On Cartridge Sound Mixing

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Great Hierophant
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On Cartridge Sound Mixing

Post by Great Hierophant » Wed Jan 05, 2005 11:51 pm

According to my understanding of the Famicom's audio path, some cartridges can mix their on-cartridge sound with the Famicom's standard audio. It accepts the Famicom's audio output on pin #45, mixes it with with the cartridge based sound inside the cartridge, and ouputs the result on pin #46, which goes directly to the RF modulator or A/V outputs. However, that probably is not necessary, so the two pins remain connected and the extra sound is outputted along with the NES audio on pin $46,

Of the special sound chips, MMC5, FME-7, VRCVI, VRCVII, Namco 106 and the Famicom Disk System, which chip uses which method?

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Post by Quietust » Thu Jan 06, 2005 12:00 am

ALL Famicom carts use the pass-through method (Famicom audio comes in on pin 45, mapper sound gets mixed in, then the result goes out pin 46) - cartridges which do not use expansion audio simply short pins 45 and 46 together.
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Post by tepples » Thu Jan 06, 2005 10:47 am

Are there any Famicom carts that do any filtering of the Famicom audio? Is this possible, that is, can the cart sense the Famicom audio on the difference between GND and the audio pins?

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Post by drk421 » Thu Jan 06, 2005 7:47 pm

I've never seen a Famicom cart do anything with the Famicom audio.
It would probably cost too much to do anything with the Famicom audio, besides using a cap to roll off the highs.
Most carts I've seen just mix it using 2 resistors.

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