The new audio chip is an incremental update of the old SPU called... SPU2! Improvements include the inclusion of 2 MB of internal memory and 48 channels available (two times the original amount).
The SPU2 is made of two sound processors inside, referred to as CORE0 and CORE1, and runs at ~36.86 MHz. Each one processes 24 channels.
Curiously enough, these are still two independent processors and to configure them, you have to alter their registers. However, Sony warned developers that both sets of registers have to be set with 1/48000 seconds of gap. If you hurry too much, the behaviour of the SPU2 becomes unpredictable!
The SPU2 inherits the same effects available from the original SPU. The memory provided is used as a 'work area': You can store raw waveform data and allocate extra space to process it and apply effects on it.
Finally, the chip can mix all channels to provide stereo output. Now, here is the interesting part: The SPU2 can feed itself the mixed stereo sample as new input, this enables the EE to access it (to mix it with even more audio, for instance), or keep adding more effects (such as reverb, echo and delay).
Video - Kingdom Hearts II (2005). Without reverb.
Video - Kingdom Hearts II (2005). With reverb.
Audio out
The audio signal is outputted through two media:
- Digital Audio: Referred to as the Sony/Philips Digital Interface or 'S/PDIF'.
- Analog Audio: Goes through the digital-to-analogue converter and ends at the Multi A/V port.