If you've been itching for a system-wide equalizer for iOS, then you need to check out a new jailbreak tweak called EqualizerEverywhere
by iOS developer Reed Weichler.
This tweak adds an equalizer to iOS that you can use to control the sound bands of the sound your iOS device emits. It works in ALL of your applications, whether it's a third-party music application, your phone, YouTube, or anything else, and it integrates with Control Center.
You can manage the sound bands manually, or you can choose from a list of presets:
The presets you can choose from include:
- Full bass
- Full bass/treble