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  • Allen "Special" MIDI Project

    Howdy. I usually play an old Estey pump organ, or the piano, but I have been wanting to learn some classical organ, so......

    I just brought home a really nicely-cased minty Allen T-12a (though the nameplate inside says "Special") with the princess pedalboard (I know, I know, but the price was right and I didn't have to transport it very far... lol) for a MIDI project. I feel a little bad about gutting a working organ of a certain age, but it just has a single rank of flute oscillators and sounds pretty bleh. No chiff or anything, just sine waves I guess. And it's in desperate need of tuning; seems like it gets consistently flatter the higher you go. I do plan to keep all the internal speakers (especially the "gyrophonic projector") and amplifiers, and possibly the manuals (through I'd like to have velocity sensitivity for certain things too, and I am afraid that running those whisker contacts at less than 24v will cause problems eventually).

    I'm planning on MIDIfying it myself, building my own encoders on perfboard with 2 or 3 "teensy++" Atmel microcontroller stamps, chained together serially to pass the MIDI stream along, with one master USB-MIDI port hanging out the back. Although the two manuals, the pedalboard, and the stop tablets + swell, and maybe a relay to engage and disengage the rotary speaker, will appear as separate MIDI devices. I am hoping that I can get jOrgan running on a Raspberry Pi 3 internally for synthesis, with a small USB touchscreen mounted somewhere, though I'll be using some external synthesis for general patches too. I wish Hauptwerk were more embeddable.

    I'd like to fix up the rotary to be variable speed, too. I haven't looked at it closely yet, but if it uses a DC motor then I could probably rig up some sort of PWM deal to do that. But if it's an AC motor, then I'd probably have to switch out the motor for a DC one, and that might be a lot of trouble...

    The organ also came with a Wurlitzer rhythm box, which is pretty terrible haha. I 'spect it will go in the junk bin, or I'll recycle the controls into something else.

    The cabinet is really nice, though. Anyway, I'll start a build thread in the appropriate subforum when I start this project, though I have a couple other projects I need to finish up first.
    Last edited by Mr. Polecat; 10-20-2018, 08:57 PM. Reason: hit Enter too soon!
    1914 Estey Parlor Organ. 196x Allen T-12a "Special" (MIDI VPO project). Digital piano. Various guitars. Autoharp. Banjo. Bowed saw. Musical Cat.

  • #2
    Some of those parts may be valuable to others. Especially that Wurlitzer drum machine.

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    • #3
      The drum machine is a "Swinging Rhythm" unit, and is not in very good shape. The case is coming apart at one seam and it has some electrical issues. But I will keep it around and give it away here if I don't use it for anything.

      At first I'd assumed it was just a multi-track tape loop in there, but the pitch doesn't change as it is sped up. So there must be something more interesting going on in there. I wasn't aware that there were any drum machines like that around in the 1960s when I'd assumed this organ was made/purchased. There is some Allen sales literature from the early 80s in the bench, but I didn't think these T-12 type organs were made past the 60s. Certainly they wouldn't have still been selling them in the 80s? O_o

      Perhaps the drum machine was added later on.
      1914 Estey Parlor Organ. 196x Allen T-12a "Special" (MIDI VPO project). Digital piano. Various guitars. Autoharp. Banjo. Bowed saw. Musical Cat.

      Comment


      • #4
        Originally posted by Mr. Polecat View Post
        The drum machine is a "Swinging Rhythm" unit, and is not in very good shape. The case is coming apart at one seam and it has some electrical issues. But I will keep it around and give it away here if I don't use it for anything.

