Hi !
I have exactly the same problem (I Think)

The Front Input 1 is making some Hiss/Noise clearly earable and viewable on TotalMix. The Green Led "Signal" is awlays bright too.
The Rear Input is totally clean, no noise, working perfectly...

I Sent back my FireFace 800 to the Store where I purchased it. They sent it to RME's SAV. I'm waiting for some news I'll tell you.

So looks like this is a common problem. I quite liked the front input in channel1 as it gave me a descent signal for bass (which is my main instrument), allowed me flexibility in recording multiple sessions/setups and I felt sounded better than the preamps in my Tascam M2600 mkII. I suppose I will simply stop using the front channel1.

Would it make sense that the other front inputs could suffer the same fate? Or perhaps the Channel1 guitar input is a different makeup?

Sending it off for repair is not something I want to do as I can't be without an interface. I'm in Toronto, Canada.

Must say that for all the good things about the FF800 I am dissapointed in this.

I do have a tech friend and first chance I get will open the FF800 up and see if there is a cap that seems to be going.

Same problem here.  I guess I'm not alone either.  I have to admit, I'm disappointed by this seemingly common hardware issue.  I figured that mine was just an isolated issue until I stumbled upon this thread.   

I purchased my Fireface 800 brand-new about 3.5 years ago and have also begun to experience noise on the channel 1 pre-amp, accompanied by it's dull glowing green input signal LED.  Nothing audio cables are plugged in, the Speaker Emulation/Limiter/Drive are turned off, and the preamp gain knob is turned all the way down.  I've only used the Fireface in my smoke-free home studio since I purchased it.  The noise is relatively low-level, (about a 13 db increase in the noise floor), but unfortunately it's still there eating up space.  The noise begins a few minutes after the unit has been powered on.

I called Synthax/RME today and was advised that it's probably a hardware issue that will require repair.  I'm waiting on a call-back to discuss the results troubleshooting steps given to me by the technician.

I migrated to RME from a MOTU PCI-based system.  The MOTU system ran flawlessly for the 8 years I had it.  I just wanted an upgrade (stable interface, better converters, solid build quality) so I splurged and got the FF800.

 
Hope that RME/Synthax can help me...

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