Hi novabusrst, welcome to the RME forum.

Hmm … I think this is not the best combination of interfaces.

You might know already, that:
— all devices need to be clock synchronized by either digital links or Word Clock
— an application / DAW can only load one audio driver at a time

If you would use the UCX II with the USB driver as main interface, then you can only connect 8 channels of FF400 or FF800 through ADAT @single speed.

If would would use the FF800 as main interface, then you could access FF800 and FF400 through the firewire driver in parallel through Firewire. You need either WC or an ADAT link for clock synchronization.
If you access all channels through Firewire, then you have to route the channels through the DAW with the full RTL.
So, you may want to connect the FF800 and FF400 with one ADAT link.
Then you can route 8 channels @single speed from FF400 to FF800.
Advantage, then you can use the 8 channels of FF400 for the monitoring in the TM FX instance of the FF800.

Then you have 1 ADAT port free to connect the UCX II to the FF800.
But to be honest, I wouldn't connect the new UCX II in standalone mode to the FF800.
Even if you install the USB driver, connect the UCX II via USB to make it easier maintainable.
Again … I wouldn't deploy the UCX II behind the FF800.

Again, I regard this combination of interfaces as not so ideal.

TBH … I would sell all and get an UFX II or the successor of the UFX+.

Excellent target designs are based on those interfaces, and it is ideal if you can route all channels inside of one TotalMix FX instance and not having to work with three of those instances. This is also not nice from an operational perspective.

Other very good combination of devices:
— recording interface with TM FX as UFX II or UFX+ (successor)
— ADI-2 PRO FS R BE for the monitoring.
Further Extensions (Preamps, AD/DA converter) through ADAT or even better MADI.

What type of / how many channels do you need?

Sorry, this is too unspecific. You should distinguish between:

- Analog inputs and outputs (balanced or unbalanced)
- Instrument inputs (Hi-Z)
- Phones Outputs
- Mic Inputs
- Digital inputs and outputs (AES, ADAT, SPDIF (optical/coax), MADI (optical or BNC), ..)
- MIDI
- Word Clock

Only then I could get an idea whether e.g. an UFX II or UFX+ (or successor) would be sufficient.
Or whether an UFX II is sufficient with two ADAT ports or whether you need MADI.

Then why don't you draw up a list of devices? It's not that difficult. I'll explain the main differences between the analogue inputs and outputs here. You should be able to cope with this:

Microphone Inputs

Microphones need a balanced microphone input, unless you have a tube microphone with a preamp of its own that is connected to a balanced line input.

Instrument / Hi-Z inputs

If you want to connect guitars and basses directly to your recording interface, then you require a Hi-Z input (cable with TS plug). Or you have to bring the signals to line level via an external DI-box, which is then usually a balanced connection (cable with either TRS or XLR plug).

Analog Inputs and Outputs with line level

For instruments with analogue outputs or external effects units with analogue inputs and outputs, you must check the manual to see which connection type they support, either balanced or unbalanced.

As a side note: line levels are in the volt range and are over 1000 times higher than microphone levels, which are in the millivolt range.
If you are interested: on the Sengpiel page you get a converter and an overview about typical levels used i the studio.
Sorry, the English version of this page is not accessible anymore: http://www.sengpielaudio.com/Rechner-db-volt.htm

Analog Port – unbalanced connection

An unbalanced connection is made via a cable with 2 wires: signal carrying conductor and shield. The connectors are typically TS plugs (tip, sleeve). When recording microphone signals or using long cables, unbalanced transmission is highly susceptible to external interference. Here, only lower levels are used, consumer level = -10 dBV (which is only 0,3Veff).

Analog Port – balanced connection

In the professional environment of a recording studio or on a stage, balanced transmission is preferred because it allows interference-free transmission of the useful signals even over long distances. The plugs are XLR or TRS plugs (TRS=Tip, Ring, Sleeve). Here, higher studio levels are used.
In addition to ground and the wanted signal (A), there is another wire that also carries the wanted signal, but in inverted polarity (B). When summing the signals A+B, the polarity reversal completely cancels the useful signal, leaving the interfering signal. The interfering signal can then be removed via an electronic circuit so that only the useful signal remains. This requires appropriate electronics in the unit, which may or may not be present. You have to look in the manual of the connected unit.

The preferred connection type in the studio is definitely a balanced connection, if the connected devices support it. Cables for balanced connections are available in the following variants: XLR-XLR, XLR-TRS and TRS-TRS.

List of devices that you want to connect

All you have to do is make a list of which microphones, instruments and other devices you want to connect. This is best done in the form of an Excel list with the following columns:
— Device
— Manual URL
— Required inputs on the rec interface (1=mono, 2=stereo)
— Required outputs on the rec interface (1=mono, 2=stereo)
— Type: Mic | Instr | Line
— Mic Type: dynamic, condenser, ribbon
— Phantom power: yes/no (only for condenser microphones)
— balanced or unbalanced
— Plug type (TS, TRS, XLR)

Then add up
Total inputs: Mic, Instr, Line
Total outputs: Line

Integration of external Mixer

Your external Mixer might require more attention depending on how you want to use it.
Which is this for a mixer? Does it have digital ports or modules like ADAT or MADI to connect it digitally?
Do you want to record each of the Mixer Channels, some mixer have a CUE out port for each channel?
Or so you would like to record several submixes of the mixer or only the Stereo Sum.

