Expansion Port Sound Module (EPSM)


Please read the 2nd Batch notes below.

In stock




  • Because of the amount of time it took to produce the product there are far more people on the wait list then units in this batch.
  • This is a brand new product without much software that uses it yet. The goal is to get this these units into the hands of people that are writing homebrew, tools, music and testersĀ  to make the tool usable for a wider audience.
  • The connectors on these modules are made by processing existing connectors with many tools. Because of this the fit and finish differs on each unit. This means some units slide with a loose fit and others with a tight fit. This is something we hope to fine tune in the future.
  • A Famicom version is also being considered. If you are interested in a Famicom version please register your interest here.

1st Batch Notes

  • The first batch can be identified by a black pcb with a green led.
  • Although EPSM output is available through the rca and rf jacks. The audio levels are incorrect through this route and using the 3.5mm audio jack is recommended for the best quality and experience.

2nd Batch Notes

  • The second batch can be identified by a black pcb with a blue led.
  • There was a small issue affecting some units in this batch. Some areas of the soldermask was too thin and removed during cleaning. To prevent corrosion these areas were plated with solder. These units are functionally fine.
  • EPSM functionality is only available through the 3.5mm jack and not through the RF or RCA audio jacks.

Expansion Port Sound Module (EPSM)

The Expansion Port Sound Module, EPSM for short. Is a new device made for the NES Expansion Port that has never really been used.
This device started with the idea to make something useful for the never used port.
The basic idea is to add a lot more audio capabilities to the NES without having to add expensive hardware to each and every cart,
while also adding support to listen to the already existing carts with expansion audio.
Using game carts with expansion audio on an unmodified NES will only output the audio into the void, the EPSM solves this.
It’s cheaper to get a slightly pricier expansion adapter than adding audio hardware to multiple games.
The EPSM would have been possible to make as early as 1985 though in a bulkier version since the slimmed down version of the chip did not come as early.


  • Genuine Yamaha YMF288 FM Synth Chip
  • Adds 15 new sound channels to the NES for future homebrew support
    • 3 Square wave channels, also capable of noise
    • 6 FM Synth channels with Hard Panning Stereo support
    • 6 Rhythm channels featuring 6 different ADPCM Drum Recordings with Hard Panning Stereo support
  • Forwards expansion audio from supported gamecarts
    • Original Famicom expansion audio games with compatible adapter
    • PowerPak
    • EverDrive N8 or Everdrive N8 Pro
  • 2 different Addressing modes
    • Direct/Mapper assisted
    • Fallback mode
  • 3.5mm Jack for Stereo Output

Cartridge Support

Direct mode addressing requires an Everdrive N8 Pro with this mapper pack is required for EPSM support. Special EPSM specific cartridge boards using direct addressing mode is planned. You can sign up to be notified of the first one planned here.

Source and Support

Please note that although this is an open source noncommercial project Muramasa Entertainment has received permission to manufacture the EPSM from Perkka the creator of the EPSM. Please note that support is limited and before purchasing please check the Github page to see more information on the product. Also please feel free to ask questions on the NESDEV Discord on the #chiptuning or #hardware channels.


If you would like to see some examples of what is possible you can listen to this playlist from how2Bboss here.

Additional information

Weight0.0625 lbs
Dimensions3.75 × 2 × 1 in


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