Allen Gyros, Whind, Trems and other fun analog era stuff

[AllenAnalog]

Gyro Gearloose is stepping in for Larry for this message. Any admissions of obsessiveness made by GG may be denied by Larry.

Instead of further hijacking Lamar's (Silken Path) epic TC-4 thread I'm posting a new thread in this same forum (rather than the Leslie, Tone Cabinet Forum) because it is connected to the current discussion.

I became fascinated by Allen Gyrophonic Projectors when I was in high school. The school auditorium had a 500-tube Allen organ with four commercial-size (I'm guessing the rotating disks were at least 36" diameter) Gyros in a 2x2 stack on top of the twelve 15" pedal speakers. The first time I saw them in action they were in the very slow rotation mode for random motion. I was mesmerized.

Allen made an incredible number of variations of speakers, amps, auxiliary devices and stationary/rotating layouts inside the same furniture style cabinets for the TC-x and theater organs of the 1960s. My 1971 3-manual analog theater organ came with two Gyro cabinets having the larger 29" rotating disks. The string cabinet has a DC motor and multi-speed controller with the selenium rectifiers but only two of the three speeds are used.

The flute cabinet has an AC motor - on/off only. There are two speakers on the disk but one is for balance only, not connected. (Curious design concept #1.) There is another speaker cabinet for the pedal, traps and upward firing cone speakers for a non-tremulated flute channel. There are both Vibrato and Tremulant tabs. One of them (I forget which now) runs both the rotating and stationary speakers at the same time. (Curious design concept #2.)

The reed channel speaks through upward-firing cone speakers on the flute cabinet; there are no horns. The combination Whind/Tremolo chassis was used to put an electronic tremulant on the reed channel generators only. It was disconnected when I bought the organ, as was the Whind circuitry.

Continuing my high school fascination with all things relating to rotating Allen speakers, I bought four Allen speaker cabinets on ebay that matched the furniture style of my existing cabinets. I picked them up in Cleveland on my way home from a visit to family on the east coast. There are three medium and one short height cabinet, whereas the three cabinets that came with my theater organ are what I call the tall (34") cabinets.

I bought them because one of the cabinets had the upward firing Jensen horns that I coveted (but no motorized flappers). Two cabinets had rotating disks but they are smaller than the ones on my theater organ. Then I found a couple of the 29" Gyro disks with three woofers and three tweeters on each disk. They had been in the annual Allen factory surplus sale and were purchased by locals and then listed on ebay. They were brand new and unused. All three woofers are connected in a series-parallel circuit with a power resistor substituting for the missing 4th driver to keep the levels balanced between the three woofers.

My thought was to convert my third tall cabinet to another gyro cabinet for the reed channel, with both the Jensen horns and a rotating disk. And also upgrade the string cabinet disk. But with Lamar's comment that he did not like the sound of the reeds in a rotating speaker, I'm not sure about that now. And then there's the question of why there is only one connected driver on my flute disk. How will having three spinning woofers sound in comparison.

I like the idea of the multiple speeds for the Gyros. Slow for random motion, slightly faster for celeste and faster for tremolo. I do have three of those horribly obsolete selenium rectifier DC motor drives! Doing some online research I found some fairly inexpensive solid-state fractional-horsepower DC motor drive PC boards. I think they will work but I need to be sure they do not create high frequency electrical noise that will get into the audio through EM radiation out of the motor wiring and windings.

Ah, the joys of infatuation with obsolete technology. Yes, I'm delighted with my Hauptwerk experiments. It sure is a lot easier. And I have no doubt that all of this will end up at the recycling center when I'm gone. But I do still love the sound of an analog instrument.

Despite being two months behind on my move due to multiple complications from hernia surgery, one of these days I'll get around to my projects.

[SchnarrHorn]

Could you post something about your 500 tube Allen, or, if you had done so in the past, a link to said post?

[AllenAnalog]

I edited my original post to make it clear that the Allen organ I mentioned was in my high school auditorium, not my home. Sorry for any confusion.

Trenton (NJ) Central High School was a mammoth building, built in 1931. Despite the Great Depression, no expense was spared in its construction. It was 4 city blocks long and there were 4,000+ students when I was there. After WW2, students sold candy to raise the money to buy an organ for the auditorium, which seated 1,500. It had six large chandeliers with over 250 Lenox china bowls on the lights. There were dual 35mm projectors in the projection booth and a massive fly gallery over the stage.

It was a 2-manual instrument, model W-5S, serial number 215, built in 1947. I don't know how much the organ cost but some 1946 documents offered on ebay a while back showed a stock W-4 organ price of $5,445 - a lot of money in that post-war era. I'm not sure what stops and features the W-5 model added but I assume the "S" was a custom version of the standard W-5 model. It cost $300 more for the walnut cabinets to cover the tone generators.

There were four large cabinets with multiple chassis inside filled with 6SN7 vacuum tube oscillators and a rack of McIntosh tube power amplifiers. The console was in an angled loft to the left of the proscenium opening, about the height of the front of the balcony.

