The HDSPe MADI FX is a very fine card, I had it here for a test, but finally preferred the UFX+ as main interface.
You can check out my review here, download the PDF there:
https://www.tonstudio-forum.de/blog/Ent … Pro-FS-BE/
Forget about ADAT, you need a MADI-based interface
ADAT = 8ch@single speed, 4ch@double speed, 2ch@quad speed
MADI = 64ch@single speed, 32ch@double speed, 16ch@quad speed
For 64 analog ports IN/OUT, you need 4xPulse16 with the MADI option.
At single speed one MADI bus would be sufficient, then you could even use an UFX+.
But if you intend to record at double speed, you require a 2nd MADI bus.
I prefer optical over BNC cabling because then you have automatically galvanic isolation, and you can also use longer cables (multimode fiber, OM4 or OM3) up to 2 km between each of the devices! Patch cables are available up to around 30 m.
For this purpose, the HDSPe MADI FX is an excellent card, it has already two optical ports and as an option, you can get a 3rd optical card for in total 3 optical MADI busses with 3×64ch at single speed / 3×32ch at double speed.
As an option, you could consider adding an ADI-2 Pro FS R BE to the setup (you can use the AES port of the card), then you have an ideal device for the monitoring section. Finest quality and very useful features.
Also, useful to add an ARC USB to the setup.
If you consider adding ADI-2 Pro to the setup, then you can e.g., switch between monitors and headphones by remapping the front keys, I am using this configuration: https://www.tonstudio-forum.de/blog/Ent … our-Setup/
An option is to switch between monitors and headphones by using the ARC USB. Then you need two ways for audio entering the ADI-2 Pro (AES and ADAT). ADAT you could achieve if you use the ADAT OUT port of one of the ferrofish devices.
Then you can configure the ADI-2 Pro to send audio coming in from AES to the monitors and audio coming in on ADAT to the headphones. Voilà, now you have a very nice control through the ARC USB to switch between the ports. I described it here: https://www.tonstudio-forum.de/blog/Ent … ort-DE-EN/
When integrating the ADI-2 Pro it's additionally useful to have volume for monitoring under better control.
It's quickly possibly to accidently move fader to 0dB in TM FX. With the ADI-2 Pro you can leave the AES and/or ADAT outputs to the ADI at 0dB in TM FX and fully control the volume at the ADI. And the 4 reflevel design plus auto reflevel it gives you on top always optimum SNR and dynamic for your monitoring.
BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub14