M-Audio Mobile Pre -- calibration ? - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 16 Old 01-24-07, 10:24 PM Thread Starter
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Re: M-Audio Mobile Pre -- calibration ?

Next time I order from Parts Express, I'll get a stereo 1/4" phono and make an XLR to balanced phono cable (still have plenty of cable and XLR connectors) and compare the calibration files. Sadly that will be a couple of weeks, but I'll be sure to put that on the order.
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post #12 of 16 Old 01-24-07, 11:02 PM
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Re: M-Audio Mobile Pre -- calibration ?

The Mobile Pre USB does not have balanced outputs.

So it would seem that the best we can do to calibrate this device is to go unbalanced out to unbalanced in.

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post #13 of 16 Old 03-31-14, 03:39 PM
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Question Re: M-Audio Mobile Pre -- calibration ?

Greetings from the SW Colorado mountains. As intro, I'm perhaps a fairly advanced car guy but with little car audio experience. I've been learning what I can to update/modify/tune a car audio system I built over the winter and I've made some good progress. I believe there is more on the table.

Hanatsu in DIYMA has been super helpful and suggested I try REW instead of TRTA so that's why I'm here.

I've searched HTS and so far found 3 threads that mention M-Audio MobilePre USB (the earlier 1.1 model) and some reference to setup.

Regarding my question: This thread came the closest so I'm bump-starting it again although it is a very old thread.

I've been using a Dayton Audio EMM-6 mic with this USB preamp with TrueRTA v4. The loopback I've been using for sound card calibration was an adapter cable from 1/8" stereo line out to 1/4" phono mono "Ch1 inst/line in". In TRTA, when testing the cal, I get a repeatable corrected nice flat line with that calibration and loop, but as people have aptly mentioned in this thread, that is with phantom power off and that path is NOT going through the XLR jack.

Furthermore, in REW, I continue to get an error message when trying to calibrate saying that more than 12db correction is necessary so it isn't a valid calibration. When saying ok and overriding that, making/saving the cal and testing - the test sweep is initially nice and flat but then shows a sharp roll upward from 1.5k to 20k.

It doesn't appear to me that there was a clear consensus in this thread on best loopback connection. So with the above context, I hope someone can help with this question:

Has anyone used this USB preamp and found an accurate way to loop it and calibrate it for REW?

Thank you,


edit: I tried using a 1/8" patch cable between the 1/8" stereo line out and 1/8" stereo mic in. It required turning the preamp's gain knob down very low, but I obtained what acts like a valid calibration with no error message. When testing that cal, it makes a very flat line.

I believe I'll try to find an adapter patch cable for 1/4" phono mono to XLR and see if I can get a similarly reliable cal there with very low gain. I have my doubts about whether that will work with phantom power on or not.. and is such a cable even available? Amazoning it now.

Last edited by MustangMichael; 03-31-14 at 04:28 PM.
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post #14 of 16 Old 04-01-14, 06:01 AM
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Re: M-Audio Mobile Pre -- calibration ?

You'll see that you're trying to talk to ghosts // discovered by clicking on the previous posters names & then looking at the info available under those posters "User's Profile" .

Buy a 1/4"mono to XLR cable and calibrate the mic pre-amp ( of your choice ) .

That cable type is available from many sources .

Keep phantom power turned "off", during this procedure .

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post #15 of 16 Old 04-01-14, 11:26 AM
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Thumbs up Re: M-Audio Mobile Pre -- calibration ?

EarlK wrote: View Post
You'll see that you're trying to talk to ghosts // discovered by clicking on the previous posters names & then looking at the info available under those posters "User's Profile" .

Buy a 1/4"mono to XLR cable and calibrate the mic pre-amp ( of your choice ) .

That cable type is available from many sources .

Keep phantom power turned "off", during this procedure .

Earl, thank you for your input. I appreciate it. I found mostly super long cables in that build but also found a mono 1/4 to XLR adapter so I can use one of my existing short XLR cables and plug it into one of the 1/4" jacks.

After such calibration, I'm assuming I would then need to use the same 1/4" jack (with adapter to 1/8") as the output to the car stereo head unit..

(FWIW: I read in feedback somewhere that monoprice sells such cables but that the pinout is not right on this cable type from that maker.)

With an ancient thread, I figured it was a shot in the dark. Thanks again,


Last edited by MustangMichael; 04-01-14 at 11:33 AM.
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post #16 of 16 Old 04-07-14, 02:00 PM
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Smile Re: M-Audio Mobile Pre -- calibration ?

I doubt many people are still using M-Audio MobilePre USB v1.1 , but here is some info in case anyone else stumbles across this old thread as I did.

I had some software problems so I had to use TRTA to test. With thanks to EarlK, looping the MobilePre (v1.1) with a 1/4 to XLR cable (1/4 mono line out to XLR with phantom power OFF) easily makes a good, totally repeatable flat hardware calibration. If you've used this model of old preamp, you may already have seen that - depending upon other settings - XLR jack's mic gain control may have to be at or a bit under one quarter of control's scale or noise will prevent repeatable calibrations.

To output for actual RTA work, I planned to use a 1/4 mono adapter to 1/8 stereo. So I thought to try to double check output method a couple of ways. First was: Using the same line out 1/4 jack with an adapter to 1/8 stereo and plugging into the stereo 1/8 mic input; still tests very flat with maybe a slight 1/4db bulge in the lower freqs and flat everywhere else.

I tried 1/8 stereo line out to 1/8 stereo mic line in and found gradual 1.5db upward sweep from 80hz down. Probably not a big deal and may be close enough for people like me. Even so, it was much less deviation than when first testing without calibration.

Anyway, for my uses, it appears I'll use the 1/4 line out to XLR in calibration with phantom power off. Then for RTA testing after the loop is removed, I'll use 1/4 mono jack out adapted to stereo 1/8 to the head unit's stereo 1/8 aux input.

I can't prove if any of the above is accurate with phantom power ON. All testing was done with phantom power OFF. So that's as far as I can confirm it.

Thanks again, Earl. Looks like it's on for some more RTA work.


edit: I (finally) found my 1/4 to 1/4 cable and connected the same line out jack to the 1/4 line in next to the XLR jack. With the same quarter to XLR hardware calibration, the quarter quarter cable shows a perfectly flat curve just like the cal curve. FWIW, with this mic preamp, quarter/quarter cable may be close enough.

Last edited by MustangMichael; 04-07-14 at 06:58 PM. Reason: Update re cabling
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calibration , maudio , mobile , pre

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