Diagram for a better overview over your planned setup

Furthermore, a drawing of your intended Setup would help to give an overview, how you want the devices to be connected to each other.

General considerations

RME interfaces, usual port layout

The largest RME USB recording interfaces have a maximum of 4 microphone inputs, which can also be used as instr/line inputs. Plus 8 analogue inputs and outputs.

Upgrade port capacity with external units

If the ports on the recording interface are not sufficient, you have to upgrade as external devices, if you don't want to permanently reconnect. Usually, this type of device:
a) Mic Preamp(s) to get more Mic and Inst inputs. Often, you also get 1-2 headphone outputs, which is very practical for fellow musicians.
b) AD/DA converters to get additional analogue line inputs and outputs. If you mainly connect keyboards and synths, you might need more inputs than outputs. In that case, devices like the RME M1610-Pro are ideal because it has more inputs than outputs.

Connecting external devices

For the digital connection of external devices, there are essentially 2 possibilities (I'm excluding AVB because it requires additional network components):
a) ADAT = 8 channels at single speed (44.1/48 kHz), 4 channels at double speed (88.2/96 kHz). Often one ADAT channel can also be switched to SPDIF protocol (2 channels 44.1-192 kHz). Cable: TOSLINK, cable length according to standard up to 10 m, 15 m usually works as well.
b) MADI = 64 channels at single speed (44.1/48 kHz), 32 channels at double speed (88.2/96 kHz). Cable: multimode or single mode (laser). Cable length up to 2 km (single mode: 10 km) between each unit. Up to 8 units can be connected serially to one MADI bus. So, cable from unit to unit and back to the recording interface.

Influence of sample rate on the number of useable ADAT/MADI ports

As you can see, it also depends on the sample rate you intend to work with. The number of analogue channels directly at the recording interface always remains the same, regardless of the sample rate used. However, if you connect external preamps and AD/DA converters, the number of channels is halved for ADAT and MADI if you want to work with double or even quad speed. Basically, single speed up to 48 kHz is completely sufficient. You should only consider this beforehand.

Personally, I am a fan of performing a high-quality and transparent A/D conversion as quickly as possible. Then you have the best quality digital audio signal in your DAW for further processing.

RME converters are known for being transparent and not changing the sound. If you want a certain “mojo” or more analogue vibe, you could send the signals to a summing box later and re-record the signal from the summing box. You just have to know, or try out by listening tests, whether this is really worthwhile.

I can't say anything about the differences in sound between old and new devices.

But if you want to compare the technical data of different FW/USB/TB interfaces, the quickest way is to use the Excel spreadsheet I provide in this blog article. Please note that PCI/PCIe cards and AVB/Dante interfaces are excluded from consideration. https://www.tonstudio-forum.de/blog/Ent … B-MADIfac/
Direct link to Excel: https://www.tonstudio-forum.de/attachme … 4-08-xlsx/

You can, of course, combine the existing recording interfaces as you like, with the FF800 as the main interface, because it is the only one with 2 ADAT connectors.
But keep two things in mind for your monitoring:
You cannot route HW inputs and SW playbacks between the three TM FX instances. You need digital ADAT connections between the units to be able to route up to 8 channels per ADAT port to the main interface.
Then again, you have the flexibility to route HW inputs and SW playback channels to a HW output of the main recording device.
Otherwise, you have to route through the DAW at full RTL, this can lead to higher latencies with larger ASIO buffersizes.

For some of my applications I need to route some audio channels very fast from inputs to outputs (amp, headphones, ...).
This is only possible if you can route the signals directly from the inputs to the outputs of the recording interface.

Even if the latency of converters is lower than the latency via FW/USB between computer and recording interface. Also note that older recording interfaces have slower converters built in. Since they will be recording at single speed, they will also have the highest converter latency.

The technology has evolved over the years.
The different latencies of the converters can also be found in the Excel file.

To have ultimate flexibility and not have to “struggle” with 3 TM FX instances. I recommend using a larger recording interface and thus only one TM FX instance, then you can also route each input and SW playback channel (from the computer) to each output on the recording interface.
This would also give you up-to-date / fast converters for AD/DA.

Then it's just a question of whether to go for UFX II or something like UFX+, depending on how many external devices you want to connect. As I mentioned earlier, MADI offers more flexibility, at a slightly higher cost, of course.

The other question is … if you spend more money on the recording interface, wouldn't it be better to calculate with some reserves and spend a little more money to have the possibility to expand via MADI. In my opinion, such an investment is more sustainable in the long run.

My current setup, if you are interested: