Hello everyone,
thanks to new payloads and new libctru branch by smealum and his team, we now have access to a lot of new services and i noticed RetroArch is now using DSP service for audio (lpp-3ds will be the next one, i'm working on it).
Anyway, in the future, a lot of homebrew will use dsp service for audio but to use it you'll need a DSP firmware dumped from a retail cartridge / eShop title and to do this the only solution at the moment is to pick code.bin file with braindump and process it with Retroarch to extract the dspfirm.cdc file you need (This problem happens only for NH 2.1 or lower users and CIA/3DS users).
This problem appears only for non-2.5 *haxs users cause new payloads have a built-in dsp firmware. What this homebrew does is to extract this firmware and let you use it on 3DS/CIA homebrews or on NH 2.1 or lower.
Thanks to @ihaveamac for the tests on *hax 2.5.
Latest version: 0.8 Download (Mirror): http://rinnegatamante.it