Strange Soundcard Calibration?

[Veleric]

IMM-6 requires a TRRS headset jack, the Startech doesn't appear to have one.

John,
Ahh yes, that's correct. I didn't even think to mention that, as I've been using it so long that I forogt about that. When I was originally making measurements using only the built in soundcard on my PC, I found that I could use the imm-6 in the phones/mic combo jack by simply using a TRRS to TRS adapter cable. When doing that, the display graph on the measurement page showed the nomal increase in signal when I made measurements and did the "check levels" step before measurements.



Today I also confirmed that the imm-6/adapter combo works normally if I use the Startech interface as the output (rather than the ASUS HDMI output), and plug the imm-6/adapter into the phones/mic combo jack on the Startech. By "normally" I mean that the measurements graphic shows an increase in signal during sweeps, like this:



But if I try to use the same imm-6/adapter combo in the phones jack (L/mono) of the Startech, then the measurement graphic shows a flat line, like I showed in my previous post. And (curiously?), as I mentioned previously, it seems to give a perfectly reasonable result (SPL, IR, etc), despite the apparent "flat line" response.

Does it make sense that the adapter works fine in the built in ASUS combo jack, but differently with the Startech mic jack? Does it make sense that the measurement results (SPL, etc) with the imm-6 in the Startech mic input still look reasonable even though input graphic looks perfectly flat?

Thanks,
Eric

 

[John Mulcahy]

Does it make sense that the measurement results (SPL, etc) with the imm-6 in the Startech mic input still look reasonable even though input graphic looks perfectly flat?

No.

if I try to use the same imm-6/adapter combo in the phones jack (L/mono) of the Startech, then the measurement graphic shows a flat line

How could it work when connected to an output? How should the signal from the mic get back?

 

[Veleric]

John,
Thanks for your patience with me, I made some errors in my previous post. Typing with too much distraction and not enough rechecking!

What I meant to say is that the input graphic on the measurement page behaves as I would expect, that is, showing an increase in input signal during a sweep, if I use imm-6 with TRRS to TRS adapter plugged into the phono/mic combo jack of the ASUS for the input while using the Speaker output on the Startech.



But when I plug the the imm-6 with TRRS to TRS adapter into the MIC (Left, Mono) jack of the Startech, and using the same Speaker output on the Startech as above, then the input graphic on the measurement page behaves oddly. That is, during both the "Check Levels" and sweep measurement, the graphic displays a flat line. Yet, despite the "flat line", the Check Levels returns the "Levels OK" result. And during the sweep, the "headroom" indication changes from 99 dB to 16.7 dB (see images below). Plus, as I mentioned before, the SPL results etc are similar to what I get using either the ASUS input for the imm-6, or the umik-1 in the ASUS USB port.

The fact that the "headroom" changes during the sweep, and that a similar SPL result is obtained, seem to clearly indicate that the mic signal is reaching REW, right? And if so, why would the input graphic show a flat line?

 

[John Mulcahy]

why would the input graphic show a flat line?

Perhaps your adaptor is feeding the mic's phantom power back to the input in some way. Whatever the cause, it is not normal and I would not trust the results.