via
this auction
"An Electronics Project With A Difference. Build Your Own tr-909!
If you've ever wished for the warmth and flexibility of an original analogue drum machine like the TR-909 and you're also handy with a soldering iron, then a real alternative could be to put one together yourself. The 9090 project starter kit contains what you need to get started. This is a project suited for more experienced electronics enthusiasts and requires a small number of obsolete components.
The 9090 Project is an authentic sounding, rack-mounted, MIDI controlled copy of the TR-909, that you build yourself. The starter kit being offered for sale in this listing contains the bare printed circuit boards and a small number of special components. The majority of the electronic components are to be obtained separately from your own preferred electronic components supplier.
The advantage of using these boards is that the hard work has already been done: well thought-out, compact and extensively tested board layout design makes them an absolute pleasure to build, and the end result looks fantastic. These PCBs contain zero errors, therefore fitting all of the components and doing all of the wiring correctly can often result in something that works pretty much straight away..."
Descriptions for the following six circuit board pics in order:
One: "Board One - Contains power circuit, noise sources, bass drum, snare, low and mid-toms"
Two "This image shows all of the parts you get together: Three PCBs, PIC microcontroller and three PROMs"
Three: "Board Two - Contains power circuit, noise sources, bass drum, snare, low and mid-toms"
Four: "Four chips supplied: PIC Microcontroller contains embedded software for the MIDI interface, and three PROMs contain data for the hi-hats and cymbal sounds."
Five: "Board Three - Output sockets / audio mixer"
Six: "High quality silkscreen makes assembly easy."
"Features
□ Includes all analogue sound circuits from the original machine, and it sounds identical. Even better, in fact - because some of the sounds have more flexibility. The Bass Drum, for example, has a number of new additional control knobs that enable it to make a fantastic range of kicks. Take a listen to the Sound Samples on the right (mp3 format).
□ It does not have a sequencer of any form, but it has an excellent full MIDI interface. The PIC microcontroller that comes supplied with the boards is pre-programmed with embedded software that forms the heart of the MIDI interface (decodes the MIDI messages and translates them to trigger and velocity signals for each drum circuit). The drum sounds are velocity sensitive. How the drum sounds are mapped across the keyboard scale can be reconfigured via System Exclusive messages. LED indicates MIDI activity.
□ A 'bonus feature' is a Sync24 output, which enables you to sync something like a TB303 or MC202 to the MIDI clock via the 9090.
□ The boards are intended to be built into a 19” rack enclosure or a sloping-top box (or whatever you choose) to form a MIDI controlled 909 clone. It's entirely your call on what shape and size yours is going to be! You can also choose to only build some of the drum circuits if you don't need all of the drum sounds.
I kept most of the sound circuits pretty much as they were in their original form, and the project includes all of the sounds found on the original machine. Some of the sounds have been enhanced to expand their capability far beyond those in the original machine, the Bass Drum being a good example: it now has seven potentiometers instead of four, and sounds absolutely awesome. I think many people built their 9090s just for this sound alone. Some original components that have become long obsolete have been replaced by easily obtainable substitutes, without affecting the timbre of the drum sound in any way.
All of the sound circuits are built onto the two main large boards that are seen in the picture. The third long, narrow board is used to mount the rear output sockets onto (featuring individual and stereo summary outputs). I used two main boards instead of one because it means that you can stack the two boards if you want to build the project into a relatively small enclosure, and they’re just easier to work with. The boards also contain the MIDI interface, output mix amplifier, power regulation circuitry and even a handy DIN Sync output so that you can use the 9090 to synchronise your TB303 or MC202 to MIDI clock. The completed boards just need potentiometers and output sockets wired to them, power supply and MIDI input, and away you go – a fantastic analogue drum machine you built yourself."
Further details and samples at
the auction and
here.
Update: some audio vids via MB909 in the comments
here.
flickr by Chris_Carter_ 
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