# MobilePre USB Setup and Troubleshooting Thread



## pbc

Not sure if one of these exists, and after all the issues I've had, figured I'd start one here and hopefully save anyone else from buying a new MobilePre thinking their's was shot! 

*Equipment and Software*

This is the MobilePre I'm using...










Okay, so first things first, go download the appropriate drivers from M-Audio. I'm using Windows 7 64 Bit for the MobilePre (not the 2nd generation in my case).

http://www.m-audio.com/index.php?do...=8eb1a9920df341303f81bca7ff458be3&OS=x85#tabs

I didn't bother downloading any of the CD's provided in the box by M-Audio.

I'm also using a Dayton EMM-6 mic calibrated by CSS Labs (thanks Herb!).

http://www.cross-spectrum.com/measurement/calibrated_dayton.html

*Cables Required*

To hook up the MobilePre (run a calibration and measurements) you'll require:

2 of RCA Jack To 1/4" Mono Plug Adapter
http://www.parts-express.com/pe/showdetl.cfm?&Partnumber=090-285

1 RCA Cable, length will depend on how far your laptop is to the AVR. 15 to 25 feet is probably fine.
http://www.monoprice.com/products/p...=10218&cs_id=1021814&p_id=5348&seq=1&format=2

To hook up the Mic, you'll need a female to male XLR cable.
http://www.monoprice.com/products/p...=10244&cs_id=1024401&p_id=4753&seq=1&format=2

*Setting up the Sound Card*

Step 1: Double Click on the MobilePre icon in the bottom right corner of the Windows screen to bring up the MobilePre USB Control Panel.










Step 2: Setup the various items as shown in the pics below:

















(more on the "Latency Settings" later)


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## pbc

Step 3: Go into your Control Panel and Select "Manage Audio Devices" once you've plugged in your MobilePre and ensure you are setup as follows:


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## pbc

Step 4: Not that you've setup your cards appropriately, you'll need to launch REW and click on "Preferences". In preferences, click on Mic/Meter and select the calibration file provided with your microphone (either a specific file from CSS Labs or an averaged one from the Shack). Don't bother with the C weighted box.

Step 5: Hook up your MobilePre to run a sound card calibration. Essentially you're going to connect two of the 1/4" Mono plugs, one into the 2/R Output and one in to the Ch2 Inst/Line Input, then connect the red ends of your RCA cables one into each of the RCA to 1/4" TRS adaptor to create a loopback.

Step 6: Ensure your Channel 2 volume level is about 1/4 of the way up, Mic volume is muted and Phantom Power is OFF.

Step 7: Select the M-Audio devices for your output and input devices on the Soundcard tab of REW in the Preferences section. Check that the sweep level is between -6 and -12 db (I typically use -10db).

Step 8: Click on "Calibrate", then increase/decrease the Channel 2 volume knob on the MobilePre until you're levels for Out and In are about the same. Then click on Next, to run a sound card sweep and you should end up with a nice curve that looks like the one below. Click on "Make Calibration" and save that calibration to your hard drive.

Step 9: Disconnect the 1/4" TRS from the Ch2 Output. Remove the 1/4" Adaptor, and connect the red end of the RCA jack into the red "Aux" jack on your AVR or Processor (usually at the front of your unit). Ensure you've selected the proper Input (Aux) on your Processor/AVR. I usually use "Multichannel In" as the surround mode to ensure the subwoofer is engaged.

Step 10: If only measuring your sub at first, disconnect all your other speakers from your AVR, or alternatively, turn off your amp if you use an amp/processor combination.

Step 11: Connect the XLR cable to the Ch2 Input XLR connection on the MobilePre and the other end to your EMM-6 mic.

Step 12: Click on SPL Meter to calibrate your SPL levels. Generally I'll tape the EMM-6 mic to my Galaxy CM140 meter for most of my measuring sessions (it's just easier). Increase the volume on your processor until it reads around 75db.

Step 13: You're ready to measure. I hope!


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## pbc

*Toubleshooting*

For some reason, sometimes when you run a sound card calibration, you'll get a really "noisy" result with lines all over the place like in the attached picture.

As far as I can tell, this is possibly the result of a few things:

1. Your cables are all twisted. Try untwisting them.
2. Your AC cable from your laptop is too close to your RCA cables.
3. Your Latency (see post 1) needs to be adjusted higher or lower (note, you have to exit REW to do this).

Sometimes this keeps on persisting, and you may need to reboot. I have no idea why this happens but playing around with the above seems to make it eventually go away.

Now, when actually running measurements, sometimes you'll hear this "noise/warbling" of the tone coming out of your subwoofer. Cancel the measurement, and check all of the above again. Usually it has something to do with the cables in my experience and fiddling with them tends to make the tone go away. Sometimes you just have to keep running measurements a few times and it just suddenly works.

