Ensoniq EXP-3 Hacking

The EXP-3 card is an expansion card for the Ensoniq MR Series synths, and also the ASR-X's. It has 24MB of Urban Dance sounds. There are other EXP cards available. This page is my attempt to document the card, so users can eventually make their own custom exp cards!

The EXP-3 contains 8 chips total:

  • one 2Mbit EPROM
  • one 74138
  • six 4MB PROM's.

    The card overal has two large headers on it:

  • (P1) 2x20 EPROM Header
  • (P2) 2x25 Sound ROM header

    Each header seems distinct from the other one. The smaller header has only EPROM signals on it. The larger header has only Sound ROM signals on it. At this point in time, I have documented the pinout of P1. Hopefully someone out there will use this information to read out the contents of this EPROM!

    There is also a 74138 1-of-8 decoder on the board. This is attached to the larger header and used to select which one of the sound ROMs to talk to.


    The EPROM is labeled U8. it's a TI 27C020-120. That means it's a 2Mbit (256KB) EPROM with a 120ns access time (very slow!). My guess is it contains information about the SoundROM's, like the names of the songs, and about the card in general. A read-only device, it is connected to the 68340 CPU through a motorola 253 buffer chip on the Gizmo motherboard.

    My EPROM has a sticker that says "EXP3 DANCE E507 cksum" on it.

    Here's the pinout of P1.

    Here is a link to the EPROM Spec sheet. (btw, TI doesn't have a link to it any more, so that's the same AMD part.)

    Sound ROM's

    These look to be typical Ensoniq SoundROM's, like this link. The ROM's on the EXP-3 are labeled 135100111N, where N is a number from 1-6. They also have the name DANCE X on them, where X is a letter from A-F, corresponding to n.

    They have 44 pins apiece. This is my my guess at their pinout setup...

  • 1 pin for chip select
  • 1 pin for read/
  • 21 pins for address. (4MB= 2^22 byte addresses, or 2^21 16-bit addresses)
  • 16 pins for data.
  • 1 pin for power
  • 1 pin for ground That's 42 of them accounted for so far! I wonder what the rest are? If you have specs, please, e-mail me!

    Back to synthesizer hacking


    If you have anything else you like the smell of, e-mail me and if I like it, too, I'll add it. shifty@gweep.net