Adding Famicom Audio Channles To An NES Without Messing Up The Console

[Callan Brown] wrote in to show us a really interesting NES audio hack. [Callen] decided that he wanted the full Castlevania III audio experience, which (without modifications) can only be had through the original Japanese Famicom console. [Callen] weighed a few adapter options, and instead decided to come up with his own.

The issue is that the Japanese Famicom and the American NES actually have a different cartridge connector. The change in hardware from a 60 pin to a 72 pin connector added “features” like the 10 pins connected directly to the expansion port (used for stuff like the teleplay modem, who knew). The other two additional pins are used by the annoying 10NES lockout chip. While they were at it, Nintendo decided to route the audio path through the expansion connector instead of the cartridge.

This means that the Japanese cartridges can’t pipe sound to the NES audio channel with just a pin adapter. Good news though, after sourcing a pin adapter hidden inside certain NES games (Stack Up, Gyromite), audio can easily just be pulled from the adapter PCB. This requires the more expensive Famicom Castlevania III cartridge (Akumajou Densetsu). To cleanly route the new audio cable out of his front loading NES [Callan] reuses the sacrificial adapter game’s cart to make some kind of unholy hybrid. To round it off [Callan] also goes over steps to flash a translated ROM to the Japanese game.

What difference could an extra two squares and a sawtooth make? Check out the sound comparison video after the jump! Thanks [Callan].


25 thoughts on “Adding Famicom Audio Channles To An NES Without Messing Up The Console

  1. Seems like a lot of work.. If you’re crazy into NES games you probably want a disk system anyhow and from what I gather there isn’t a way to make them work on the NES. I would have just bought a famicom. ;)

    1. I am seeing too many replies like this here lately; hacking/modding like this is not necessarily about practicality or what you can buy to achieve an effect. its about ingenuity, resourcefulness, and creating a solution when you’re presented with a problem, buying things that are pre made and designed to function together is not hacking after all.

      1. I would add that hacking/modding is also more about using what you have to make it what you want. So if you have one version of a game (or any object) and have to go buy a different version to make it better than the one you already had, what’s the point in doing it? You might as well just buy the better one once you’re not satisfied with yours and just toss the one you already have. A good hack involves changing what you already have with other stuff that’s easy and/or cheaper to obtain, and most importantly, a challenge to think & work through.

  2. It sounds like there’s a lot of ‘coloring’ going on in the Japanese chip, but it definitely has a richer, fuller sound. Sounds very similar to the organ they wanted to portray in some parts, which I thought was impressive for an NES-era chip.

    On the other hand, I have no knowledge of chiptunes. :D

  3. It sounds like those extra channels are being used for a bass instrument (at least in this game) and it sounds like a solitary sine wave (that sounds like it was elevated an octave so it wouldn’t distort speakers?) is being used for the bass in the US versions.

    Using square and/or sawtooth usually gives far better tonality than a sine wave if you’re trying to make a bassy sound.

  4. Definitely a difference. I noticed a rumbling bassline in most songs and also a tremolo effect that seems to be available. Overall better note separation and a fuller arrangement. Nice job on the research and finding a solution :)

    1. What they neglect to mention here is that the Japanese version of Castlevania 3 has a Konami VRC6 chip inside the cartridge. The US version does not.

      This is the compatibility issue. The US pinout cannot handle the VRC6 since there is no direct route for it to the audio system. So it isn’t that Nintendo USA intended to cripple the NES. It just turns out that certain Japanese cartridges can’t be used on the US system the way that they were designed.

      As you can see on this link, there were very few carts that took advantage of enhanced audio hardware. Castlevania 3 just happens to be the most popular and best examples of this.

  5. Alternatively, you could make a custom 60 to 72-pin connector that routes to a couple of the extension pins to the Famicom audio pin, and have a small bridge device to put into the expansion port to connect the proper pins to the Audio In/Out signals and voila.

  6. Hey guys, thanks for all the comments. Yes Kaz, you could make use of the extension on the bottom of the NES console. Some people will actually just mod the console internally, and a 60-72 pin converter to work with no external changes at all. My goal was to create a cartridge-only solution.

  7. Im gonna go ahead and elaborate on what the differencs are and why, but before I do that, the short answer is that there are three extra instruments being used. Now for an essay’s worth of explanation! So, your standard US NES (and the japanese) creates music from a soundchip. The soundchip has 5 channels that are used as the instrumentation. These channels are Pulse 1, Pulse 2, Triangle, Noise, and a very primitive sample channel. Each channel can only play one note at a time, so if you wanted to add an extra instrument, your kinda screwed. Now the major difference between the US and JP versions of NES (or famicom) is that the famicom had extra pins which aloud for expansion chips. The specific chip used in here is the Konami VRC6. The VRC6 and other expansions are well known amongst the chiptune community for having two extra pulse channels and an exclusive saw wave channel for more dynamics. So theres you NES history lesson for the day….

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