        At first I'd assumed it was just a multi-track tape loop in there, but the pitch doesn't change as it is sped up. So there must be something more interesting going on in there. I wasn't aware that there were any drum machines like that around in the 1960s when I'd assumed this organ was made/purchased.
        The Wurlitzer Sideman was the world's first drum machine. It was vacuum tube based with the drum patterns programmed into spinning mechanical disks. Introduced in 1959.

        http://synthmuseum.com/wurl/wursideman01.html

        I don't anything about the "Swinging Rhythm" unit but it was undoubtedly newer technology than the Sideman.
        -Admin

        Allen 965
        Zuma Group Midi Keyboard Encoder
        Zuma Group DM Midi Stop Controller
        Hauptwerk 4.2

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        • #5
          The T-12's oscillators are individually tunable, so you might be able to tune it right up. Just use a free or cheap cellphone app like "ClearTune" and tune them one by one. It's of course just one extended "unit" generator. The lowest note of the 8' flute is marked "C1" and it goes up from there. Don't use any of the synthetic stops, such as diapason, string, or reed tones, for tuning, as these turn on numerous oscillators with each key. But if you tune the entire 8' scale, then switch to the 4' and 2' flutes to tune the extended pitches, you'll get it done in no time.

          The 16' octave is marked "C0" through "B0" and can be tuned by playing the bottom octave of the pedals on the Bourdon stop. Note that a soft "G" tone will play with the "C0" (and likewise up through that bottom octave). You have to ignore that sound while tuning just the fundamental pitch.

          If any oscillator will not tune all the way up to pitch, the cure is to remove the smallest tuning cap (with a value like .01 mfd or even smaller), which will immediately raise the pitch by quite a bit. If it goes so high with that cap removed as to be above tuning range now, you have to substitute in a slightly smaller one, maybe try .007 mfd or so. Never change or tinker with the larger tuning capacitor, only the small "trim" caps. Allen used to sell a tuning "kit" for analog service which contained a large selection of these trim caps in many values so a proper one could be found for any off-pitch oscillator.

          An oscillator that will not speak probably needs a new keying capacitor. These are lined up along the edge of the generator, and values run from about 2 mfd through 15 mfd. These control the speed of the attack, so the low pitches get larger caps for slower attack.

          The little T-12 type organs aren't much, but they can make some pleasant music. Unfortunately, the AC single-speed motor can't be run at any different speed, so it's either Trem on or Trem off. I suppose a person could wire in a switch to turn the motor off at will, to get a sort of de-celeration effect, but I've never tried that. Cheaper and easier to set it up with a Neo-Vent if you want both fast and slow effects available.
          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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          • #6
            Thanks for the info!

            As I've been thinking about the project more, I think I'm going to leave the oscillators in there instead of gutting them out. But I'll disconnect them from the manuals when I do the MIDIfication. Once it's working as a controller, I expect that I can probably use a couple of Teensys in parallel, communicating serially, to switch a bank of transistors that will supply the 12v (I assume) key voltage to the old oscillator units. Then I ought to be able to use the Teensy USB-MIDI library to turn it into a MIDI-controlled dealio. Not sure how useful that will be, but it will be a fun/fairly-cheap project, lol. To get the layered harmonics of the more "complex" stops, I imagine I can just switch on multiple oscillators and fix up some kind of thing with program change messages to select which combinations of harmonics are to sound.

            I think maybe I'll also try to MIDIfy that drum machine, for giggles. Which I 'spect will be easier/cheaper than doing the oscillators in the organ haha. Kind of a cheaper test-run.

            The more I think about it, the more I think I'd be better off to remove those whisker-contact manuals and replace them with the innards of a couple Keystation 61s. I'll get better reliability, and velocity sensitivity when needed. The original manuals are just molded plastic keys anyway; not any sort of wood-core or anything that would be a shame to lose.

            I haven't looked at the horsepower rating on the rotary motor. I am hoping I might be able to use a windshield-wiper motor (or other somewhat powerful and easily-available 12v DC motor) and turn down or sleeve the shaft to mount the pulley off the old motor to it. Then a fairly beefy power transistor to switch 12v to it, while generating a PWM signal for it on one pin of a Teensy, in software. I am not sure if I ought to put a speed sensor on it or not, although having one would allow the PWM software to self-adjust to maintain a specific RPM instead of just guessing at it. This might be useful for matching the rotary to a multiple of a specific tempo or something equally silly. I 'spect I could glue a cardboard wheel with a notch in it to the big pulley, and use that to trigger an optical sensor to count RPMs. That would probably unbalance things less than gluing a magnet somewhere and using a hall effect switch. Another alternative might be to use a big stepper motor to run the rotary, but I am not sure they make any powerful enough for something that big (at least not commonly available), and I'm not sure one would run fast enough without changing pulleys. I know I certainly don't have any stepper motors that big in the junk pile! I'm also worried that the presumptive 12v supply for the key switches and oscillators won't be able to source enough current to run the motor too, but I suppose I can just install another power supply for that if needed (I don't have a suitable one in the junk pile already, though ).

