Tr505 Rythmn Imposter

The Roland Tr505 Drum Machine Mod:
The Rythmn Imposter

As featured on Florian Pilz' BetterGear/ BadGear Channel On Youtube.

The TR505 rythmn imposter is a pcb and an eprom that will replace the original sounds of the Tr505 with Sounds From The TR909, whether or not this is a good idea is up to you, but it exists and on this page you can find a little bit of information about it.

For the Love of God, WHY?

I did it because i could, not because i should have. The TR505 will never be a real TR909, but it still has a family resemblance and a bit of technological heritage.
The Tr505 with this mod becomes a useful addition to a live performance setup, is much more fun than a regular TR505 and will make cork sniffing analog purists have a heart attack on the spot.
Most of us will never own a real TR909, since we have better stuff to do, like eat, or pay bills. There are good clones these days, but there were a lot of TR505s made and not everybody who owns them wants to do 80s covers.

Who would do such a Thing?

Although i am the most guilty, a lot of the blame can be put on Lorenzo Vash, From Radiomechanica, a fantastic guy and a great synth technician.. He asked me to modify a few drum machines with 909 sounds and send me a TR505 to work with.
also to Blame is Harry Axten, who made a modification for the tr505 with sounds from digital drum machines like the DMX and Linndrum, showing that it was possible to do such a thing.

Update: version 2.1

I'm happy to announce that version 2.1 is now ready and available for purchase.
after the v1 pcbs were all sold, i decided to make a new improved version, which is now much smaller so you don't need to cut the flange from the standoff to make it fit., and has moved the eprom so that it can be fitted with a socket. all new boards from now on will be this design.

i hesitate to call this a kit, because there aren't any proper instructions.
if you can't fill in the blanks then you should find somebody to help you.

How do you do it?:

  1. Open the TR505

  2. Desolder the original Rom chip that contains the sounds.

  3. Solder in a couple of strips of female pin header in place of the oroginal Rom use as a socket (you can use a pcb socket,but i prefer pin headers because they are even lower profile)

  4. Solder male-male pin headers onto the rythmn imposter pcb

  5. Solder the eprom into the rythmn imposter pcb or fit a socket if you want to swap the rom later

  6. solder in 10k resistors

  7. connect a switch to change between 505 and 909 sounds. connect to sw1 on the pcb. on is tr909 sounds, off is 505 sounds.

  8. Put the rythmn imposter in the TR505 in place of the original rom.

  9. Close the TR505

i can fit the mod for you but you will need to send your me your tr505. in this case i will charge 80€ including all parts plus postage, to and from My workshop in turin. contact me if you are interested. you if can of course find a local technician to install it that's even better! or Lorenzo from Radiomechanica can install it for you.

If you buy this kit I assume you know which end of a soldering iron gets hot, if you aren't completely comfortable with desoldering a dip chip then I don't recommend that you try it yourself. It's easy to damage the pads on the circuit board, and it can be hard to fix if you do. I offer only the following guarantee: if you break it, then you get to keep both parts.

if you are a massive nerd and want to make your own eprom sets for the tr505 you can use this tool from r-massive: Rather frustratingly Thomas made this just after i'd finished putting together my eprom Image with a copy of audacity and a hex editor. for future Eproms i will use his software, it's much more fun than doing it by hand!

Prices are as follows:

Pcb only 20

EPROM chip with 505 and 909 sounds) 20

Pin headers : m-f m-m 10€( yes it's far too expensive, but I want to encourage people to find their own but still offer them for convenience).

you can pay via paypal to this email address:

contact me for shipping.

Images of the old v1 pcb.

Here is a nasty little video that i made showing the Prototype and the first home made Pcb. Florians video is much nicer. Many thanks to lorenzo from radiomecanica for finding me a tr505 to try this.

Version 1.5 eprom

i've just updated the eprom chip so that you can switch back to the original tr505 sounds.
for existing owners i can provide a replacement eprom chip. and all new kits now include the new Eprom.

39SF040 eproms

the Rythmn Imposter 1.5 pcb is designed to work with either 27c010 (one sound set) 27c020 (two sound sets) and 27c040 (four sound sets).

The following mod lets you use a 39sf040 flash eprom for 4 sound sets.