ALLEN MOS-1 or MOS-2?

[praestant]

Hallo, what are the tonal differences between a Allen MOS-1 and a MOS-2 ? And which organ sound "better"? And which requires less maintenance?
Thank you for your help.

[myorgan]

Praestant,

It depends on the model(s) you're talking about. However, in general the MOS-2 is a multi-computer organ which allows one to create a genuine Celeste from the stops. Other features that were optional on the MOS-1 (like a card reader) were made standard on the MOS-2. Delay was added in the MOS-2 era to simulate pipes in a chamber where certain groups of stops are closer to the audience than having all sound exactly at the same time. Delay, in general, caused the stops from one computer to speak slightly after the other, creating the effect of distance. A full, moving capture action was also standard on the MOS-2, whereas some of the MOS-1 organs had either pre-sets or blind capture action.

Those are just a few of the differences I can think of.

Michael

[Organkeys Jones]

Hardware changes & model numbers rather than tonal upgrades were the main differences. A few corrections to myorgan's post: MOS-2 still had single computer models (100-300 series), still had a couple of models with blind presets, the single computer 305 had an analog celeste generator just like the MOS-1 301. The multiple computer models started with 505 (replacing the 603). 705 (2 manual) had 3 computers, but one was just for mixtures. One tonal change was not having Flute channel with just flutes, and a Main channel with just principals & reeds. Instead, the 8-4-2' choruses were split up. With frequency separation, the choruses were richer on even single computer models as compared to MOS-1. Allen was (and is) always so much farther ahead in technology than other organ builders.

[myorgan]

A few corrections to myorgan's post: MOS-2 still had single computer models (100-300 series), still had a couple of models with blind presets, the single computer 305 had an analog celeste generator just like the MOS-1 301.

That's the reason I opened with the following statement:

It depends on the model(s) you're talking about.

Of course, beginning with the 805 and higher model numbers, the number and use of computers increased, along with the increased tonal possibilities and ensemble. I could be wrong, but I don't recall MOS-1 organs having stock 3-manual models other than the 632. I believe most (but not all) 3-manuals were custom in the MOS-1 era, as was the Allen in the Amphitorium at BJU in the 1970s. The MOS-2 era had several stock 3-manuals to choose from.

Michael

P.S. In retrospect, I seem to recall a member of the Forum acquiring an Allen Model 1800 which was a 4-manual MOS-1.

[radagast]

I distinctly remember 3 manual stock models in the MOS-1 era. The very first Allen digital organ I heard was a 900 series that had 3 computers. I had literature on the 1200 and 1500 models which were three manual. Btw it was at Griggs Music in Davenport Iowa where I heard it. The sales person was Michael Dunne (I think that was his first name). He ended up opening Dunne Music in Florida, which was, or is, one of largest Allen dealers.

[Organkeys Jones]

mrdc2000: Say what?

myorgan: The MOS-1 632 was a strange combination of only 2 computers to get three manuals. But the 900 and 1200 series were also stock 3-manual models. You are right about the larger custom organs. I had a MOS-1 1204 for a while. It was basically a 1203 (3 manual, 4 computers in a possibly "F" console which was larger than a "C") PLUS a 4th manual with external SDDS tone generators for the Solo manual. The SDDS was gone when I got it. I MIDI'd the Solo and Swell, to have sounds on the Solo.

[jbird604]

Hard to really answer some of your questions definitively. Keep in mind that Allen clearly said that MOS-2 was simply a "re-packaging" of the same technology as MOS-1, and there are no differences in the way the tone is generated. The primary differences consist of some stuff that was optional in MOS-1 being made standard equipment, as well as the use of the most refined versions of the various components.

(1) The so-called "second church" stoplist, which was optional in MOS-1, such models being called "-3" ("dash three") models, was adopted as standard in MOS-2. This revised stoplist has a slightly mellower sound due to the higher-pitched stops being softened a little. MOS-2 also has a little different set of reed stops, in particular a Cor Anglais in the great, replacing both the Krummhorn and the Schalmei of original MOS.

(2) Frequency Separation was an option in MOS-1, a slight detuning between the two channels. All MOS-2 boards have this feature by default, which gives a bit of pitch offset among the stops for a richer ensemble effect.

(3) Delay, slow pedal, and a few other subtle effects that required extra boards on MOS-1 were now incorporated directly into the basic MOS-2 system.

(4) The card reader was standard on all models, even the cheapest.

(5) DAC boards were of the most advanced design, and all had both bass and treble controls for each channel.

MOS-2 was IMHO a nice upgrade, giving away basically for free the extras that people had to pay extra for on MOS-1 models. Along with these extras, there were notable sonic improvements, not the least of which were the two EPROM sockets on each MOS board. Most of the 16' and 32' stops resided on these EPROMs, as did all the mixtures, so these stops could be more detailed and varied, with some options available for those who wanted to select specific stops for those slots. This made it easier to customize a MOS-2 model, but this capability was mostly used to augment the stop lists of the larger models.

The better DAC, cleaner power supplies, consolidating certain functions onto fewer boards, the elimination of the double row contacts for second computers, and other design changes tend to make MOS-2 models a bit quieter and a bit less trouble-prone.

The downside is only that the boards are less common out there on ebay, so it could be harder to find a spare if needed.