firmware update, equalizer works for L520(probably windows phone 8.1 update in april).
Originally Posted by Karthik Sampath
Also.. Glance screen doesn't require any special hardware.. it is Nokia criteria to show variations of phones, and also Glance reduces battery life drastically, this is one of the reason that Nokia doesn't give Glance to 520 or 620 because those batteries are small.