RME Fireface UCX: Frequently asked questions.

Is the Fireface UCX the successor of the Fireface UC?

Is the Fireface UCX the successor of the Fireface 400?

Can I use the Fireface UCX stand-alone?

Can I use the UCX on a USB and FireWire port at the same time?

What is better: USB or FireWire?

Can I use the UCX on a FireWire 800 port?

Can I use the UCX on an USB 3.0 port?

What performance can I expect from the USB bus?

Can I use the Fireface UCX with bus-power?

Can I connect more devices to the same USB bus

Can I use the Fireface UCX together with other RME FireWire or USB hardware?

How do you calculate all the effects? Inside the famous RME FPGA?

Will you open the DSP to 3rd party developers?

Is the volume knob an analog attenuator positioned after the DAC, or is it a digital level change?

If the host computer crashes and goes into a mega decibel noise burst loop can I still control the volume at the unit?

How does AutoLevel work? Does it mean that 0 dBFS peaks are 100% avoided with AutoLevel turned on regardless of source input level?

Is it possible to use two or three UCX & Fireface to get more channels?

I couldn't find any information about latencies introduced by the FX-section.

Is the Fireface (UCX) compatible with Pro Tools 9/10?

Is the Fireface UCX the successor of the Fireface UC?

No. Despite the same form factor, the Fireface UCX is a completely new device with an expanded feature set for studio and live usage. The UC still remains as a state-of-the-art USB audio interface.

Is the Fireface UCX the successor of the Fireface 400?

No. But with the end of the production of the very successful Fireface 400 the Fireface UCX is the perfect choice for users who look for a FireWire interface. It provides all features - including the X-Core with FireWire support - the latest TotalMix with the complete UFX effects engine and and much more.

Can I use the Fireface UCX stand-alone?

Yes. The Fireface UCX can be used without any connection to a PC or Mac. It has a memory for 6 different configurations. It can even be controlled by the front knob and via MIDI. In Class Compliant mode it also works as a professional two or eight channel interface for Apple's iPad/iPad2.

Examples:

• 10-channel AD/DA-Converter
• 2-channel Mic Preamp
• Monitor Mixer
• Digital Format Converter
• Analog / Digital Routing Matrix

Can I use the UCX on a USB and FireWire port at the same time?

No. With simultanious connection the port is used which is initialized from the operating system first. For example for the installation of the FireWire driver it's necessary to disconnect the USB cable.

What is better: USB or FireWire?

Only a test on your individual system can show. Theoretically the UCX will perform equally well on both connection protocols. Note that USB works best on up-to-date computers, while FireWire might have an advantage on older computers.

Can I use the UCX on a FireWire 800 port?

Yes. You just need a plain FireWire 800 <> 400 cable or adapter. The FW 800 port is fully downward compatible to FW 400.

Can I use the UCX on an USB 3 port?

Yes. The Fireface UCX is compatible to USB 3.

What performance can I expect from the USB bus?

A Fireface UCX can achieve a performance similar to a PCI or PCI Express card when used with an optimal PC. Low CPU load and click-free operation even at 48 samples buffer size are indeed possible on current computers.

Like any audio interface the Fireface should have a data transmission to the computer as undisturbed as possible. The easiest way to guarantee this is to connect it to its own USB bus, which should be no big problem as most USB 2.0 interfaces are a double bus design. See the manual for details.

Can I use the Fireface UCX with bus-power?

Only via FireWire. USB does not deliver the necessary amount of power.

Can I connect more devices to the same USB bus?

Most devices do not pose a problem. Even devices with higher bandwidth requirements like hard drives will usually work as the audio interface has priority. Simply check it out.

Can I use the Fireface UCX together with other RME FireWire or USB hardware?

This feature is included but not officially supported. Use at your own risk. All RME FireWire and USB interfaces use the same drivers respectively, so can be used together in an ASIO application. It only needs a hardware clock sync via a digital I/O (ADAT/SPDIF) or Word Clock I/O.

So while it should be possible to use e.g. a UCX with a Fireface UFX, 800 or 400 (FireWire driver) or a Fireface UFX, UC (USB driver), bandwidth limitations and other real-world problems might bring up various problems. In that case RME will not be available for help and support.

