soundcard calibration for MOTU M4 - Why is there a difference between In and Out?

[lizhuoyin]

LINE OUT 4 is connected to LINE IN 3 thru a balanced TRS cable.

I don't understand why there is a 3.82dBFS diff between Out and In. in REW here.

 

[sm52]

The output level and the input level can be adjusted. If you make loopback at input 3, then point it where Loopback input. If you are measuring not a subwoofer, select at 'Levels' 'use main speaker'.

 

[lizhuoyin]

The output level and the input level can be adjusted. If you make loopback at input 3, then point it where Loopback input. If you are measuring not a subwoofer, select at 'Levels' 'use main speaker'.

Thanks for your reply.
In ASIO mode, I could not adjust output and input level. If I switch to Java, I can adjust levels but can only decrease the levels (max at 1) which will not help since I want to bring the IN up to the same level as OUT.

I am trying to do the loopback tests. I thought the first picture is the correct setup. I tried set Loopback Input, but IN 3 is disabled in the first picture. Have no idea how to do it.

 

[sm52]

In ASIO mode, I could not adjust output and input level.

write to Motu support about it. It should not be. Or you haven't installed some their drivers.

 

[John Mulcahy]

If you are planning to use a different input for measurement (e.g. Input 1 or 2) that's the one that should be used for the loopback. Interfaces may not have the same input and output sensitivity, so the gain difference may be normal. If the Motu comes with a mixer app you may be able to adjust gains there.

 

[lizhuoyin]

If you are planning to use a different input for measurement (e.g. Input 1 or 2) that's the one that should be used for the loopback. Interfaces may not have the same input and output sensitivity, so the gain difference may be normal. If the Motu comes with a mixer app you may be able to adjust gains there.

That's most likely the case. Thank you very much, John. Great tool too.

 

[mlloyd1]

lizhuoyin:

what did you end up doing?
i experienced this on my new M4. i wanted to use input/output 3 or input/output 4 but both had this same discrepancy.
however, if i use the front 1 or 2 line input and leave the gain knob at lowest setting, the levels are the same using 3 or 4 as line outputs. so until i understand why and what to do to fix it, i always use front line 1 as input and rear line 3 as output for measurement applications.