I have an RME UCX (same as UC but it has built in FX). I love mine. I would definitely get the UCX over the UC myself. I use those FX when mixing live.
 
If anything happened to my UCX, I would immediately replace it with another RME.
 
It can record two musicians with vocals with built in Pres (2 for mics, 2 for line ins).
 
I hook up an Audient ASP880 to mine. I also have an RME Quad Mic Pre to serve as a pre-amp for the additional 4 analog line ins on the back. It kinda makes it like a UFX, taking up a full 1U rackspace (1/2 for the Quad Mic Pre and 1/2 for the UCX). If I'd had the money all at once, it probably would have been better to go with the UFX.
 
But as it is, I can plug in my old Tascam 2488 to the UCX SPIDF port (this adds 8 more) and record 24 tracks at 44.1. That's enough for me. I need to borrow mics to get there. :-)
 
And I have often tossed it in my backpack and pedaled to a friends house with everything I need for a jam. :-)
 
When shopping, I suggest using the 'get quote' feature available on a number of pro audio sites to find out what they are actually charging for the UCX. You might pay less for a UCX than you might for a UC if you shop around.

I just checked this at 44.1.
My UCX gets
3.7 msec round trip at 48 sample buffer.
4.5 msec round trip at 64 sample buffer.
5.9 msec round trip at 96 sample buffer.

rumleymusic

then why does usb3 exist?

especially if no one is using it?

 
I use it all the time with hard drives.  I love the "speed."  Of course speed is not the right term.  More data at once (bandwidth) is more accurate.  I can run 30+ channels of 192kHz audio with my RME UFX on USB 2 at low latency.  It would not be any faster with USB3, Thunderbolt, Ethernet, or Magical Voodoo.  
 
RME does use USB3 with their 394 channel  Madiface XT.  That one probably needs it, so they used it.  
 
That is what is great about RME.  They don't try to trick you with gimmicks like two channels of thunderbolt audio, they just offer practical, high performing gear.   

A bit OT but the UFX is such a great unit. Early this year I sold my two FF800s and bought a UFX + remote. Totalmix is an awesome piece of driver software to go with it.

In addition to the FX on the UCX it has an 'AutoLevel' feature on 4 channels which is nice.
 
@Mike V., make sure you check out RME DigiCheck. You get that as well as TotalMix.
http://www.rme-audio.de/downloads/driver/digicheck.php
 

Do people use the headphone outs (on the Babyface) as "normal" analog outs? (into a mixer for example?)

 
 
It can be done, even if it is not recommended as a general practice due to balancing and impedance issues.  The quality of the DA on RME's headphones has always been equal to the rest of the box and the amps are very good.  Many companies skimp.  Low latency is not a problem, at least as far as the hardware goes.  

music,
I think it's more about what the round trip latency time is - for a given sample buffer size. Let's assume that the more tracks/vsts you have, it's up to your PC to supply the grunt - but it seems that not all audio cards are created equal when setting latency to, say, 64 samples.
I've never used a USB audio interface before - I've always had PCI. It seems that USB interfaces generally have higher latencies for, say, 64 sample settings - than a PCI card would have. This is where a better driver will give you lower latencies for the same "sample buffer" settings.
 
Does that make sense?

If you have a well-configured current generation machine, you can run pretty substantial loads at low round-trip latency.  I leave my MOTU Ultralite AVB set at the smallest buffer sizes.
Rarely do I need to increase it (only on the most dense of projects).

Jim Roseberry
If you have a well-configured current generation machine, you can run pretty substantial loads at low round-trip latency.  I leave my MOTU Ultralite AVB set at the smallest buffer sizes.
Rarely do I need to increase it (only on the most dense of projects).

Jim - you're really helping to steer me to the Ultralite AVB. It seems to be pretty similar to the RME Fireface UC, that I've also been looking at - but with the Fireface UC being 5 yrs old (or so), I'm thinking the newer Ultralite AVB might be a little better "future proofed".
 
I agree with Michael - if it weren't so expensive for a "good" (esp drivers etc) audio i/f - I wouldn't worry so much about "future proofing" ;-)

Jim Roseberry
You might (also) want to checkout MOTU's new Ultralite AVB.
Low round-trip latency, solid drivers, and noise-floor of -112dB.

Quick question on "noise floor" as I have seen this comment made a few times (as a differentiator). When I got my interface, this article by Focusrite caught my eye, which basically says that many manufacturers quote the chip itself, and not how it performs in the system (which can be up to 12dB different).
 
Isn't this pretty much splitting hairs anyway, since in a digital realm this is so much lower than analog (i.e. the digital floor is so low it is almost "immaterial" as a differentiator)?

I also think of noise floor in terms of softer/quieter tracks/parts like classical guitar, whispered vocals, etc.
If I get any noise, an expander will help, but I try to avoid that.
Michael

Ditto! I don't really want all the cables sticking out on 3 sides (4?). I like to have all on the back with 2 mic/guitar and 2 phones on the front.
Michael

The math

rumleymusic

And why USB3 or USB3.1, because there is much more voltage and ampere in it. You can get more steady power.

 
Yeah, you can get a little more current at 5 volts DC with USB3, and that is helpful for low noise.  The nice thing about the preamp chips in the RME is that they run naively off of 5 volts rather than needing conversion to 18 like most analog controlled preamps, though they suck up a significant amount of current to compensate.  It is a little more compact.  I personally would never trust bus power to begin with and would probably keep the thing plugged in at all times.  

Amperage is inversely proportional to the voltage. If the transformer is in the device (interface) it shouldn't change the load on the usb port. Total watts are equal on both sides of the transformer. P=IxE. Voltage conversion shouldn't be a factor after it leaves the usb port.
 
Rocky

gswitz
In addition to the FX on the UCX it has an 'AutoLevel' feature on 4 channels which is nice.
 
@Mike V., make sure you check out RME DigiCheck. You get that as well as TotalMix.
http://www.rme-audio.de/downloads/driver/digicheck.php
 

Yes. I've had RME gear for over a decade and been using Digicheck for ages too. It's a great diagnostic tool, not to mention a great vanilla recording interface for live work.

jbraner

but the AVB feature simply sets the unit above the Babyface.

 
Albert,
AVB (on the Ultralite AVB) only works on Macs right now. I don't know how easy or hard it will be to get this working with Windows...

John,
 
I was reading about the AVB feature. One way the Ethernet can be used (if not using the USB) is to connect it to the Mac.
 
The one I was referring to is the AVB feature is to expand the inputs by using two Ultralite AVB and connect both units via the Ethernet cable, I believe this is possible for both PC and Mac ?
 
http://www.motu.com/products/avb/ultralite-avb/networking.html