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  • Theory

    Theory of MIDI Valve operation


    4218 Jessup Rd., Ceres, CA 95307

    Phone (209)613-2148 FAX (209)634-2667

    Welcome to MIDI. Download from the internet or scan sheet music using the readily available software "Pinao Scan" or "MIDI Scan" to play our MIDI instruments. Musical Instrument Digital Interface. You can improve the response of your instrument as well as the selection of songs with MIDI. The paper roll slides over the tracker bar hole gradually until the incoming air overcomes the bleed of the pouch. This is somewhere around 1/3 open. The pneumatic responds and then the hole gradually becomes covered again until the bleed takes charge and the pneumatic is "switched off". With our MIDI valves, an electric signal of 12 volts causes the valve to open and overcomes the bleed instantaneously. Even marginal pneumatics find new life when the air signal is so close to the valve. Eliminate line resistance almost entirely by mounting the MIDI valve against the valve chest of your instrument. Since our MIDI valves are installed with a simple T connector, there is no intrusion. Installation is fast and simple. Simply cut the rubber tube near the pneumatic primary valve and insert our T and attach the MIDI valve to it. When the roll is stopped between songs and the tracker bar is covered the MIDI valve can take control. When the current is off it the valve is closed. The MIDI cable is about the size of a telephone cord with only 5 wires inside and you can run it for great distances without sacrifice.

    Theory of MIDI valve operation:

    Our valves are currently produced in 2 sizes. 1/8 inch for player pianos, nickelodeons and small band organs and 3/8" for large band organs either pressure or vacuum. All valves work on the same principal. A permanent magnet is attracted to the hollow iron valve seat. This insures closure when power is off. Synthetic rubber between the magnet and the valve seat insures quiet operation as well as good sealing properties. A coil wrapped around the valve seat/hollow electromagnet core repels the permanent magnet from it's seat when energized with 12 volts DC. 120 ohm for the 1/8" and 50 ohms for the 3/8". That's 100 Milliampere and 240 milliampere respectively.

    The 1/8" valve passes approximately the same flow of air as a normal tracker bar but can be attached closer to the primary valve which allows better performance. Because the MIDI valve can be mounted close to the primary pneumatic valve systems with larger bleed sizes (at least up to #67 drill size) can be converted using our small valve.

    Computer interface:

    In order to operate, each MIDI valve must be connected to an output board of a signal processor. This is like tubing a tracker bar. Simply start at the left side of the stack and attach to the left side of the processor board and start to wire. Each MIDI valve connects to ground and the other lead to the corresponding output. Some companies include outputs with their processors and some do not. We can sell you either. Once you have the wiring done you need something to play the MIDI file to the processor. The processor only interprets the MIDI bit stream for the output boards. You may use a simple and inexpensive MIDI playback recorder like the MDF-3 or a computer or lap top with MIDI output provide with the sound card such as Sound Blaster. We use this in our Monkey Organs because it operates on 12 volts and isn't much bigger than an ordinary book. You will need a computer and software such as "Cakewalk Home Studio" or "Cakewalk Pro" to transpose the MIDI files that you will want. If you have a modem you may download (copy to your computer) files from the internet from numerous clubs and arrangers for free. Transposing is then as easy as point and click. In 30 minutes I download about 90 songs and transposed 7 of them to play on our D42r MIDI calliope and it sounded great. You don't have to be a musician or a computer nerd to do this. It is fun and simple. All the directions are included with Cakewalk including a tutorial on CD-rom. So don't hesitate to start enjoying creation of your own song collection now. Cakewalk is available at any software outlet.

    MV125 Actual Size (Shown with a nickle)

    Universl MIDI interface (Processor)

    Board only, no case but with wire solder terminals and ribbon cables

    UMI-BB - has 128 outputs -

    MV375 - (not shown) it is much larger, 2" long by 1.6" wide. Click here for photo and description of application

    MV375P - Proportional version for expression -

    Outputs can be switched to inputs for recording. It's your choice. They must be connected to a keyswitch of some kind. You can use an inexpensive synthesizer.

    Last Update: Dec. 24 2011
    Web Author: Ken Caulkins

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