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Allen MOS1 and MOS2 Conversion Kits

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  • Allen MOS1 and MOS2 Conversion Kits

    I'm sticking with my current practice instrument for a while I think (A Conn Artiste 720, despite its problems which I have been unable to resolve), but I was wondering:
    I see a lot of kits for converting Allen MOS1 and MOS2 organs to MIDI on eBay, including kits to convert the stop tabs.
    The lowest cost I have seen is about $165, a small circuit board that literally just plugs into an edge connector that already exists on the organ:
    Supposedly it'll convert the keyboards and the pedalboard to MIDI

    And yet another device to convert the stop tabs:
    Both of these can be found on the Harrison Labs website (

    Is it really true that $260 can buy you an entire conversion kit for an Allen MOS1 or MOS2 organ, giving you the ability to so easily upgrade to a virtual instrument? (Plus the software and a computer to run a virtual organ of course). Or have I missed something?

    It was my goal for a long time to buy a digital instrument, but I'm starting to look more into the virtual organ. My church currently had an MOS1, this might be a good upgrade option in the future.
    My instruments:
    Home: A late 50's to early 60's Conn 720 (tube powered, of course)
    One reed organ; in pieces at the moment pending a helping hand to do some gluing.
    Two pianos (upright grand and a spinet) and an accordion (Hohner)
    Hammond A-105 with Leslie speakers
    1979 Allen 123-C (MOS1) digital computer organ

  • #2
    Not exactly. If you get the Harrison Labs MOS1 MIDI board, you'll want to get the version that converts all three divisions (great, swell, pedal) if you intend to MIDI the entire organ. I haven't used this one, but did use one from another company several years ago that is no longer available. Apparently it's not too much of a problem to add simple MIDI out to an Allen MOS1. This one from HL even tracks the transposer knob so your externally generated voices will stay with the organ's voices if you're playing them together.

    One extra device may be needed though, a MIDI merger. I believe the three divisions of the organ will come out on three separate MIDI jacks, so unless you are using three separate MIDI sound modules, you'll probably want to merge the MIDI streams into one. There are numerous sources for such a merger.

    As to detecting and sending stop-tab information, I don't think the other device you reference actually does that. It is simply an extender board that makes the stop information available so that you can tap into it. HL advertises a device that does convert this stop information into MIDI data, and I think it costs about $350 or so.

    If you can get your hands on a MOS2 Allen with multiple computers, our own Admin here on the forum and his Zuma Group have an excellent MIDI converter that can give you MIDI out on up to four divisions and it can be made to track the transposer as well (ask about it when you order). This will not work with the small single-computer MOS2 organs (125 and 225), you must have a 505 or larger because the necessary SDDS-Mux board is not present in the smaller models. This device does not transmit any stop or expression data, but Zuma Group may be working on something to do that.

    I used to have a computer attached to an old analog Rodgers with a MIDI adapter on one manual, and I used a touch-screen monitor to turn the stops on and off. That is actually a pretty good way to do it with virtual organs because it bypasses the mechanical and limited capture actions on older consoles.

    Keep us informed on your project. Sounds like fun!

    BTW, I used to have a Conn 720 and enjoyed it quite a bit. Loved the diapasons and of course the very pure flutes.
    Last edited by jbird604; 12-30-2012, 03:41 PM. Reason: correct HL info
    *** Please post your questions about technical service or repair matters ON THE FORUM. Do not send your questions to me or another member by private message. Information shared is for the benefit of the entire organ community, but other folks will not be helped by information we exchange in private messages!


