Topic: Fireface 800 Loopback Volume Question


I'm running Logic 8.0 with a Fireface 800 (via firewire).

My principal stereo output in Logic is 1+2 which goes via the TotalMixer to my studio monitors.

Sometimes I like to output a channel in Logic via 3+4 so that it can be looped back in TotalMixer and re-recorded through another Logic channel with 3+4 as it's input. (Fairly basic stuff).

I have routed this in TotalMixer - the labels have turned red - and it works....


I have noticed that the re-routed signal is a few dB lower that the direct signal, and I have no idea why.  I don't know whether this is something about Logic or something about the Fireface.  I have tried playing with the Level In / Level Out gains in the Fireface Settings dialog box, but this has no effect.  My faders in the TotalMix are all set-up correctly and stand at 0, so theoretically there should be no signal alteration at any point.  My Logic is set up with Software monitoring, but the Logic faders are also set correctly to 0, and shouldn't be altering the signal.

As a sidenote, I have also noticed that my digital piano coming in on inputs 1+2 is much lower in volume than it should be - but perhaps that's a different problem.

Any help would be appreciated.


Re: Fireface 800 Loopback Volume Question

The analog levels of the Fireface tend to be on the conservative side, such that 0 on the mixer is somewhat less than what you'd expect for a standard +4 dBm or - 10 dBv level.  If you are seeing a level discrepancy, you should adjust the TotalMix faders until you are seeing the level you wish.  Since you are doing an analog transfer using the loopback method, you aren't getting a bit-for-bit exact transfer anyway, so you are not really going to lose anything by adjusting levels in this way.

You might try doing a loopback using the SPDIF connection, to do a digital transfer that would be both bit accurate, and also would avoid the analog level differences introduced by the Fireface' analog ins and outs.

As far as your piano, yes, that is a different issue, having more to do with the level the piano puts out, and the input setting (in Settings) you have for the Fireface.  Again, the Fireface input levels being on the conservative side, you might have to adjust the incoming level using TotalMix to something above "0", to get the working level you require. 

On the other hand, pushing levels to the max in a multi-track project makes mixing more difficult later on, as you'll find that your faders are all going to be down where their resolution isn't the most fine.  I don't use Logic, but if you are hitting an average RMS level coming in of around -18 to -20 dB FS (does Logic have a meter that displays both Peak and RMS values?), and are recording 24 bit, then you should be just fine.  Not every signal in a multi-track project should be touching a Peak value of 0 dB FS, in fact, you'll find your tracks sound better if you're not pounding your output bus limiter/compressor during mixdown, with all your track faders down around -15 to -25 or so.  Better to track at lower levels to preserve some headroom and dynamic range when you're mixing.

Frank Lockwood
Fireface 800, Firmware 2.77
Drivers: Win10, 3.125; Mac, 3.36

Re: Fireface 800 Loopback Volume Question

Hi thanks for the reply!  Some really good tips in there - Much appreciated.

In the end, I discovered from another post that the problem was with Logic.  The seemingly innocent 'volume control' on the transport bar, is actually a master fader, and consequently changes the output volume to whatever is being looped-back or even recorded.  Now that I know this, I intend to always leave it on 0dB, and I understand this affects bounced audio too.  It has solved both the looped-back issue, and the volume of the digital piano issue.

All I need to do now, is work out a way I can practically increase / decrease the level of my monitors on the fly, without having to flip over to TotalMix all the time.  I'm thinking about getting a control surface to do this, although I'm not sure which one, and how it would function.  If a control surface is MIDI controlled and I need it to alter faders in TotalMIx while I am using Logic, wouldn't the MIDI codes get confused and alter Logic's settings instead?  And what if I needed the control surface to alter Logic too?  Ah so many questions! smile