Good point. I guess if I were to tighten up the spacing of the individual generators within the rack, then it might be possible to do.
But I'm confused now. ... So does this mean on a TC-4 the corresponding flute *doesn't* sound along with the reed voice, as it does on a TC-3 (and on a T15 for that matter, I suppose TC-1 also).
...
"Each tonal family, produced by a separate source, retains its own characteristic attack which serves to enhance the superb full organ ensemble." Does that mean the TC-4's separate reed circuits also have a provision for a different ADSR envelope? Or is this just marketing-speak for "on this one the reeds can sound without the flutes tagging along"?!?
Well, this is all highly interesting to me anyway... :-)
1. Note that the TC4 reed oscillators had ONE FILTER PER NOTE; this is note-by-note voicing capability. I don't think the "flute trunk" did that (to me "trunk" = "bus" and that means all note outputs consolidated); I think it was a lumped filter (but I don't have my schematics in front of me). Even if the flute trunk approach did note by note filtering, as far as registration, you would get the reed along with the flute for every flute and reed pitch level selected, and that is very much different than flutes at specific pitches and reeds at others.
2. Yes, the keying envelope would likely be different between flutes, principal, and reed ranks. The reeds would have a faster attack than the flutes.
Yes, adding a separate reed rank would be valuable. It would give a bigger ensemble and allow indepenent selection of flute, principal, and reed pitches.
Good point. I guess if I were to tighten up the spacing of the individual generators within the rack, then it might be possible to do.
But I'm confused now. If the reed voices on a TC-4 were derived by taking the notes from a flute (sine wave) generator and running it through Allen's "tone changer", i.e. the clipping diode circuit mentioned before... then how much of a difference is that over the TC-3? --Since again, the TC-3 already does the same thing. It sounds like the main difference is that in the TC-4, the tone-changer/reed section has a flute generator all to itself, so to speak, whereas on a TC-3 it has to share the flute generator with the flutes themselves. So does this mean on a TC-4 the corresponding flute *doesn't* sound along with the reed voice, as it does on a TC-3 (and on a T15 for that matter, I suppose TC-1 also). If that's the only difference then it may not be worth all the work to add another generator.
On the other hand, the old Allen brochure someone was kind enough to share on here says the following about the TC-4:
"Each tonal family, produced by a separate source, retains its own characteristic attack which serves to enhance the superb full organ ensemble." Does that mean the TC-4's separate reed circuits also have a provision for a different ADSR envelope? Or is this just marketing-speak for "on this one the reeds can sound without the flutes tagging along"?!?
Well, this is all highly interesting to me anyway... :-)
Either way you're right: space may be an issue anyway. I hadn't really gotten in there to look; I was still just at the speculative "I wonder if it would be possible to..." stage. But I pushed the TC3 out today for a look: darn! There's considerable empty space, but not such that I can see any way to fit another generator rack in there. The space just isn't configured right. So the only way might be to go with external generators... rats.
Anyway I appreciate the lively discussion!
You might have to move the existing middle set of oscillators up or down some, but space can be found for the additional set of oscillators, as the TC4 used the same console, and had the additional set of oscillators.
It is feasible to add an additional rank to an Allen analog organ--if there is physical space for it. The reed ranks used the basic sine wave oscillator (same as the flute), passed it through a diode to rectify it and add harmonics, then had a filter for each note.
Interesting... this is precisely what happens in the reed "trunk" on the T15 etc. Allen called this diode circuitry a "tone changer". I guess I assumed the reed generators per se (i.e., on a TC-4) might've been done differently, by generating a square wave or sawtooth wave or something, then filtering it down. ...So it sounds now like this would be possible to do, but would require essentially sacrificing a T15's entire tone generation system.
Either way you're right: space may be an issue anyway. I hadn't really gotten in there to look; I was still just at the speculative "I wonder if it would be possible to..." stage. But I pushed the TC3 out today for a look: darn! There's considerable empty space, but not such that I can see any way to fit another generator rack in there. The space just isn't configured right. So the only way might be to go with external generators... rats.
The bottom (16') octave of the flute and diapason was shared on the TC 6. This is likely true of the TC 4 and TC 5. At some point a 32' Contra Diapason became standard on TC 4/Classic, TC 5, and TC 6.
Apologies for "bump"-ing this thread back to the top, but... here's the kind of thing I'm considering:
Don't apologize. We discuss old Allen organs! It's what we do!