How do you calculate all the effects? Inside the famous RME FPGA?

No. The Fireface UCX has a dedicated and very powerful Texas Instrument Floating Point DSP which is used for everything except routing/mixing, which still happens within the FPGA.

Will you open the DSP to 3rd party developers?

Definitely not.

Is the volume knob an analog attenuator positioned after the DAC, or is it a digital level change?

The level is changed in the digital domain for various reasons. An analog attenuator suffers from many issues:

- No reproducible gain setting. The RME design provides a digital control and recall of all settings. This has many advantages, not only for the interaction with TotalMix on the host computer.

- No error-free gain operation and linearity problems: analog attenuators (potentiometers) never match 100% between both stereo channels. But even within the range of one channel the pot never operates perfectly, especially at the end (highest/lowest) position.

- Scratch and dropout noises: Typical mechanical problems of potentiometers and/or switches within the audio path.

- Limited to stereo control. Pots are usually limited to stereo. The digital control makes it easy to perfectly control a 5.1 setup from one knob, like the UCX volume knob.

- Change of frequency response in the extreme settings. High resistance at the lower and/or higher positions generate high or lowpass filter functions that will change the sound.

These disadvantages compensate any theoretical loss by the bit resolution. Which is by the way just digital theory, having no proof in the real world. Lower volume signals will just vanish within the DAC noise floor, but not cause distortion or other artifacts. With a SNR of 118 dBA at its outputs the UCX has a lot of dynamic range for matching monitors over a wide level range without its noise being hearable. Simply said: if you cannot hear its noise, then you cannot hear any digital level control artifacts. And if you could, you would just hear noise, nothing else.

If the host computer crashes and goes into a mega decibel noise burst loop can I still control the volume at the unit?

Yes. The UCX cannot 'crash' internally, the big volume knob will work even if the PC/Mac crashes. This way no external controller is needed to prevent damage of speakers and ears.

How does AutoLevel work? Does it mean that 0 dBFS peaks are 100% avoided with AutoLevel turned on regardless of source input level?

AutoLevel works completely digital and therefore can not prevent hardware overload and clipping on the analog input stage. AutoLevel is designed as slow volume tracker, but with faster settings can also have an effect similar to a Maximizer. It can also operate like a Peak Limiter if set up accordingly. Basically it works as gain raiser, while a compressor works the other way round, as gain reducer.

If used on the Hardware Outputs, AutoLevel can prevent too high output levels. The mixer's internal processing can generate levels of up to +24 dB without clipping (internal mixer headroom), so the output faders have to be pulled down to avoid hardware output clipping. See factory preset 'Output Protector' to get such output protection from overload.

Is it possible to use two or three UCX & Fireface to get more channels?

In real-world operation more than one unit can lead to problems on the USB and FireWire bus, caused by the high number of channels.

The Fireface 800 uses FireWire 800 to support multiple unit operation. But there are many reasons why it can fail or not work optimally. We have also repeatedly seen people using it the wrong way - 3 units and each unit only used with the 10 channels analog I/O, completely overloading the FireWire bus, where one should have simply used the additional units in standalone mode connected via ADAT.

For these and a few more reasons, like the comparable bandwidth on USB with multiple units, the separated TotalMix per unit and the Monitor Controller which is only needed once, we decided to use a FireWire 400 interface with the UCX and no longer support this kind of operation. The unit has enough channels for most applications. In our opinion it makes more sense to connect external AD/DA converters - a 2nd or 3rd UCX is also possible - to the ADAT I/Os of the (first and only) UCX, adding up to 16 channels of analog record and analog playback.

In short: multiple units might be possible, but are completely on user's risk. So if it doesn't work we can not help.

I couldn't find any information about latencies introduced by the FX-section. Does there exist any exact data? It would be very interesting to know how many samples of latency are introduced by each effect (EQ, Dynamics).

There is no further delay, all effects are calculated real-time.

Is the Fireface (UCX) compatible with Pro Tools 9/10?

Yes. There is no specific "compatibility" with PT 9. PT 9 works with audio cards that use standard ASIO and Core Audio drivers, which includes all RME devices.