REW Beta Release Calibration Loopback Setup Help (UMC204HD)

[garthvader]

Hi, I purchased a UMC204HD to perform basic bench diagnostics for vintage amplifier servicing instead of gathering and maintaining a bunch of old gear. However, I'm struggling right out of the gate with a simple loopback. I've attached a screenshot of my Preferences and have a single TS cable running from the interface's Main Out 2 (R) to Input 2 (R).

If set the mainout and gain2 to any values with a reasonable signal I go right into positive feedback as would be expected if the playback is feeding through. What I'm stuck on is that I can't find where to disable the input from feeding directly into the main out other than the interface's "Mix" knob. I have tried the "Mix" knob, but this also seems to cut the main output from REW; not what I want. I remember on my focusrite interface there was a way to adjust/set these things in an application they provided, but I cannot find anything similar for this Behringer. I went with the Behringer to save some money, considering its at risk on the bench , but I think its cost me more in time already .

Surely someone else has this setup.... Any help would greatly be appreciated. Thanks!

 

[John Mulcahy]

The mix knob needs to be all the way around to PB.

 

[garthvader]

Okay. Then I seem to be missing audio out. I'll play around with the mac side settings and see what I can do, maybe that's messed up. Thanks for confirming that bit.

 

[John Mulcahy]

Your soundcard preferences show the left channel as input but you said your cable was going to the right...

 

[garthvader]

Correct. The cable is on the R-out to R-in(2). I changed the REW preferences input to R and it does work, yay. I'll need to get a better interconnect . This is good, but I'm confused.

I thought this cable would be the loopback input connection (which I had set as R in that screenshot). Later I want to test something and was planning to take the main L output to amp, and voltage divided output off the dummy load to channel 1 input (L). So in my mind, the device under test would be L to L(1), and the loopback would be R to R(2). Then using REW to output L+R, I thought it would yield both signals.

Perhaps I'm overcomplicating this. I'm not sure I need to loopback etc for my tests. I just thought it would be nice to remove whatever I can of the interface and interconnects...

Thanks!

 

[John Mulcahy]

Calibration is done with the measurement output and the measurement input. If a loopback connection is to be used to provide a timing reference it goes from another output to another input.