Good luck with your project. Keep us updated if you decide to go this route. I would wonder if a generator board from a T12 can fill the shoes of a >= TC3 board. For example, I'm not sure but did the TC3 have a 32' pedal flue? In that case the T12 might not be able to go low enough. IIRC someone once said that the diapason and flute ranks in the TC organs share the lowest 16' notes right? So maybe it wouldn't matter if the diapason rank is where the pedal notes originate. (edit: it doesn't have a 32' stop. Did any "standard" TC organ have 32' stops?)
It is feasible to add an additional rank to an Allen analog organ--if there is physical space for it. The reed ranks used the basic sine wave oscillator (same as the flute), passed it through a diode to rectify it and add harmonics, then had a filter for each note. Generic schematics are in "Electronic Organs" by Norman Crowhurst Vol. 2 for the Model 314--basically a TC4 stretched to 3 manuals; the model, 314, came from the number of oscillators I was told.
I know I would not enjoy the wiring nightmare of doing this, but it is possible.
If you decide to buy the generators on ebay, as they are already flute generators, you would want to use the exciting flute-reed generators in your TC3 for reeds only. I do not know what is involved in this, but I am sure others can answer the questions you may have.
I myself had considered a project like this some years ago, when I had a TC4, to make the manuals independent by adding generators from a TC3 or 4 for the Great manual and Pedals, and sometimes wish I had gone ahead with the project. The Allen analog tone generating system sounded a whole lot better than anything digital at that point, and i think that that only Hauptwerk beats it today.
Upon further investigation, my TC3 definitely has three "ranks": flutes, diapasons, and celeste, with the reed "trunk" drawing off the flute generators. So this leads to two shortcomings, both mentioned before: 1) the corresponding flute tone always sounds along with the reed tone; 2) if you have a stop like "Trumpet" selected, adding other stops makes little difference in the timbre, since "Trumpet" is already calling on so many of the available tonal resources. (for the record, mine doesn't have any green-colored tabs; I think those must've been on the Theater models - ?)
So anyway my thought was just that it might be possible to add a spare rank of generators, such as the one on Ebay, as a dedicated tonal resource for the reed voices. At the very least, this would minimize problem #2 above. But really I was hoping that the additional rank could be reconfigured as identical to the reed rank in a TC-4. So I guess my main question is whether the oscillators themselves would differ, i.e. between a tray of Flute generators and a tray of Reed generators? --I haven't received my technical information packet from Allen yet, to get a peek at the schematics, but intuitively I would think the design would have to be different. So maybe this is a red herring after all...
In any case I appreciate the discussion and additional info... and Nullogik, I too would love to see the scans of the TC4 and TC5 brochures, if you come across them.
Nullo, did you scan those brochures? If you did, great! I'd never noticed the organ brochure gallery on this site. I love how the brochure for one of the smaller MDC organs says it "looks like an organ, sounds like an organ, and plays like an organ". LOL. What's the matter Allen, have something to hide? Those instruments were dogs! "The MDC tone generation is in a class by itself" - yes, arguably, the worst Allen ever had.
I've uploaded a scanned copy of the Allen TC-3 brochure. Click below for the first page and then use the single blue arrow pointing right to move to the next three pages.
Somewhere I have TC-4 and TC5 brochures/stoplists. I can scan them and upload them if anyone wants them.
Toasterdude, if you want to do serious mods to your TC-3 then I suggest the Allen Technical Service Information Pack for the TC models is worth getting. I think it was only about $50 (it was a few years back that I got mine) and there are plenty of schematics and circuit diagrams. Definitely money well spent.
Toaster, I'm not a serious enough electronics hobbyist to comment on mods; but I own a later analogue Custom Carousel and it has a very serious trumpet stop. I'm sure this was accomplished by filtering so I would raise the possibility of an easier route to a reedy organ would be found on your voicing boards. With two large gyros I'm certain you have enough "chorus" to hide the missing rank.
Thanks Mark, good to know you are still around. I think I was confused by the "Some voices appeared at a reduced volume, accomplished with resistors" a feature you'd discussed early in relation to the >TC5 organs. I'd just assumed it required diode keying to do something like that. Thanks for clearing it up! I think the Cedar Lane Unitarian custom 2 manual that kicked around the DC area in the used market had that Harmonic Trumpet/Bombarde rank...the badly recorded but stirring Mp3 file of one of the organ's last church performances had an incredible trumpet sound.
Sound like the "trunking" appeared in the TC3! That might explain why I'd once thought those had a separate reed rank. I assume all TC organs had "diapasons become dulciana"?
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