MATRIXSYNTH: Battery Powered TR-707 With Interchangeable TR-808 and TR-909 EPROMs

Saturday, November 28, 2009

Battery Powered TR-707 With Interchangeable TR-808 and TR-909 EPROMs

TR-707 Battery-powered with quick-swappable EPROM sounds

YouTube via rolandsh1000

"I think the 707 has some definite things going for it: great interface, lightweight, individual outs, onboard sound mixer pots, solid trigger outs. However, the things I always thought were odd were that it wasn't battery powered (such a lightweight chassis...why not?), and the sounds were good but not great (probably better than the 505 and 626, but the stepsister to the 808, 909, and possibly 606).

So this mod tries to fix both of those:

The first part is battery-power. I have an internal array of 10 AA cells that can be switched in and they'll power the unit for at least 10 hours. I use rechargeable NiMH cells for environmental friendliness. This enables sitting on the couch jamming with headphones and no wall wart leash!

The second part is a ZIF eprom socket mounted on the front panel where the M64-C memory cartridge used to go (something I know that I would never ever have used). This is wired into IC34 and IC35 on the voice board, which provide the ROM samples for all the drums except the crash and ride. Since IC34 and IC35 were 27c256 sized ROMs in parallel, they can be replaced with a single 27c512 64k ROM, which I've done here. No credit to me: Thierry on the Yahoo TR-707 group figured this out and posted his methods there for adding new sounds. To burn my own sounds, I got the WAVs from Hyperreal for the 808 and 909, downsampled them to ~22kHz and 8-bit, converted them to binaries, then adapted Thierry's BASIC program that organizes all the sounds into on 64K file per their stock organization in the TR-707.

This video shows me running from battery power (the only thing I plug in is the amp). I run through the exact same patterns using sounds first from a 27c512 EPROM with the stock 707 binaries, then my converted 808 EPROM kit, then finally a 909 EPROM kit (I didn't like how that last one turned out...anybody know of better sources for 909 sounds?).

I suppose doing the crash and ride eproms are next!"


  1. the "909" samples dont even sound like 909 samples to me

  2. This comment has been removed by the author.

  3. Oops I deleted my comment....I can sample my own TR909 if you like ;)

  4. This is fantastic - I'd love to know if you could make this process something available to others - for $$, of course. Or at least sell the detailed instructions for users or their techs to implement.

    Bravo! I've always loved the 707 for it's true 808/909 style of programming, but the sounds have always left me a bit deflated. Mine only gets used as a sequencer for other drum samples - this would certainly breathe more life into it.

    Again - thanks for this great post!

  5. Hi Vicks,

    the process to install the socket isn't all that bad. some desoldering of the voice chips, then soldering those pads in a particular order to the socket, then installing the socket.

    and better software engineers than I could come up with a simple executable that takes 12 WAVs and converts them directly to a single 64k binary that you burn to an EPROM.

    maybe Diabolical Devices could do it - they seem to do a good business modifying 707s...and I wonder if more folks would prefer an 808-kitted-707 than a bent-707! ;)

  6. jasonnova

    I got those 909 samples off Hyperreal, but I've never used them in anything else, so can't say if it was my downsampling process that goofed them up or whether they just aren't too great by themselves?

    I might work on this a bit more...

  7. i actually suspect they arent all tr909 samples, great job on the 707 regardless :-)

  8. Fantastic job, well done!

  9. Great Modding job!
    That 909 is a bit off yes :)

    Here are 2 TR909 kits in wav, I used em to make the (now factory installed) Radikal Technologies Spectralis TR-909 drumkit, so I suppose they are good enuf :0


  10. i'd really like this mod for my TR-707! how hard is it to do? couldn't you write some instructins? :)

  11. That's awesome! I do love the stock 707 sounds, but the ability to add more samples to it, hell yeah! And also, those are by no means 909 sounds. Down sampling wouldn't have made them sound like that.

    I would love to see this commercially available!

  12. The mod is nice, but it could be nicer: If you have a 27C512 binary (64K), you can put two binaries in a 27C010 (128K), four binaries in a 27C020 (256K), eight binaries in a 27c040 (512K). Connect the common address/data lines in the place of the eprom and pull all not used lines to ground thru 10K resistors. If you use a 27C010, you would pull pin 2 to ground and to key between bank 0 and bank 1 you would connect 5V to this pin. This is an easy task, I can draw a diagram if you're interested. So you won't need to change EPROMs, all programs will be inside the toy

  13. I would be interested, unfourtunatley i'm not able to burn eproms...

  14. to Alexandre Souza - yes draw this up post it somewhere - pretty please :)

  15. can we get the program ? (end if you are realli otivated the pinout?) i'm really interested on this mod nd i don't found any sot or schématics for him ;'/

    really good job!

  16. i have just purchased a tr-707 , hoping that i can find the right resources so i can purchase a interchangeable tr-808 EPROM. please contact me at


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