My "New" Rodgers 580 organ project!

[jbird604]

Finally brought home the Rodgers 580 "Cheetah" organ, that I recently got for free, to be my next home organ project. No longer organ-less, I think I'll sleep better tonight. At least I'm more content with an organ in the house :-)

It was dead when I got it, but with some TLC and a pc board from another scrapped-out Cheetah it's back to 100%. The internal speakers had been robbed, including the 3-way crossover, so I took the opportunity to create an audio system to my liking from scratch.

The Cheetah digital system consists of (1) a single DVM (Digital voice module) tone generator board, as used in the PDI cage of larger organs, though larger organs have several of these in the cage. (2) An interface board that connects this DVM to the stops, expression pedals, keys/pedals, pistons, and other console controls, and handles MIDI signals. (3) An audio processor board that receives the output of the DVM, contains the bass/treble/level pots for each channel, mixes the four signals down to two for the smaller models, sends and receives the reverb audio, sends and receives the AUX and headphone signals, does turn-on/turn-off muting, and sends audio on to the power amps. (4) The usual peripherals, such as power supplies, jack boards, stop rails, reverb board, and so on.

Whether the final audio mix is two channels or four depends only on a pair of jumpers on the audio board, so I clipped out the mixing jumpers and made it four channels. For better control of the great/pedal division, I "biamped" those two channels with a stereo amp handling the bass and another stereo amp handling the treble. The swell channels are wired to a third stereo amp, for a total of six channels. Here are the speakers I used:

The great/pedal bass is fed to a pair of 12" woofers mounted in the kneeboard where the original speakers had been. In order to make the kneeboard mostly "air-tight" and maximize bass output, I sealed over the holes where the mids and tweeters had been, as well as some slots that Rodgers left open for cable drops, and I sealed around the expression pedals too. The back of the console is partly fabric, and thus vents the bass out the rear, but by eliminating air leaks in the front I hoped to decrease front/back speaker wave interaction and extend the bass response downward, improving the fundamental of the 16' stops. I also hoped the rubber-surround woofers I used would produce credible output down to 32 Hz as required for these tones. I believe my work paid off, as I'm hearing very full deep bass, all you could want from 16' stops. These speakers are so efficient in the lowest octaves that I had to turn the bass controls on the audio board down a bit from the marked factory position.

The gt/ped mids and highs go to my modified "pipe" speaker. Originally a single-channel Conn model 145, I converted it to stereo by removing the four 6x9's and putting in two 6" closed-back midranges and two horn tweeters. With the pipes powered by a separate amp I can regulate their volume and tone as needed to match them to the low-frequency system.

The two swell channels play through the "Makin" system I used with my old Allen and with the Viscount. It consists of a pair of 10" woofers in a box in the floor and a pair of mid/high satellites with two 6" speakers and a dome tweeter in each one. The satellites are on a shelf 5' off the floor on the wall opposite the console, with drivers facing up at the ceiling.

So, sitting on the organ bench, I have the bass coming out at my feet, the great/pedal trebles coming from the "pipes" atop the console, and the swell coming from behind me. It's nice to have a divided organ like at church. There's a headphone jack for practicing when others in the house grow weary of my playing ;-) but it sure is a lot more fun to hear it through the speakers. The built-in digital reverb is quite good at simulating a large lively church setting.

Overall, the organ performs better than it should, considering its lowly position in the 90's Rodgers product line. As I've mentioned before, the Viscount unexpectedly and unaccountably spoiled me with a realism and presence that I don't quite hear in many small digitals. But just the bit of playing I've done today has relieved some of my doubt, and I think I'm going to warm up to this little thing. Some of these stops are truly lovely.

The keys and tabs feel a little flimsy compared to the Viscount's, but it does have a great pedalboard, like all genuine Rodgers consoles built in Hillsboro. The gorgeous chimes on the Viscount far outshone the odd-sounding chimes on this 580 (and all PDI Rodgers organs, for that matter), but many other stops are in fact quite realistic, just different from the Allen stops I am used to, and more processed than the Viscount tones.

The stoplist is closer to the MDS-45 Allen's than the Viscount's was. It has a Flute Celeste on the great, and a Cromorne too, two stops I really missed when playing the the Viscount. With only 29 stops, the pedal is sparse but good enough for the playing I do. There's nothing really vital on the MDS-45 that's missing from this stoplist, though of course I'd have loved a 32' pedal stop at home ;-)

Surprisingly, the celeste works almost like "celeste tuning" on a doubled MOS Allen. Drawing the celeste stop shifts just the left or right channel of certain other stops in the same division sharp, and they become "celestes" too. I haven't fully explored this quirk, but it seems to make for some interesting possibilities in celestes, which I dearly love.

Perhaps I'll eventually own a bigger home organ with more audio channels and fewer compromises. But on a "semi-retired" income "you can't always get what you want." But this is the organ I need right now and I'm certainly grateful for it. There are many folks who play far better than I do who make do with less of a practice organ.

