Hi Dave,

welcome to the forum. Impressive, 15y of use, wow.
What do you mean by mixing hybrid?
Is for you a certain requirement bound with that?
What is your total budget for such a solution?

In this blog article I offer an excel sheet which contains a comparison of different USB/TB based recording interfaces:
https://www.tonstudio-forum.de/blog/ind … B-MADIfac/

Did you ever have a look at the UFX II or UFX+ which gives you a wide range of options to expand your setup ?
Both offer
- 8x analog I/O (at all sample rates, single speed up to quad speed)
- 2x ADAT I/O for 16ch in single speed, 8ch in double speed, 4ch in quad speed
and the UFX+ additionally
- 1x MADI (optical and/or coax) for additional 64ch in single speed, 32ch in double speed, 16ch in quad speed

These devices you could e.g. expand via ADAT in the following way:

a) with your old FF800 in stand-alone mode via ADAT to
- additional 8x analog I/O (Total 16 analog I/O ports)

b) with another 8 ch converter like the ADI-8 DS MK III (https://www.rme-audio.de/de_adi-8-ds-mk-iii.html) to
- additional 8x analog I/O (Total 24 analog I/O ports)

to finally have 3x 8ch = 24 analog I/O at single speed (44.1/96 kHz).

Recording in double speed (88.2/96 kHz) needed?
Then you need to connect the external converter with 2x ADAT because of the channel multiplexing.
Then this setup would be limited to 16 analog I/O.

If you need more flexibility in your setup then you should take a look at the UFX+ which offers
- additional 64ch more by MADI, optical and/or coaxial (if you do not use WC)
- having two different choices to connect to a computer, either by USB3 or Thunderbolt; or even USB2 (limited to 30ch)

MADI gives you the additional flexibility to reach equipment which is not close to your recording interface.
With MADI you build up a ring structure, from one device to the other and back to the recording interface.
Such an optical OM3/OM4 cable may be up to 2km long between each of the up to 8 devices in such a ring.
OM3/OM4 fiber optic Patch cables are available up to around 15 or even 30m.
Such optical fiber cable gives you also galvanic isolation.

So you could also think about such an upgrade:
- sell FF800 and Firewire card to refund the new hardware
- get UFX+
- get an 8, 16 or 32ch converter with MADI I/O which matches your needs

Then you have still MADI, ADAT, AES channels available for connecting other stuff like e.g. ADI-2 Pro.

Further information of the RME flagship interfaces you can find here in my blog:
https://www.tonstudio-forum.de/blog/ind … 8-RME-UFX/

An overview about my use cases with an UFX+ and MADI setup you can find here:
https://www.tonstudio-forum.de/blog/ind … -DURec-DE/