I know, it sounds weird, but that has been my experience (I actually bought a new MobilePre thinking my last one was shot).


*Other Items to Check*

Download the most recent version of Java ....

http://www.java.com/en/download/index.jsp


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## pbc

No idea why all these pics are showing up so many times? Was trying to get them to show up after each step instead of at the end but didn't seem to work. Maybe a mod can clean these up as I can't figure it out?


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## pbc

Anyhow, hopefully this helps people out who have the MobilePre and keeps them from spending hours (as I have) trying to figure out the various issues each time.

Hey, if anything, it will help me out next time I measure I hope! I'll update it as I encounter more issues.

If you guys are using the MobilePre and either a) notice something incorrect in the above or come across another odd issue, let me know and I'll update this thread for those.


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## pbc

Reserved


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## pbc

Reserved2


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## aackthpt

I use the same unit and the Dayton EMM-6 mic. I use the input gain at 0 rather than +12, and with the right (main/input/non-reference) channel input gain knob at the top, it puts the overall input gain into the correct range for the REW sweep. This way I almost never have to redo the SPL meter calibration in REW because I know I can just pin the knob and I am at the same input side gain as always.

I have had and fixed the warbling issue by unplugging/replugging the USB. I'm not sure if it resets the MobilePre itself or the drivers in the OS or what, but it works and I have never moved the cables around or anything when I did it.


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## pbc

BTW, is there a way to mute all the sounds coming from the computer from going to the sub?


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## EarlK

> One way ( to keep "other" sounds from reaching your subs ) ;

> If you want REW to be the only program sending sounds to your speakers ( & subs ) then don't choose the Mobile USB Pre as your default soundcard for the computer ( selected from within the soundcard control panel ) . 

> Choose the onboard soundcard for your computer ( Realtek in your case ) , as the default soundcard / then all other sounds ( non REW ) will route to the onboard soundcard ( RealTek ) .

> Hope this helps .


:sn:


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## aackthpt

pbc said:


> BTW, is there a way to mute all the sounds coming from the computer from going to the sub?


When I want to run a sweep for above the Schroeder frequency to use an ETC or whatever, I just turn my subwoofer amplifier(s) off.


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## wbz

Thanks for the step-by-step procedure. As a newb it helps. 
I have a question that you could probably help with. 
I have the new MobilePre USB which is a little different from the original one. The issue I am up against is the outputs. They are now balanced. I checked with an O-Scope and indeed they are truly balanced as the two signal pins are out of phase with the other. I need to connect one of these outputs to an unbalanced input on an amplifier. At this point I am not sure whether it is okay to plug in a TS plug, thus shorting out one pin of the output, or build an adapter that only uses one pin and references to ground. I've emailed M-Audio and have no response yet but am thinking maybe a user in this forum has already been down this road. If anyone has a schematic of this unit it could be helpful too.
Whatever the solution is it would help others if you could add an addendum to your procedures to cover the differences between the older and newer MobilePre.


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## aackthpt

I would not short output pins. I'd probably take an RCA cable, remove one end, and install a TRS on it, connecting the center conductor to either the T or R and leaving the other floating (and connecting the shield of course). You can probably buy cables and adapters to do the same thing; one of the common devices is an RCA to XLR cable used to adapt from consumer AVR output to professional equalizer or amplifier; many get this from monoprice.

You can find more information in fotto's thread about the ART USB DualPre which also has balanced ins and outs. There are also a bunch of sticky threads about connecting between pro and consumer equipment on HTS. The bottom line is you should first try direct connections, if that doesn't work in level then try something like a cheap mixer as a preamplifier (Behringer makes a unit with a street price of $35 now). You can also use something like a passive DI box (I know there are some potential issues with this but I don't really know what they are) or a powered unit like the Samson S-convert or ART CleanBox Pro, but the original CleanBox required some mods if you were looking for sub-20Hz performance as are many around here.


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## Sputter

pbc said:


> BTW, is there a way to mute all the sounds coming from the computer from going to the sub?


Steve, it seems to me I just muted the laptop card from the speaker icon on the windows taskbar. It showed both realteck and mobile-pre and I just hit mute on realteck.

I just ran into that 2 days ago but I really didn't take note what stopped it. I'm sure the above did the trick.


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## pbc

Sputter said:


> Steve, it seems to me I just muted the laptop card from the speaker icon on the windows taskbar. It showed both realteck and mobile-pre and I just hit mute on realteck.
> 
> I just ran into that 2 days ago but I really didn't take note what stopped it. I'm sure the above did the trick.


Hey Jim. I haven't had a chance to go back and redo measurements in a while, I did do a review of the PB13-Ultra as I picked up a new Sledge amp for it and quickly ran some close-mic measurements which aren't as simple as I originally thought with ported subs!

