Firstly, the MIDI bass pedal electronics have been cast in stone (or, at least, cast on a small PCB)...
![](http://1.bp.blogspot.com/-dQ5s37oibgY/TcVQ09E6u5I/AAAAAAAADwk/WdzlhbK--QE/s400/Pedal%2BElectronics.jpg)
Next, I purchased a bunch of linear potentiometers from a trader on eBay, and made up a PCB to take nine of them (enough for a single manual). Here's the set...
![](http://2.bp.blogspot.com/-AicmH_OJuNU/TcVRRZrBoqI/AAAAAAAADws/d0SLo2elna8/s400/Set%2Bof%2BDrawbars.jpg)
Readers may recall that I've explained how my drawbars are scanned - but I needed to make up an interface (having previously only breadboarded the solution for 5 drawbars and a single additional analog control). I designed an interface to service a set of 9 drawbars and another set of 5. Two of these units will be needed - one for the swell manual & pedals and another for the great manual and miscellaneous analog controls.
Here's my schematic...
![](http://4.bp.blogspot.com/-56mf6CxY7s8/TcVSFW__ikI/AAAAAAAADw0/YletStMr1nM/s400/Drawbar%2BInterface%2BSchematic.jpg)
I elected to use the A733 PNP transistors I salvaged from the "Donor Organ" - not only as a signature "cheapskate" joke, but also to ensure that authentic Hammond sound!!!
Here's the finished unit, made up on some nice white PCB board I picked up at the NARSA rally...
![](http://2.bp.blogspot.com/-6KvgZmizcT8/TcVSvdF9dlI/AAAAAAAADw8/XJaie2_deOs/s400/Drawbar%2BInterface.jpg)
So - here's a shot of the "organ" development to date (sans pedals, which are hiding out of view)...
![](http://2.bp.blogspot.com/-c_Gnne3LHgs/TcVTUC-KNgI/AAAAAAAADxE/RUhpzvL5mN8/s400/Organ%2Bto%2Bdate.jpg)
You can even see the lunatic Leslie Switch!
I have the new drawbars AND the original 5 "test" drawbars running (the latter now configured for the lower manual).
Just as I finished the new set of "potentiometer" drawbars, a genuine set of Hammond drawbars came up on eBay. I snapped them up and will be fitting them to this project. Real drawbars are nine-position switches (rather than potentiometers), so an entirely new interface methodology will be required - but it have been fun developing this one (and I can still use it to implement general analog controls).
Watch this space to see the real Drawbars.
...-.- de m0xpd
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