Yes, I can guarantee that all Physis Viscount organs have the exact same hardware/software platform.
This also includes Overture 468 and Unico 800, and some custom models.
In American version there is also a three manual model with complete super and sub coupler: Unico 600.
The sub/super couplers are also in demand here in Europe, in England, where Regent builds custom organs, often with these couplers.
Yes, there would be no technical limitations for equipping a smaller model with sub/super couplers.
In another post I explained that the only determining factor is the amount of "polyphony" that can be reached with the number of DSPs installed.
To better understand, I will explain how the physis hardware is structured.
There is a motherboard, identical for all models: on this board there are the interface connections with the external controls (keyboard and pedal encoder, display, Pistons, stops tab, etc.).
On this motherboard, up to 7 cards can be inserted vertically which have different functions.
Starting from left to right:
1) DAC/Mixer board. This card exists in different versions, depending on whether the organ has more internal or external audio channels.
2) Sampled orchestral voice card. It is identical in all models, and contains the sampled sound data for orchestral voices. It has the flash memory in which the samples are stored, a RAM memory, and a sound generation chip exclusively for these voices.
3-4-5-6), These are 4 slots where to install the cards that contain the DSPs for sound computing of physical sounds. These cards exist in two versions: with two DSP (those commonly used), and with four DSP (often used in models with sub/super couplers).
Of course the number and type of cards installed depends directly on the maximum polyphony that is needed. So in the smaller two-keyboard models, two cards with two DSP each are sufficient (occupying only two slots), while in the models with many sub/super registers and couplers four cards are generally used, and the cards are with four DSPs each (or they can be a combination of these two types of cards, for example two cards with two DSP, and two cards with four DSP). Each of these cards in addition also contains a slave CPU and a ram memory.
7) CPU card. Contains the master CPU, a flash memory in which is stored O.S. and the physical voice files, etc.
a RAM memory, USB management chips, clock chips, the CR2032 lithium battery to power the clock when the organ is off.
This card is identical in all models.
Theoretically, it is possible to add sub/super couplers even in organ without it.
If the couplers are used in the same keyboard WITHOUT coupling more keyboards between them, theoretically it is not necessary to add DSP card's (or replace the DSP cards with the model with four DSPs, assuming that currently the organ has four cards with two DSPs). This is because the polyphony with the sub/super couplers in each keyboard (separately, without coupler the keyboards between them), is almost identical to the polyphony necessary with Tutti without sub/super but with coupler keyboards.
You can build a small accessory (for example with Arduino) to connect with MIDI, with tabs for sub and super couplers.
When a key is played, this accessory sends back (via the MIDI IN jack of the organ) the key data to the upper or lower octave.
If instead you want to use the crossed sub/super couplers between the keyboards, the necessary polyphony is superior and it will be necessary to add or replace the cards with the model with four DSPs.
There are also exclusive MIDI codes that Viscount uses for the internal management of the sub/super couplers, but I'm not sure that these messages are also implemented in models without these couplers. I should check ..
If this were the case, this accessory could be programmed to send these messages and the organ would internally manage the couplers (and in this case it would be enough to connect only the MIDI IN cable of the organ).
Of course, the software recognition of the number/type of DSP card is automatic (plug and play), this means that you can add or replace cards on an already purchased organ, without any type of manual update. The software will automatically recognize additional DSP cards.