Did you end up trying to close mic your VTF-15 subs?


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## pbc

wbz said:


> Thanks for the step-by-step procedure. As a newb it helps.
> I have a question that you could probably help with.
> I have the new MobilePre USB which is a little different from the original one. The issue I am up against is the outputs. They are now balanced. I checked with an O-Scope and indeed they are truly balanced as the two signal pins are out of phase with the other. I need to connect one of these outputs to an unbalanced input on an amplifier. At this point I am not sure whether it is okay to plug in a TS plug, thus shorting out one pin of the output, or build an adapter that only uses one pin and references to ground. I've emailed M-Audio and have no response yet but am thinking maybe a user in this forum has already been down this road. If anyone has a schematic of this unit it could be helpful too.
> Whatever the solution is it would help others if you could add an addendum to your procedures to cover the differences between the older and newer MobilePre.


Thanks. Admittedly I'm hoping it helps me as much as it helps others. I cant' explain how many times I've started up REW and my MobilePre only to find some odd thing happening that I can't figure out or recall how I fixed it the last time!

Let us know if what aackthpt posted above helps...


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## wbz

Yup, pretty much confirmed what I was doing. I couldn't get much info out of M-Audio is why I posted here. Nothing like practical experience when you need help. 
I made TRS to RCA adapter. So if for any particular reason I can send opposite phase to each channel. The level drop isn't that great or a problem. 
Now I have to decide which software to stick with. I'm sampling ARTA, TrueRTA, REW, & AudioTester.
REW has the edge though as I can run it under Linux and avoid MicroSoft overhead.


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## Sputter

pbc said:


> Hey Jim. I haven't had a chance to go back and redo measurements in a while, I did do a review of the PB13-Ultra as I picked up a new Sledge amp for it and quickly ran some close-mic measurements which aren't as simple as I originally thought with ported subs!
> 
> Did you end up trying to close mic your VTF-15 subs?


Not yet Steve, since we're moving off topic i'll email you :bigsmile:


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## pbc

wbz said:


> Yup, pretty much confirmed what I was doing. I couldn't get much info out of M-Audio is why I posted here. Nothing like practical experience when you need help.
> I made TRS to RCA adapter. So if for any particular reason I can send opposite phase to each channel. The level drop isn't that great or a problem.
> Now I have to decide which software to stick with. I'm sampling ARTA, TrueRTA, REW, & AudioTester.
> REW has the edge though as I can run it under Linux and avoid MicroSoft overhead.


I had a similar experience when I thought my MobilePre was shot, i.e., their customer service left a lot to be desired. I'm not even sure I ever even received a response to my emails to their support desk!


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## pbc

pbc said:


> *Toubleshooting*
> 
> For some reason, sometimes when you run a sound card calibration, you'll get a really "noisy" result with lines all over the place like in the attached picture.
> 
> As far as I can tell, this is possibly the result of a few things:
> 
> 1. Your cables are all twisted. Try untwisting them.
> 2. Your AC cable from your laptop is too close to your RCA cables.
> 3. Your Latency (see post 1) needs to be adjusted higher or lower (note, you have to exit REW to do this).
> 
> Sometimes this keeps on persisting, and you may need to reboot. I have no idea why this happens but playing around with the above seems to make it eventually go away.
> 
> Now, when actually running measurements, sometimes you'll hear this "noise/warbling" of the tone coming out of your subwoofer. Cancel the measurement, and check all of the above again. Usually it has something to do with the cables in my experience and fiddling with them tends to make the tone go away. Sometimes you just have to keep running measurements a few times and it just suddenly works.
> 
> I know, it sounds weird, but that has been my experience (I actually bought a new MobilePre thinking my last one was shot).
> 
> 
> *Other Items to Check*
> 
> Download the most recent version of Java ....
> 
> http://www.java.com/en/download/index.jsp


Was trying to measure a Paradigm Sub2 Frequency Response last night, and this same phenomena happened when trying to recalibrate the sound card. 

Exited REW, increased the latency to 4096, went back in and all was good.

Seems to be the proper "fix" for whatever it is that is happening. At least in my case.


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## tallonskystone

hi i dont now about interfaces i just got this Mobile pre usb use off of craigslist no manual or install cd i think im set up for the most part but but i have no idea what you guys r talking aboud as for as wht REW is are a sound card calibration please inlightin me please


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## Wayne A. Pflughaupt

You must have found this thread doing a search on the Mobile Pre. Interfaces are typically used to record musical instruments or vocals to a computer.

REW is Room EQ Wizard, a free platform for taking measurements of speakers in the listening environment. It can use an interface and mic to take the measurements.

If you bought your interface to make recordings, you don’t need to worry about REW and sound card calibrations.

Regards,
Wayne


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