CONSOLE PICS -- the five pics in this post. (Other pics will follow in subsequent posts.)

The 580 console set in place with the pipes on top, the two external amps visible. (The woofers are driven by the organ's internal amps.)

Closeup of the "voicing" section of the audio board showing volume (orange), bass (red), and treble (yellow) pots for each of the four channels. This is the extent of the voicing control for this model, but it seems sufficient.

A view from the rear with the back off, before mounting the woofers. Shows the kneeboard sealed up, with cardboard stapled over the mid and tweeter holes and the cable slots, and a cardboard "boot" attached to the expression pedal housing. The 2.5 mH coils are visible just below the woofer holes, ready to be wired in series with the woofers for a 500 Hz roll-off.

Two-page original Rodgers brochure showing console, stop list, specs, etc.

[jbird604]

GREAT/PEDAL SPEAKERS

The pair of 12" rubber-surround woofers before installation in the kneeboard

The speakers inside the "pipe" unit -- two 6" mids and two horn tweeters. The red cardboard "wings" around the mids are there to gather up any sound that might otherwise be lost in the box and re-direct it out the pipes. (I'm superstitious about speaker efficiency, I know.)

SWELL SPEAKERS

One of the two Makin satellites, cover removed, with its two 6" and one dome tweeter, used for the treble of the Swell. These satellites are actually full-range speakers in their own right, but crossed over from the 10" woofers at 400 Hz.

The two 10" Makin woofers of the Swell system. Each woofer has a 3.2 mH coil in series for a 400 Hz roll-off point. (coils are inside the box)

[Darth-Car]

What a great new treasure you have there, and it fits in that corner perfectly. (You knew you needed something for that corner.):-)

We Rodgers guys have to stick together.

[jbird604]

Well, thank, Admiral! Yes, it fits the corner nicely. Not shown is the upright piano that has to back right up to it once I get everything tidied up in the corner. Pretty snug when I'm in there practicing!

I trust your Rodgers project will be every bit as exciting, so don't fail to post some pics of it too.

[myorgan]

John,

You couldn't have a more perfect fit! Now you and your wife can practice piano/organ duets for church. I'll bet you miss the toe studs after a while.;-)

Enjoy your new instrument, and as always, we can't wait for the recordings!

Michael

[jbird604]

I do miss the toe studs. Used to hang my slippers on them, never could get the hang of using them as pistons ;-)

[Silken Path]

It's purty, John...

[rjsilva]

It's nice to read about your project and see the photos, and glad you have a home organ again! Looking forward to possibly hearing a recording of it...

[jbird604]

Thanks, Lamar. Ain't too bad for a country boy's!

As I play around with it tonight, I'm discovering how Rodgers did some of their tricks, and surprised at how similar some of the concepts are to Allen (and probably other organs of the same era).

For example, the Great division seems to have exactly two pitch tables, with the stops more or less evenly divided between them, as in ADC and MDS organs. So drawing the 8' principal and the 8' primary flute, you get some beating. The 4' flute matches pitch with the 8' principal, and vice versa. And so on up the registers in fairly predictable manner. The 8' principal matches pitch with the Flute Dolce but not with the Rohrflote, a fact that yields a surprising consequence...

Now, follow me here, since Rodgers samples are "stereo" (PDI), each stop is really two ranks, one "left" and one "right" -- almost exactly identical, but with some subtle differences in tone color, supposedly due to the different microphone positions when sampling. (uh-huh) Under normal playing conditions, these two "ranks" that make up each stop are tuned dead-on, referencing the same pitch table. One is heard through the left channel, one through the right, at equal levels.

The manner in which the pitches are handled is altered drastically when the celeste stop is drawn. The stop that is the basis for the celeste (which is the Flute Dolce on the great and the Viola on the swell), gets its two ranks detuned by an amount that creates a celeste. So the great flute celeste is simply the Flute Dolce stop with one side tuned sharp. Since the 8' principal shares the same pitch table as that stop, the principal is affected by the celeste tuning, as is true of the 4' flute stop. That means that the two "ranks" making up the principal stop become detuned and turn into a "principal celeste." The rest of the great stops, such as the 8' Rohrflote, the principal upperwork and mixture, the Cromorne, etc., are not affected.

I've discovered that a similar action takes place on the swell manual when the Viola Celeste is drawn. However there seem to be only a couple of other swell stops that share the Viola's pitch table, and they are two of the reeds. So you get an Hautbois Celeste, and that is not a useful stop!

The pedal division also has two pitch tables but they are only very subtly separated, so there isn't much beating going on. You can hear an ever so slight wave when both 16' stops are drawn since they have different pitch tables.

In Allen organs, at least up through the early MDS models, stops that share a pitch table also share an audio channel, and there are no stops in the same audio channel that refer to different pitch tables. So the outphasing and aliasing are minimized, though there can be some of it due to the octave to octave offsets. But in this Rodgers, incoherent pitches are funneled together in the same pair of channels for each division without too many side effects. Not sure how they managed that, but it seems to work well.