            The most involved/annoying thing will be MIDIfying the pedalboard, which I probably ought to use hall effect switches for. I am pretty dubious of operating those whisker contacts at 5v. I'm still trying to decide if I ought to just use one hall effect switch per pedal, or two (velocity sensitive). At first thought, velocity sensitive pedals seem a little useless and over-complicated. But on the other hand, if one was playing a bass line on them with an actual upright bass patch or something, it would be nice to be able to accent notes. (Of course when operating it as a VPO console, the touch sensitivity on the pedals and manuals would all be disabled.) Y'all have any thoughts on this?

            I think it will be a pretty nice organ when/if the project is complete. The cabinet is really nice, anyway, which was the main reason I bought the thing (that and the pedalboard).
            Last edited by Mr. Polecat; 10-22-2018, 05:27 PM.
            1914 Estey Parlor Organ. 196x Allen T-12a "Special" (MIDI VPO project). Digital piano. Various guitars. Autoharp. Banjo. Bowed saw. Musical Cat.

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            • #7
              Actually, the pedal switches are pretty darn good. They are a standard pipe organ part, still used by many builders. I once used them for a MIDI project keying on 5v and they worked perfectly. They may need to be polished up, but they should be fine.

              If I were going to convert one of these to MIDI I'd probably just do away with the oscillators. While this simple and ingenious generator system was a great way to produce a variety of tones back in the 1950's when it was designed, the cheapest and simplest digital generator of today can run circles around it. It really isn't worth all the work it would take to key it with a bank of transistors and all that. Every shareware MIDI sound generator I know of can generate sine waves and mix them in unlimited combinations, and without all the quirks of these oscillators. (I would be advising differently if you were planning to restore and preserve an analog Allen entirely, as the larger ones actually DO sound very good and are much harder to mimic in software.)

              The Allen keyboards are better than you think. They do have wooden sticks with plastic end caps, and may well be worth saving. You could install some new keying strips with velocity sensing underneath the wooden keys. Many years ago, when cheap MIDI keyboards first became available, a tech I knew actually bought a low-end Casio or something and gutted it, using the key contact strip under an Allen keyboard to MIDI it. I've not done this myself, but it doesn't look like brain surgery.
              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

              Comment


              • #8
                Originally posted by Mr. Polecat View Post
                I am hoping that I can get jOrgan running on a Raspberry Pi 3 internally for synthesis, with a small USB touchscreen mounted somewhere
                jOrgan can certainly run very well on the Raspberry Pi 3, and one could argue that the two seem to have been made for each other! I have been deeply involved with jOrgan now for about ten years, and I am planning to run my home two-manuals and pedals console using two Pi3 B+'s with 7" touch screens, one mounted to the left of the manuals and one to the right.

                However, such use should still be regarded as somewhat experimental. I would advise you to keep an eye on the jOrgan Discussion Forum for threads devoted to the Raspberry Pi (I started a fairly recent one, but there are older threads as well), so that you can avoid all the work of having to reinvent the wheel.

                John Reimer

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                • #9
                  Originally posted by jbird604 View Post
                  ... a tech I knew actually bought a low-end Casio or something and gutted it, using the key contact strip under an Allen keyboard to MIDI it. I've not done this myself, but it doesn't look like brain surgery.
                  Hmmm, that's a pretty good idea. I was envisioning having to use a bunch of magnets and hall effect switches or reed switches to get a second switch under there (hence it being cheaper/easier in the long run to refit it with Keystation 61 manuals), but if a board of dome switches off a cheap electric keyboard will fit under there, and key right without making the organ feel spongey..... I think I have a broken electric keyboard in a pile... Somewhere.... Dunno if it's 61-key or not, hmm... But if that works then I'll need to find a second one, hmmmmmm..... It wasn't velocity sensitive, but I could use the existing whisker contacts for the other switch. Worth a shot.

