How to calibrate MobilePre for use with ECM8000?

[obijon]

I have poured over brucek's excellent REW Cabling/Connection Basics as well as many threads in this forum, but I am still a bit stumped as to the correct way to calibrate the MobilePre for use with an XLR mic.

The soundcard calibration method calls for looping the microphone input to the line output, but the MobilePre does not have an XLR output and I want to do my measurements with an ECM8000. The MobilePre has 1/8" stereo output and 1/8" stereo mic input which could be looped back for calibration, but would this be acceptible for calibrating the MobilePre since I will not be using the 1/8" jacks at all during system measurement?

Thanks!
Jon

[brucek]

The soundcard calibration method calls for looping the microphone input to the line output

No, the calibration calls for looping line-out to line-in. Even when the microphone pre-amp is integral to the device, this still holds true. The shortfall in this case would be that the mic pre-amp section of the device is not included in the soundcard file.

Experience has shown that the important and significant response drops come from the line amp portions and that the mic preamp offers very little effect.

If you're determined to use the mic-preamp portion in your loop, then you can fabricate a resistive pad (about 30dB) and loop the line-out to mic-in, but for the trouble it won't be worth it.

brucek

[obijon]

brucek wrote:

No, the calibration calls for looping line-out to line-in.

Well, I feel sheepish. I read that in the instructions several times but it failed to register.

I learned elsewhere that unbalanced outputs may be connected to balanced inputs, so I will loop the line 2 (right) output to the line 2 input using a 1/4" mono cable. After calibration I'll disconnect the loopback cable and plug in the ECM8000 to the line 2 XLR input. Am I on the right track now?

Thanks!

[brucek]

Am I on the right track now?

Yep correct, the balanced line-in jack will accept a 1/4" TS (tip/sleeve) plug and will revert to unbalanced. So, as you say, a single 1/4" TS (tip/sleeve mono) cable will be fine.

brucek