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Baldwin 645C Organ MIDI Conversion

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  • Baldwin 645C Organ MIDI Conversion

    Hi All,

    I recently obtained a Baldwin 645C Organ which the previous owner gave away for free, since he was "unable to get any sound out of it". He had a couple of cabinet speakers which he attempted to hook up, and got sound briefly, but was unable to get anything more. He blew one of the speakers in the process of trying to hook them up, and decided to give the working one to a friend instead of passing it along with the organ. (I couldn't really complain about that, since I was already getting an organ for free...) My plan has been to convert the organ to a MIDI organ to use with Hauptwerk, but to repair the organ if it could possibly be repaired. I've tested the organ (what I was able to without speakers), and it appears it is somewhat glitchy with the stops, meaning that the lights on some stops will always be on and some will always be off no matter how many times you switch the stop on and off, and sometimes multiple stops will suddenly turn on or off when other stops are pressed. There hasn't been much more I could verify at this point, but obviously I'm wanting to move this forward so I can play it...

    I've done several internet searches, and have found that there isn't a whole lot online about the Baldwin 465C. I've read some topics on this forum about how this particular model is not an easy conversion to MIDI, how the soldering is oftentimes bad, etc. I've spent a decent amount of time familiarizing myself with the internals and am confident I can make the MIDI conversion, although I definitely see why it's not a straightforward conversion - they have a form of a scan matrix which is wired by the octave (12 keys) instead of the typical 8x8 matrix that MIDI encoders use. There is also a single bar connected along the length of the keyboard, which all switches appear to ground to. I still haven't figured out how exactly they're reading their key data, even after consulting with one of my friends who is a computer engineer. This would perhaps be possible to figure out, if I still had the organ wired up so I could throw a multimeter or oscilloscope on some of the contacts, but I've pulled the electronics out of the organ so I could access them and work on them. I will probably end up hooking things back up at some point, but that is going to take some doing.

    Anyhow, like I said, I'm confident I can make the MIDI conversion with this organ, and the easiest way to do it would be to completely gut the organ and alter the wiring of the keyboards. It would be fairly straightforward doing it that way, all I would need to do is cut the bus bars at 8 note intervals, find a way to support them where I cut them, then add a diode in series with the switch and hook up the MIDI encoder accordingly (I am using the hwce2x encoder from MIDI Boutique, by the way). If I do that, I would have no use for the electronics of the organ, and could (carefully) re-craft the organ console to make it a smaller size, just big enough to house a computer and any wiring needed for the MIDI encoder. This would be favorable in a way, because it's a heavy organ and was a bit of a pain to move, plus it's too big to move into my house and has to be taken apart to be moved in and out. Having a smaller console may be able to be moved in one piece, which would be nice, seeing as I'll be moving in a couple of years here. However, before I jump into an option like that, and not wanting to make a horrible mistake, I want to consider the possibility of keeping the organ internals and avoiding altering the wiring in the keyboards, so the organ could potentially be repaired in the future, should I choose to do so. There's a part of me that wants to keep that door open, though I definitely don't want to spend the money to have somebody come and repair it, and I don't want to spend the time myself right now to get repair manuals and figure out what repairs need to be made. I am a mechanical engineer by trade and have some electronics know-how, but the scale of the electronics on the inside are a bit overwhelming for me, so it is possible that it would never get repaired. But there's also the part of me that wonders if the organ has or may have historical value to where it is worth preserving the original electronics of the organ, even if I never get around to repairing it. If I do choose to preserve the internals and the wiring, I would connect to the one end of the switches and make a 64x1 scan row to 8x8 scan matrix conversion. Since I'm on a bit of a budget and since I'm in this for the adventure, I'm currently working on a design for that. If it doesn't work out, MIDI Boutique sells boards to make that conversion, which is my fall back option.

    Anyhow, my dilemma is whether I want to preserve the internals of the organ, which will make the MIDI conversion more difficult and somewhat more expensive, or if I want to gut the organ and convert it into purely a MIDI organ setup. The second option would allow me to cut down the size and weight of the organ, which will make it much easier to move. What are everybody's thoughts on this? I'm open for opinions and appreciate any suggestions.


  • #2
    The answer primarily depends on whether you like the sound of the original organ. If not, there's not much sense in going to the trouble of preserving it. Another factor to consider is whether there will ever be a time when you want to play and Hauptwerk will not be available, such as might be the case if your Hauptwerk computer is not dedicated to that function and is used by other members of the family.

    When I added MIDI to my Allen, I chose to keep the original electronics intact and playable; however, I can honestly say that since Hauptwerk sounds so much better, I've not once had the desire to play the original.

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


    • #3
      Thanks for the comment. At this point I don't know how the original organ sounds, but I'm hesitant to alter the electronics in a way that would prevent me from ever repairing the organ, if I would choose to. Currently I'm working on some digital circuitry that would enable me to read the keyboards with my MIDI encoder with no significant alteration to the electronics, I'm hoping this works out. If it doesn't, then it's an obvious choice to gut the organ and convert it solely to a Hauptwerk organ.

      Also, I was wondering if anybody else has a Baldwin 645C that happens to have sound samples online that they could point me to? I would like to hear what the organ sounds like to help me in my decision, particularly because I won't be getting sound out of it anytime soon. I just want to have some idea if it's worth it or not.



