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This is a Roland TR 606 drum machine with an external breakout box. The box features the following controls: Bassdrum PITCH, DECAY and TONE, Snare PITCH, DECAY and TONE, Tom PUNCH (switch) and individual TUNE controls, Noise LEVEL and Hihat FILTER. On its back are individual outputs for the instruments.
There is actually a small PCB with a completely redesigned Bassdrum circuit inside the breakout box. I still have the layout somewhere - I should probably dig it up and make it available to the DIY-community or the nice folks at the electro-music.com forums. I am toying with the idea of building my own drum machine, based on Marko Kanala's MR9090-Sequencer and an assortment of analog drum voices. The modded 606 BD would be a perfect fit.
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A great little box - sold on Ebay lightyears ago.