The speaker array was in a similar loft to the right of the proscenium. A battery of ten "echo" antiphonal speakers was mounted at the base of the projection booth at the top of the balcony. There was a small auxiliary keyboard for the Maas-Rowe chimes.

It was a grand sounding instrument and every time I played it I was inspired. So different from the Hammond spinet we had at home. Of course that huge room also played a role in the impact of the sound. I remember being particularly impressed with the 16' Tuba on the pedal.

During the years 1962-65 that I played it an Allen tech came down from the factory twice a year to tune it and fix any problems. I remember reporting a couple of sour notes and some static from the slip rings on the Gyros but not much else went wrong with it during my time playing it.

Living just a half block away I was fortunate to walk to school around 7 AM a couple of days each week (when the cleaning crews were there) to practice before classes started. An understanding principal let me come in during the summer to practice.

I only played it once in public - for a gathering of 1,200 teachers in the area. Otherwise it was just the cleaning ladies who were my audience. I didn't even realize were in the balcony until they applauded one day. One of the teachers in the commercial department played the organ for assemblies since none of the music teachers knew how to play organ.

Sadly, in a move that still baffles me today, the State of NJ decided to tear down this magnificent building a few years ago. The organ loft had been broken into and the instrument was vandalized and rendered unplayable some time in the late 1970s.

The attached image is a scan of a Polaroid photo I took about 1965 before I went to college. For some reason the photo editor will not allow me to show the W-4 document beyond a thumbnail.

[SchnarrHorn]

Very interesting! Thanks for posting. I really like the detail on the music rack - no simple rectangular slab!!

Yes, a lot of money, but tubes with point to point wiring, in general, was always very expensive to make.

George

[toodles]

If you click on the tumbnail it gets bigger--and then click on the image, and you can read it clearly.

Seems this is a lot like the early Conn organs and Artisans--a rank of 8 ft. generators per division and then filters to change voices. Different pitches were achieved via coupling. The Allen, though, had a celeste rank, and the voices were probably more refined than Conn/Artisan, and more pitch couplers than Conn/Artisan, too. Thank you for sharing.

[AllenAnalog]

Yes, for some reason the photo anomaly seemed to resolve itself after I logged out.

The celeste rank added an amazing warmth to the sound. Since all of those oscillators were never perfectly in tune, the organ had a warm, rich sound to begin with. The impression that sound made on me when I was 16-18 years old probably explains why I still cling to my Allen analog theater organ, despite owning 3 digital instruments and having MIDI to drive Hauptwerk on two of them.

Other memories of that instrument came back to me this morning.

The heavy "thunk" sound of a massive electrical contactor (relay) closing when you turned on the console power switch.

The large cables underfoot as you walked between the console and the tone generator cabinets.

The eerie blue-green glow of the mercury vapor rectifier tube inside the console that provided the DC power for the four large Gyro motors was a bit of a shock to me when I opened the console lid to look inside.

The various size steel washers taped to the tops of the chassis above the fixed tuning inductors to fine tune a note when the selected capacitor (attached to screw terminals for easy replacement) for that note did not bring it into perfect tune or had drifted a bit.

[hp_lovecraft]

That Allen Gyrophonic Projector is pretty cool.
Our church had an old 60s Wurlitzer in its chapel that had a Spectratone cabinet that worked kinda similar. In that, they both have spinning speakers, not cones like the Leslie.

It made a really hauntingly beautiful sound..... until the belt would break. lol

[Silken Path]

I'm interested in how the "soft start" or "ramp up" feature of the DC controller works. I wonder if one could stop it at one of the intermediate steps and get another speed out it.

But this is pretty arcane. I should be worrying about getting rid of the selenium rectifier. I brushed against it and got a shock.

[AllenAnalog]

The Allen schematic for the DC Gyro motor controller shows single diode, half-wave rectification of the field coil voltage and full-wave rectification for the armature. It lists two modern substitutes for those units.

The CR19 substitute is a Motorola MR506 600-Volt, 3-Amp diode. CR20-23, the big selenium bridge rectifier, can be replaced with a Motorola MDA-3502 solid-state bridge rectifier or equivalent. The MDA-3502 is a 35-Amp unit in the usual potted square format with four push-on terminals. It would mount to the chassis (as a heat sink) with a single screw through the middle.

Allen used different brands and HP ratings for the DC motors in the Gyros over the years. I have seen 1/15 HP and 1/12 HP units. So that 35-Amp rating is certainly plenty for those motors.

Given that the transformer has 8 taps and the two relays (on most models of this chassis) are wired to three of them, with control of both relays you can get three speeds and off. Not all organs gave access to all three speeds. What they call ON or Normal I consider to be the "random motion" speed since it is the slowest. The "Celeste" speed is between the Normal and Tremolo speeds. The tremolo speed has an adjustable resistor to change the speed.

See the schematic for most models below. There are some much older units that are not wired the same. Those are the ones with the screw-in glass fuse on the side of the chassis.