Loopback output not producing an output MacOS

[bobkatz]

First of all, congratulations to John for constantly maturing REW. Continues to blow my mind!

I've been using REW for Windows for years for both capture and analysis. I've been using REW on MacOS for analysis of existing .mdat files, but up to now, I haven't used MacOS for capture. But in March I have to align a system on location with my MacBook Pro (M3 Mac). So I decided to test my Prism Lyra Interface with REW version 5.30.8 to ensure I have a full setup for capture.

Problem: I can't get the loopback output to feed any of the Prism's outputs. Nothing shows in response to any loopback output choice on the Prism control app's meters. I would expect to see two simultaneous signals in the Prism App, the main output and the loopback output, but I can't. I've tried all the Prism outputs and it appears that REW is not feeding anything out of the loopback output.

Would be nice to figure this out. I tried downgrading to REW 5.30.5 and also downgrading the Prism Firmware to firmware that I know has worked for me in the past on PC, but it didn't help.

Here's a screenshot of the setup that I'm trying to get to work. Lyra hardware output 5 is Toslink left channel. Lyra output 2 is an analog output that I want to use for loopback. Lyra Input 1 is the microphone. Lyra input 2 is an analog input used for loopback return. I have an external jumper between Lyra output 2 and Lyra input 2.

Fortunately I have a workaround: The monitor system I am aligning requires a Toslink input. I don't care if I don't measure accurate time of flight, I just want a consistent timing reference. So, since the Prism "mults" its coax and toslink outputs, I just fed the coax output to the coax input and that's my loopback signal.

 

[John Mulcahy]

Have you selected Use loopback as timing reference on the Measure dialog?

The loopback output gets the sweep signal when making a measurement with the timing reference mode set to one of the loopback options. To routinely echo the generator output to the loopback output select the option highlighted below on the generator:

 

[bobkatz]

Have you selected Use loopback as timing reference on the Measure dialog?

View attachment 68138


The loopback output gets the sweep signal when making a measurement with the timing reference mode set to one of the loopback options. To routinely echo the generator output to the loopback output select the option highlighted below on the generator:

View attachment 68135

 

[bobkatz]

Hi, John. Thank you. I did have loopback set as timing reference in measure. Turns out the problem was in the Prism interface. I downgraded the firmware and the loopback problem was not fixed. Then on a whim I upgraded the firmware back to current, and the loopback started working! I think the new firmware didn't stick the first time :-(