Quick Question about MidiBox Sid

Hi I’m building a Midibox sid with one core/one sid and possibly 2 sids.

My Question is, What is Audio In used for in the Sid?

Thanks

The designer of the SID chip thought it might be cool to “chain” multiple SIDs by connecting the audio out to audio in of another SID. But it doesn’t quite work that nicely since they’re a little bit too noisy.

Also, the audio in can optionally go through the filter (see “ExtIn” parameter in MIDIbox SID). This is useful if you want to filter external audio with the SID filter, or add a “feedback” pot so you get more filter resonance.