# having trouble calibrating mobilepre USB



## coyote_5 (Mar 30, 2010)

I'm attempting to use REW with a mobilepre usb card, my op system is vista 32 bit sp2.

As far as I can tell, my laptop recognizes and connects to the sound card. When I follow the instructions for calibration setup, I get a graph a bit similar to the example of a feedback loop. If that is my issue, I'm unclear how to resolve the issue. I'm attaching a screen cap of my results along with the REW settings used.










You can see that for both input and output device I selected the mobilepre, but I don't have an option to select "line_in" for input as the REW guide suggests I should see. Not sure if this is part of the issue, or how to resolve if it is??

I'm using 3.5mm to RCA cables connected to the stereo mic input and stereo line output jacks. The red RCA jacks are connected via a f/f mono connector. Not sure what other info would be useful for anyone to help troubleshoot my issues... thanks for the help!

Edit 1:

I noticed that the "mute" box was checked in the control output section. I unchecked it to see what it would do. Here are the results - different but not what I need...

full screen:









screen with updated setting (mute not checked)


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## Wayne A. Pflughaupt (Apr 13, 2006)

> I'm using 3.5mm to RCA cables connected to the stereo mic input and stereo line output jacks.


Nope – can’t use mic inputs (not sure what you’re doing with those RCAs, this sound card doesn’t have any). Loop a cable with 1/4” plugs between the line in and line out connection (Channel 1 or 2, chose one).

Also, make sure any monitoring function is turned off.




> You can see that for both input and output device I selected the mobilepre, but I don't have an option to select "line_in" for input as the REW guide suggests I should see. Not sure if this is part of the issue, or how to resolve if it is??


What are your input options? 

What about Speaker Out? That’s what you should be using for the output, not “Line.”


Regards,
Wayne


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## coyote_5 (Mar 30, 2010)

Wayne A. Pflughaupt said:


> Nope – can’t use mic inputs (not sure what you’re doing with those RCAs, this sound card doesn’t have any). Loop a cable with 1/4” plugs between the line in and line out connection (Channel 1 or 2, chose one).
> 
> Also, make sure any monitoring function is turned off.
> 
> ...


Probably due to me trying to follow the REW guide but not fully understanding what I'm doing & why?!

I need RCAs to connect to my AVR when I actually run REW, right? No the soundcard doesn't have RCA connections, that is true, but I thought based on the REW setup guide that I should be using the 3.5mm connections on it. But it sounds like what I can do is get 1/4 adapters for the 3.5mm end of the rca cables, plug them in to the 1/4 input and outputs and then connect one channel of the 2 RCA cables together as I had before. Does that make sense?

In the getting started guide for REW, the choosing audio input and output section says: 

"Once the devices have been chosen, the input and output can be selected. Typically the input will be called "LINE_IN" and the output will be "SPEAKER" or "LINE_OUT", however these names may be different for USB soundcards - for example, the input may be labelled "Digital Audio Interface"."

So that is why I was using the line out setting. Looking at it now, when I select the Mobilepre as the output device, the only option I have for output is line out (other than the "default output" option)

Once I get the 1/4 adapters (assuming that will work?) should I be selecting speakers as the output device, and the mobilepre as the input device?


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## Wayne A. Pflughaupt (Apr 13, 2006)

> I need RCAs to connect to my AVR when I actually run REW, right? No the soundcard doesn't have RCA connections, that is true, but I thought based on the REW setup guide that I should be using the 3.5mm connections on it. But it sounds like what I can do is get 1/4 adapters for the 3.5mm end of the rca cables, plug them in to the 1/4 input and outputs and then connect one channel of the 2 RCA cables together as I had before. Does that make sense?


The Set Up guide assumes a sound card with 3.5 mm line inputs and outputs. Yours uses 1/4” line inputs and outputs, so you can ditch the 3.5 mm cable.

I assume you have some RCA cables? Just get a couple of these and you can use an RCA cable to run your sound card calibration routine. After you’ve accomplished that, you can use one of these to get the signal into both channels of your AVR. You can find these items at your local Radio Shack store.

Regards,
Wayne


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## Wayne A. Pflughaupt (Apr 13, 2006)

> "Once the devices have been chosen, the input and output can be selected. Typically the input will be called "LINE_IN" and the output will be "SPEAKER" or "LINE_OUT", however these names may be different for USB soundcards - for example, the input may be labelled "Digital Audio Interface"."