                  One velocity sensitive manual might be enough anyway.

                  I have also thought about bending one of the whisker contacts on each key, so as to use it for the second switch for velocity-sensing, but I am not sure I can make the bends accurate enough to have consistency between the keys. If I could come up with a way to hit each key with the same velocity, I could probably write the software to calibrate to that and adjust for bent whisker inaccuracy... Maybe some sort of plunger with a spring behind it (nerf gun, maybe?), but... That would be annoying and complicated. Maybe some kind of whisker-bending jig, but I'll have to investigate that more...

                  Ugh, I am think-rambling as I type. Sorry!

                  I guess there's nothing stopping me from just wiring it up to the microcontrollers as-is, and then changing stuff around later, either. As long as I socket the microcontroller boards, I can just reuse them if I change things up, and I'll only be out of some perfboard, a few resistors, some wire, and a socket.

                  Yeah, maybe that's the ticket for the moment. Then I can play the thing as a VPO fairly soon, and add the fancy stuff later.

                  I guess that means finding a place for it with easy access to the back, though.

                  My cat also seems to enjoy crawling into the swell pedal hole and sleeping inside of it. I'll have to figure out some way to make it cat-proof, too..... Lol.

                  Originally posted by j reimer View Post
                  ... I am planning to run my home two-manuals and pedals console using two Pi3 B+'s with 7" touch screens, ...
                  Thanks! I'll check out your forums.

                  If I may ask, is there a particular reason you're using two Pis, rather than one Pi with two USB touchscreens hooked to it? Are you synthesizing the great and pedals on one and the swell on the other, for CPU-usage reasons, or something?
                  1914 Estey Parlor Organ. 196x Allen T-12a "Special" (MIDI VPO project). Digital piano. Various guitars. Autoharp. Banjo. Bowed saw. Musical Cat.

                  Comment


                  • #10
                    Hi Mr Polecat,

                    You mention embeddable re Hauptwerk assume because of H/W requiring a full blown computer (size wise)

                    An alternative to a Mac Mini size wise is a HP EliteDesk mini 800 G1 i5 4590T Quad Turbo 3.0GHz available with either Win 7 Pro or Win 10 Pro. Has 6 (built-in) - USB 3 ports. (2 on the front, 4 on the rear} This unit is actually smaller than a Mac Mini and can have up to 16 GB of RAM just like the M/Mini. Can mount horizontally or vertically. Quite a few appear on eBay (new or used quite reasonable). Only a single internal SSD or HDD. With a bluetooth adapter built-in except if you may not want battery mouse and keyboard but b/t saves on USB ports.

                    BTW, I use a small dot of various colored nail polish to color code the USB cables along with the associated USB ports because once you establish a USB device connection to a certain USB port you must not change that connection because H/W will look for that device on a specific USB port. (Nail polish remover if you need to make a change).

                    Rgds,
                    Ed

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                    • #11
                      Originally posted by Mr. Polecat View Post
                      My cat also seems to enjoy crawling into the swell pedal hole and sleeping inside of it. I'll have to figure out some way to make it cat-proof, too..... Lol.
                      Usually organ consoles need to be rodent proofed. I've opened many consoles with mouse fecal matter inside. So maybe your cat will prevent that.

                      Rgds,
                      Ed

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                      • #12
                        In my experience, mice, and what they leave behind, is better than what the cat does in there.

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                        • #13
                          Originally posted by Mr. Polecat View Post
                          If I may ask, is there a particular reason you're using two Pis, rather than one Pi with two USB touchscreens hooked to it? Are you synthesizing the great and pedals on one and the swell on the other, for CPU-usage reasons, or something?

                          Comment

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