Cartridge port sound input

This is an archive of a topic from NESdev BBS, taken in mid-October 2019 before a server upgrade.
View original topic
Cartridge port sound input
by on (#220838)
I see that the cartridge has an entrance of sound, is possible to use it like entrance of DCPM or similar?
Re: Cartridge port sound input
by on (#220840)
Only the Famicom and Famicom-like devices have the ability to mix in audio.

Other than the FDS, there were only a few games that added expansion audio music, and another small handful that added dedicated speech playback ICs.
Re: Cartridge port sound input
by on (#220871)
On the NES, Nintendo expected audio to be mixed in on the expansion port. It's far too expensive to make the connector in a small quantity (other than labor intensively by hand, as Chkyn was doing), but at least for audio, INL has come up with an (IMO) brilliant idea for a jumper board that can just slot in and connect the audio pins. It's very inexpensive to build, can be as few as 4 parts if you used a fixed value for the mixing resistor. I'm still holding out hope that all NES systems' audio have roughly the same amplitude.

In other words, I think it's a good time to start talking about audio input on the NES. I've got a couple audio projects in the works.