Motu M4 calibration In/Out mismatch in REW

[lizhuoyin]

While waiting for cables/connectors to hook up M4 to speakers, I am doing some measurements.

First, I tried to calibrate M4.
I connect LINE OUT 3 to LINE IN 3 at back.
You can see the In is not the same level as Out in the following picture.
Also M4 IN/OUT meters (LED screen) are not at the same level either.

It looks like there is an attenuator in M4 LINE IN 3/4 to reduce input level by 3.8dB.

Is it normal?

If I change Input to front IN 1, In and Out will be the same at -12.0 both in REW and on M4 meter screen.

 

[artburda]

It‘s normal. The output is 16 dBu and the line inputs 3/4 are 18 dBu. Inputs 1/2 with TRS are 16 dBu max and XLR 10 dBu. RTFM ;-)