# Loopback connections by ASIO



## Peter Corp (Jan 25, 2012)

Newby with a first post here!

I only use the Line Out from my EMU 1212m card to connect to my stereo system, all inputs and outputs are by optical links to and from a Fostex D/A convertor fed by my Soundcraft Spirit SX mixer. I feed monitors and headphones from the mixer.

So, to get an accurate measurement for the soundcard calibration do I connect a loopback cable between the Line In and Line Out or should I do it via the ASIO ins and outs and the mixer?


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## JohnM (Apr 11, 2006)

The loopback connection should be from the output that feeds your system to the input that will be used to capture the mic signal (assuming an external mic pre) or a line in on the same mixer if it has a mic pre built in.


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## flatfinger (Jul 27, 2011)

The pci card has ad/ and d/a conversion that happens between the continuous audio signals of the analog world and the discreet , samples of the digital world . The loop back allows the WONDERFULL REW software to take the latency introduced by this into consideration when doing its calculations .













The 1212m doesn't have the breakout box , nor the mic preamp or the phantom power you need for most condensor- omni calibration mics that are typically used, ( I use a dayton emm6)

So by looking at the bottom card in this pic , you see 2 sets of line level , balanced TRS analog connections. so one pair will be the loop-back , and the other will be mic in and signal to the speakers amp for test signal generation ( sweept sine waves )


Probably the trickiest part is the patchmix software and getting the right in and out and assigning inserts into the strips . remember to select ASIO in the rew options ( it defaults to java ) 

If you have used patchmix extensively it should be pretty painless for you , if not , then maybe this would be a good primer ...

http://www.soundonsound.com/sos/nov05/articles/emupatchmix.htm


good luck and happy measuring:T


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## Peter Corp (Jan 25, 2012)

Do you think I should be running the calibration test through the mixer, or simply by joining an in and out cable from the external Fostex D/A convertor before they run the signal through the mixers circuits?


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## flatfinger (Jul 27, 2011)

you do want the loop back route to have the *same time domain influences* that will be contained in the mics signal path . so INFLUENCE FROM any converters that the mic's going to go through ( which are always good for a few ms latency !) should probably be in that path ( loop back) as well . use another channel of course - not a mixture of mic and Loop Back ! ....( ( yes , i know I have a propensity for stating the obvious sometimes , just want to be sure you do have separate parallel paths going there!))


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