REW Initial Setup Issues: Stuck In A Loop!

[Annie Body]

Hi
Using REW and DRC for the first time and am having some setup issues.
I have a Panasonic WM-61B electret microphone I purchased some time ago as it is almost flat between 20-20kHz. I mounted this into a microphone stand and use a low capacitance lead.
I have a PC with a Creative Soundblaster Z card with mic input and Toslink output.
I am conncting between my PC and my Cambridge Audio 851N streamer using a toslink as there is some 20 meters between them.
I can play sound from my PC to the 851N with no issues.
I first setup the SPL meter using a sound level meter and the mic connected to the PC. This is not calibrated but has been found to provide similar results when checked next to a calibrated one, so it should meet my purpose.
Calibration worked fine with my PC set to 100% sound level and the 851N to level 15 (of 30).
I then went into preferences and found the recommendation to calibrate my soundcard. That is when I have met with problems.
Further reading appears to suggest I need to calibrate my soundcard before doing the SPL level, but then the SPL level suggests calibrating the soundcard first. I can't do both!
After calibrating the SPL I find I cannot generate a sound card calibration file as it fails with too high a SPL level.
I have played with changing the PC output level, and 851N level to get the same results with less gain from the PC but I cannot seem to get it to pass.

As I am using toslink, I assume this should be fairly level between 20-20kHz as it is digital, so deduce the problem is with the microphone level settings.
If I drop the mic level to a level that passes the soundcard calibration then I can't get it to register 75dB during the SPL test.

Would someone kindly provide some assistance as to what I might be doing wrong?
Would I need to use soundcard calibration when using the toslink?
Regards and thanks

 

[John Mulcahy]

Soundcard calibration and SPL calibration are separate and not connected. Soundcard calibration is used to compensate for response roll-offs in the soundcard's analog output and input stages. It isn't really relevant when you are using a TOSLink connection to the system, though if you were determined you could use an analog output from the streamer to loop back to the soundcard input and calibrate that overall loop. If attempts to make measurements are stopping due to high SPL readings it will be because the SPL meter has not been calibrated correctly, but you can simply uncheck the "Abort above SPL limit" box on the Measure dialog.

 

[Rich Z]

FWIW, I am able to connect fine to my Denon home theater receiver using the front HDMI AUX 1 port. Only works with the Java driver in REW, however. Which means I am not really using the additional speakers. But at least I do get something.