Not sure what you taking about but with DENIM an equalizer was added to the 630/635
If you compare the two photo I attached, there's a surround eq symbol for youtube(IE) but not for songs(Music)
BTW, this is Windows 10 TP for Phones, but with Cyan update.
and YES, I got Denim update before I went for TP, but I didn't see the EQ option appeared in the settings ._.
Download audio from store and you will have EQ on Lumia 630.
Yes sorry on Denim.FYI there is no EQ in L630 running on CYAN ... EQ comes with denim update