      • #4
        I don't have any sound files, but I have serviced and played on a number of 645's and related models, such as the 635, 626, 632, and 636. The sound might be described as rather good for analog but certainly not comparable to digital as far as pipe realism.

        Just to open, I'd say that the problems you describe with the stop action not working correctly probably indicate that the CPU stack has problems and might even need replacing. A third-party CPU board for this organ was once manufactured after Baldwin quit supporting it, but that is surely long out of production now. So you may not even want to read the rest of this post, as I attempt to describe how it works and sounds, because without a working CPU system, there isn't anything about the organ that is going to work properly. It's just a shell with nice keys and pedals that is begging to be gutted and used for a VPO console!

        The 645 and other models with the same technology from Baldwin had a very effective and unique-to-Baldwin system called "rate scaling" that allowed the organ to generate several complete sets of pitches, all of them derived from just one master oscillator but slightly offset in tuning. This gave it the "ensemble" quality or "random detuning" character otherwise associated only with large analog systems using multiple ranks of oscillators, without the need to tune several hundred individual oscillators on a regular basis. For example, one octave of the 8' Principal stop might be tuned dead-on at A440, then the octave above might be a couple cents flat or sharp of A440, and the octave below might be yet another couple cents sharp or flat. And a complete rank of celeste pitches would also be derived from that single master clock, giving a set of tones about 8 or 10 cents sharper than A440, for a just-right celeste.

        Combining numerous stops at different pitch levels, you'd get the "shimmering" quality of a large pipe organ that was very slightly out of tune. This added to the illusion of pipe sound by avoiding the sterile lock-step tuning that we so often associate with ordinary analog organs, especially single-master-oscillator systems. The use of a single master oscillator allowed them to have a full-range transposer, and made it very easy to quickly tune the whole organ up or down by a few cents if necessary to match an errant piano or orchestra.

        The tone colors were all derived from these several ranks, first by using different types of multiplexed diode gate boards to pass the square waves (thus converting some of them to pulse or sawtooth or other shape, preparatory to filtering them to suggest the desired stops. Standard analog ladder filters were then employed to finish off the various stops and ranks with a rather good simulation of the right tone color for each stop.

        A set of chiff gates provided a decent analog attack sound on flutes. Anyway, all this doesn't really tell the story about how it sounds. It sounds pleasant, but if I have a criticism it is that the pitches are so rock-steady (no intentional "jitter" is applied, and no "white noise" is injected to simulate air sound, as many other analog builders did) that they sound artificial, even though the tone colors are actually quite "right." The reed sounds are intriguing and interesting, flutes just hollow enough, principals bold and sturdy, mixtures clean and brilliant. Just somehow not very "real."

        Honestly, it can be very time-consuming and costly to fully restore one of these monster organs to good order, especially if you need a CPU board, or if there are a number of bad gate chips or other components to be replaced. These days, it probably makes more sense to sink your time and money into converting it to MIDI and playing much more authentic sounds via the VPO route.

        No historic value or interest, just another old analog organ that was technologically obsolete before it was even built, as Allen had long since given the world digital organ sound, and the difference was obvious to anyone. Many of these have gone to the landfill, so at least you'd be saving the console and the re-usable hardware.
        *** 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
          Thanks for your reply! That definitely helps, and I think I'm more set on just gutting it now and moving forward with the MIDI conversion. It will be a much cleaner setup, and I'm also realizing that I'm not very motivated to put all the electronics back together. It is a bit of a mess on the inside, and it's true that I'm apprehensive hearing how these models typically have issues with bad soldering and with the knowledge that the previous owner was unable to get any sound out of the organ (and also blew a speaker in the process, though that could have been from incorrectly hooking up the speaker). Also, if you're saying it likely has issues with the CPU stack, which I kind of suspected, I'm thinking it may not be worth my time or money. After all, I'm planning to put some money into a dedicated computer specially built to run Hauptwerk when finances permit. Aside from that, I appreciate the detailed explanation of the sound generation in the organ, even if I don't stick with the original organ, I find it very interesting. It does sound a bit dated and defunct, however, not like a classic instrument that is worth spending the time and money restoring. I just didn't want to make a mistake in case it was, though...

          While I'm at it, does anybody have any experience and any opinions on the Major I (American Classical Organ) or the Major II (Northern European Cathedral Organ) sample sets from Etcetera Pipe Organs? When I do get Hauptwerk up and running, I'm thinking I want an organ that closely matches my console (3 manuals with AGO pedalboard and about 65-75 stops, I would have to count exactly). These sample sets are attractive to me because they seem to be reasonably priced and have both wet and dry sample sets which come with it. I would likely practice with the dry sample sets, because in my opinion it helps to weed out bad technique, but play with the wet sample sets when I'm playing for fun. I've listened to the samples of both organs online, and in spite of the positive aspects that I've listed, I'm a bit leery of sample sets that are taken from multiple organs, as opposed to sample sets taken from a single organ. I'm not sure if the acoustics would match up entirely because of this, and don't know if anybody with more experience and a better ear would be able to shed some light on this. Once again, any suggestions are appreciated.