    • #3
      Hello OrganForum!
      My questions is similar to that regarding the Allen ADC 2160A.
      Mine is an Allen 603 Drawknob MOS-1 two manual instrument. The organ has ceased working though the cabinet is in near-perfect condition.
      I wish to MIDI-fy (1) the Gt, Sw, and Ped divisions; and (2) up to 58 drawknobs + Sw-Gt, Gt-Ped, and Sw-Ped couplers. I installed three ALJ MIDI adapters for the keys but have had no success in the installation since there may be something failing in the Allen that precludes the ALJ units from sending the proper signals. (Probably will list the three ALJ adapters on eBay)
      So I am considering: (1) a Harrison 3-division adapter (around $250-270) for the keys assuming my Allen Keyboard Array board is not defective for its signals to be 'interpreted' by the Harrison unit. How do I determine that MY board is not defective?
      and (2) a Harrison stop converter ($350+) to send my drawknob signals to MIDI and thus to my Ahlborn Classic and/or Hauptwerk VPOs. (I will retain all the Allen Gen/Div capture and pistons/toe studs which function perfectly.)
      Any experience with these units in an Allen MOS-1 environment?
      Ultimately, I plan on three or four keyboards + ped with native MIDI and velocity sensing, of course, and abandon the Allen. Perhaps if I can make the beautiful 603 play its three divisions under MIDI - with or without the MIDI stop adaptation - I could provide it to someone wanting such an elegant two-manual console after it is MIDI-fied, leaving me to proceed with the component approach.
      Bob in S California


      • #4
        You should try to find out why the Allen has stopped functioning. If a power supply has failed, the keyboard arrays will also be down so you won't be able to use the HL MIDI adapter with it. The first and simplest thing to check is the power supply voltages on the big black power supply units in the floor of the organ. Your 603 will have two MOS supplies, both of which output -27 volts, + and - 5 volts. The voltages are adjustable via little pot shafts sticking out of the supply. You should check to see that the voltages are precise. Also put the meter on the AC scale and make sure that there is no more than a few thousands of a volt AC on any DC line.

        However, it's odd that the entire organ stopped working because a 603 contains two totally independent MOS systems. There are only a couple of things in the entire organ that are common to both systems. One is the delayed voltage that unmutes the audio. That little device is easy to replace and if that is all that's keeping the Allen from working it's a shame not to fix it. The other thing is the unregulated 12 volt supply in the organ floor, which is also cheap to replace.

        Of course it's always possible that both independent systems have problems, perhaps not the same problem in each one. In that case, you should be able to make at least one of the systems work by swapping the boards between them. I realize this is a little obscure if you're not a tech, but out in the field we almost never encounter an Allen organ that we can't get playing on the spot, especially a dual-system MOS organ like this.

        Anyway, good luck with your project. Please post your progress!
        *** Please post your questions about technical service or repair matters ON THE FORUM. Do not send your questions to me or another member by private message. Information shared is for the benefit of the entire organ community, but other folks will not be helped by information we exchange in private messages!


        • #5
          Power Supply checkout is coming next...

          Thanks, John, for indicating that there is hope for the native Allen!
          Stan at Harrison Labs today suggested the same PS check for starters, and I can do that. I still want to upgrade to three divisions of MIDI-OUT, initially to play my Ahlborn CLASSIC (with reverb that I always add) and later for Hauptwerk V.4 and various VPOs.


          • #6
            I have used that MOS2 board on my Allen 1105 3 manual, and can say it is awesome! I am very happy with it, and very thankful that Zuma group took the time to produce that for MOS2 instruments. Harrison labs has fine boards, and I have used them in a 301, but it is only for MOS1. Stan informed me that they really haven't had a huge market for MOS2, therefore haven't worked on one. I haven't had any trouble with my MOS2 board at all. Very easy setup. Hope this helps.


            • #7
              Hlabs organ Midi converters

              Hlabs is closing the Ebay store and has an improved site at where the user can pay using PayPal and/or Visa or Mastercard. They are currently developing a universal Hall Effect midi controller strip to work on any AGO sized 61 note keyboard and a universal 61 note input midi adapter.


              • #8
                I also have used the MOS2 board from Zuma on my Allen 1105 KDC and it works perfect. This is a very good designed and build board. Could not be happier.