My goof - sorry 'bout that. Use the Line Out option if that's what you have.

Regards,
Wayne


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## coyote_5 (Mar 30, 2010)

thanks for the replys.

The RCAs I'm using for this are actually 3.5mm male on one end and normal RCA female on the other end, like this:

http://www.hometheatershack.com/for...s-parts-express-181-590l-stereo-rca-cable.jpg


Here are the descriptions of the output and input jacks from Mobilepre manual: 

2. Stereo Line Output Jack: This jack outputs the same signal as
the Outputs 1 & 2 jacks described below, through a 1/8” stereo jack for
easy connection to many devices such as multimedia speakers and
MiniDisc recorders.
3. Output 1 and 2 Jacks: These unbalanced 1/4” jacks output the
signal which is output from your computer and should be connected
to a pair of powered speakers, a mixer or a stereo receiver.

4. Stereo Mic Input Jack: This 1/8” stereo mini jack accepts a mic
level signal from stereo microphones with 1/8” outputs. These
microphones may be of either the stereo dynamic or self-powered
stereo condenser type. Microphone with XLR output connectors
should instead be connected to the XLR Inputs described below

1. Channel 1 Inst/Line Input Jack: This 1/4” balanced connector
accepts an instrument or line level signal for Channel 1 of the
MobilePre USB. This input is ideal for recording guitar, bass or
synthesizer. If you are recording a stereo line-level source, plug the left
channel into Line Input 1 (on the front panel of the MobilePre USB) and
the right channel into Line Input 2 (on the rear panel).

Based on the above and what you've told me, is it right to assume that I actually can use stereo line out with the 3.5mm to RCA cable, and that I just need to use the 1/4inch Channel 1 line input jack instead of the 3.5mm stereo mic jack I had been using? Then I would connect the two via F/F RCA adapter as I had been previously...

Also, in your initial advice, you mentioned to turn off any monitoring function. I'm not aware of any monitoring function, but if I bring up the mobilepre properties I do see something called Monitor Mix, see photo below:










Is that what you are talking about??

Thanks again!

.


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## Wayne A. Pflughaupt (Apr 13, 2006)

> Based on the above and what you've told me, is it right to assume that I actually can use stereo line out with the 3.5mm to RCA cable, and that I just need to use the 1/4inch Channel 1 line input jack instead of the 3.5mm stereo mic jack I had been using?


There has to be a cable looped between either the Ch. 1 line inputs and outputs, or Ch. 2, in order to accomplish the sound card calibration file. I think it would be easier to just use the 1/4” connections, but if you can figure out which one of those RCAs is which on the end of the 3.5 mm splitter, then go for it. :T




> Also, in your initial advice, you mentioned to turn off any monitoring function. I'm not aware of any monitoring function, but if I bring up the mobilepre properties I do see something called Monitor Mix, see photo below:


That may be what we’re looking for. If you get the loopback cable connected right and still have trouble generating a calibration file, try muting that.

Regards,
Wayne


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## coyote_5 (Mar 30, 2010)

well I think I've gotten a little bit farther. I'm doing the calibration with a M/M 1/4" cable running from the 2/R output to the channel 2 line in.

Here is the settings for the calibration:










I ran the calibration and it seemed to work, here is the FR graph:










The REW notes say to also check the impulse graph against examples in the help file. I can't find any examples in the help file but here is what the impulse graph looks like: Is it ok??










Then REW instructions suggest that I test that the calibration file works properly using the measurement function. I follow the instructions, but my resulting FR graph does not look like the example!!










Ideas??


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## laser188139 (Sep 19, 2009)

If I'm reading your final picture right, it does look correct. The purpose of measuring once with the soundcard file you generated is to verify that, after applying the soundcard to the measurement, the end result should be flat from end to end. Yours looks that way to me. 

You can now move on to hooking up the microphone and receiver instead of the loopback connection, loading the microphone calibration file, checking the levels, calibrating the SPL level, and taking a measurement. 

Have fun,
Bill


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## glaufman (Nov 25, 2007)

+1, but as a side note you can get a better picture of what's going on by rescaling your plot from +45 to +105 dB.


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