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Location of Gain Control

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  • Location of Gain Control

    Can you tell me if the amplifiers on an Allen AP2 have gain control and if so where to find them. Thanks.

  • #2
    An AP2 probably has an ordinary ADC amplifier in it, which will have two knobs on the front. I'm guessing that model is MDS technology with either a W4 or W5 cage for the tone generator. If so, there will also be a gain control for each of the four stop groups, and there should be a chart inside the console to show which stops are in which group.
    John
    ----------
    *** 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!

    https://www.facebook.com/pages/Birds...97551893588434

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    • #3
      Originally posted by jbird604 View Post
      An AP2 probably has an ordinary ADC amplifier in it, which will have two knobs on the front. I'm guessing that model is MDS technology with either a W4 or W5 cage for the tone generator. If so, there will also be a gain control for each of the four stop groups, and there should be a chart inside the console to show which stops are in which group.
      Yes, it is MDS technology. There are no knobs on the front of the amplifiers. They are not caged.

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      • #4
        According to the Allen tech site, the AP2 could have either the M2 amp (with a pair of volume-control knobs on the front) or it could have the M5 amp, which is a later version. In either case, the amp is the metal assembly on your left in the floor of the console as you look in from the rear.

        If you have no knobs on the front of the amp, then it must be the M5. On the M5 amp, there are two of the little miniature screwdriver pots I was talking about, and they are located side-by-side on the left-hand end of the assembly, either on the front or on the top of the unit. They are only marked with "CH1" and "CH2" to designate which channel each one controls. Turning the pot clock-wise increases the gain, CCW decreases.

        Since there are no numbers to go by, you have to guess about the setting by seeing where the slot or (on some pots) the pointer points. Straight up 12:00 will give you a moderate amount of gain, but you may need to turn it up quite a bit higher, perhaps to 4:00, depending on the size of the room. The pots are a bit delicate and so turn them carefully, applying a minimum of pressure and being careful not to turn past their minimum and maximum positions. If in doubt, just apply the slightest amount of turning effort in the CCW (softer volume) direction, which should immediately let you know where the pointer is pointing.

        Remember that the level of each stop group is also determined by the settings of the pots for that group on the W5 tone generator assembly. If you have some stops that are way too soft or out of balance, you may need to go through the voicing procedure to get all the stops in correct balance with one another.

        If you don't have either an M2 amp or an M5, then someone has put in a different amp, which would be peculiar indeed. Post a pic if you still don't seem to find what you're looking for.
        John
        ----------
        *** 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!

        https://www.facebook.com/pages/Birds...97551893588434

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        • #5
          Thanks so much. I will check it out Sunday. So appreciate your help.

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