Hi. I'm using fireface 802.

For some reasons, we check the Level(checked by multimeter) from changing of Fader of TotalMix.
(We use Analog input/output balanced port no.1 in rear of fireface 802 for this test)

In free mode(no submix, TRIM, FX, EQ, Dynamics and so on. All no. Purely free I guess.
Routing target is itself. An 1/2 <-> An 1/2),

input and output of Analog port no.1 are connected directly by TRS.
(Not send the signal. Just only turn on the device)

In this environment, we set the fader from TotalMix as

H/w Inputs = 0 (gain = 0, Reference Lv = Lo Gain, Stereo)
S/w playback = 0
H/w Outputs = 0 (Reference Lv = +4dBu, Stereo)

Of course Level is very low now.

And we expect that we move H/w Input&Output Fader up slowly then Level is increasing linearly too.
(S/w Playback fader is fixed as 0. Not touch)

However, at some point, level is jump up from under the 100 mVrms to over 3~4 Vrms.
(We couldn't control the intermediate section between them)

Can we control that?(Not jump up. Linearly)
Do I miss something?

When we connect other thing to input(Generator, etc), it works right as linearly.
(Level change is linear and smooth)

Just direct connecting between input and output analog port is problem.
(Other rear ports of analog are same situation)

But it's important to us for our programming.
Please tell me anything what is the problem and how to solve this.

Win7 SP1/Fireface 802/TotalMix FX v1.5(3)

Best regards.