I own both RME FF400 and Native Instruments Audio Kontrol 1. In the past 5 years the FF400 has given me nothing but problems. I have hardly used and today it died on me. By contrast, my AK1 has been used literally every day for 5 years and it's still going strong.
The main advantage of NI over RME is the drivers, because NI have implemented truly multi-client drivers, which means you can have several DAWs use the sound card SIMULTANEOUSLY and at the same time have it configured as you system default audio device to play mp3s or whatever. NI support any number of clients. RME claim that their devices are ASIO multiclient but you cannot have two apps sharing the same internal input of Totalmix, which means that you have to manually select the inputs for this to work, otherwise you get crackle. The NI driver simply welcomes new clients and allows them to share the outputs, it's totally hassle free.
Note also that the vast majority of ASIO audio interfaces DO NOT SUPPORT multi-client. This means that you'll need a separate sound card to use as your system sound card, which if you ask me is a PITA. NI's sound cards are just very practical.
Another benefit of the NI cards is that they don't get hot at all. RME Fireface runs so hot you can't keep your hand on it, this is not an exaggeration. For this reason, I can keep my AK1 tucked away in a confined space without fear of overheating, and it has never given me any trouble, it just works every time. If I press play I know sound is going to come out of my monitors. I tend to forget the AK1 it's there LOL. I can't say the same about the FF400, when I press play it's a lottery. In a way I am glad it died. I'll probably fix it and sell it on eBay.
Another thing to note is that my FF400 crashes quite regularly and stops working after my computer resumes from sleep. This does not happen with the NI cards. I also have a Kore 1 which has a built in sound card and essentially works equally well.
The electronics of the FF400 are higher grade though, this should be noted for professional recordings. For me NI's stuff is good enough. I think the new RME USB cards e.g. Fireface UC may be better. With Firewire I've had loads of DPC issues and BSODs back in the XP days. Since the use of USB is more widespread (it is impossible to buy a computer without USB ports, but it's hard to find one with Firewire ports!) I can only assume that USB will be more reliable as it's been tried and tested. However, RME's USB cards require external power (I like the way most of that power is converted to heat
), whereas NI's cards all run off the USB, which makes them suitable for mobile/DJ/location work.
I believe the old AK1 has better electronics than the new KA6. The layout seems better on the KA6 though, and I suspect the build quality may have been improved.
So, in short, my next audio interface is going to be a Native Instruments KA6 or another AK1 which I can get for very little money.
Incidentally, the big knob on the top adjusts channels 1/2 level, how do you adjust channels 3/4 on this thing?