Anyway, I'm having fun. Just spent a couple hours practicing, and man am I ever rusty! Must get many hours of practice in before Sunday morning!

[jbird604]

Not complaining (yet), but I do have to wonder .... On most of the non-Rodgers lighted-tab organs that I service, including a great many Johannus, Galanti, Viscount/Baldwin, Content, etc., I almost never have to replace a tab lamp. But the tab lamps are already dropping like flies on this Rodgers. I replaced a half dozen that were out when I got it, had two or three others go out while it was being repaired and tested in the shop, then when I got it home there was another one out.

Fortunately, the lamps aren't soldered in, just a twist-in-place "neo-wedge" type, but you do have to take the back off the organ, and for some of them a small pc board has to be removed to gain access. So it's a pain for sure in my cramped little music space. Would've simplified things if the top lid of the console were hinged, but it isn't.

Sure hope this isn't going to be a constant problem. Also thinking of some kind of long-term solution, perhaps a way to lower the voltage going into those lamps. (this organ doesn't have a lamp brightness control, as many Rodgers organs do) They are certainly brighter than they have to be, and maybe they'd last longer if the voltage was cut by a volt or two.

[rjsilva]

Are they moving tabs or are the lights necessary to see that they're selected? Just thinking that maybe you could take them all out :)

[jbird604]

Not moving, need lamps, otherwise no indication that the stop is on. I've seen LED replacements, might do that eventually.

[ctthayer]

I had a Rodgers 730 years ago, and those little twist-in tab lamps could get annoying. Fortunately, I never had to buy a replacement bulb, just had to lift the lid and reseat them. At first I found it tough to locate the while looking down from above, until I learned to leave the organ on and activate the tabs on either side of the dark one. It was still a pain, removing stuff from the top of the organ, standing on the pedals (!) and holding the lid up with my head while I reached in and did the job. I think it's Rodgers' method of seating those things that's the issue -- they seem to loosen themselves. But maybe an LED replacement project is the way to go.

[jbird604]

Thanks for the comments, ctt. In servicing this type of Rodgers, I've sometimes found the lamps to be loose and they'd come alive with a little twist. The ones I've had to replace here have been genuinely burned out though, burned black inside the glass in fact. But some of them may have been in the organ for 20+ years, so perhaps they will last longer than I think.

After another couple hours playing today, I'm ready to say that I like this organ and I'll probably keep it for the foreseeable future, barring the appearance of something extraordinary. There are things I'd change if I had my druthers, but it really does have quite an agreeable sound. I'll try to make a recording that will give a good representation of the sound and put it up for audition here soon. There are some fascinating things going on in this little machine.

Trying to listen critically, I keep feeling that some stops, particularly the primary 8' stops, lack "body" or something, that they sound a bit thin or weak. If there were midrange controls on the audio board, I'd be inclined to boost it a little. I'm wondering if I need to add some upper bass/lower midrange speakers to lend it some weight without making it tubby. I just don't know exactly what is missing, but when I have time I'll do some experimenting.

With the Viscount, the individual stops were of great beauty and detail but the ensemble was somewhat thick and indistinct. With this Rodgers, while the individual stops may be less appealing, the ensemble is very nice. Piling on stops, I notice that it remains clear and vibrant. So maybe the "thin" quality of certain stops is something that must be accepted in order to have a pleasant ensemble.

There are still some details to attend to. There is a rather annoying mechanical hum transmitted into the console from the large main power transformer. Next time I have it open, I'll try putting some kind of isolating material between it and the wood. And while it's open, I may try inserting a couple of diodes in series with the lamp output from the power supply to drop the voltage a tad and see if the lamps last longer. (No more dead ones today, knock on wood.)

Mostly it's just great fun to have an organ in the house at last. I was worried about next Sunday's hymns, but after some diligent work today I feel much better about them. Practice really does make a lot of difference.

[jbird604]

Continuing observations... I think we tend to get used to whatever organ we play, and as the memory of the Viscount fades, I find the Rodgers sounds better. This morning I practiced several of my hymns for tomorrow using only the 8' principal and a soft 16' on the pedals. I found myself quite enjoying the sound.

Another thing that affects my perception is TOUCH. The Viscount had "tracker touch" keyboards, which I had poo-pooed at the beginning, even considered taking those little inverted plastic caps out of it. But the Rodgers keys are actually too easy to play, and that may contribute to the perception that the tone is mushy or pudgy. I'll get used to that too, I suppose. I do wish it were possible to add a little more resistance to these rather cheap-feeling Roland synth-style keys.

It's not outside the realm of possibility to do a keyboard transplant, if I can find some better keys that can be adapted to the key contacts (rubber domes) on these keyboards. But that is probably way too much trouble. I should just find a better organ before I go that far.