TrueRTA Help!

[Rivers]

Folks,

I recently purchased a copy of TrueRTA, a ECM8000 mic and a used M-Audio MobilePre USB unit. I am having some trouble getting the straight line whilst doing the sound calibration. Can anyone advise me what is wrong?

I have followed the instructions, tried the loopback by using a guitar cable from channel 1 IN to channel 1 OUT but i still get really jagged lines from both samples. Tried the same with a RCA cable from stereo mic in and stereo mic out and I still get the same jagged lines.

Does anyone have any idea what I am doing wrong? I have the WAV + Master volume sliders at max, I have selected the linein for the recording options (both muted and unmuted at max volume gives the same results).

Mobilepre is set as the default device for both Input and Output.

What gives? A faulty M-audio unit?

[joetama]

If that is the curve from plugging the input directly into the output then there is something wrong. I don't have my card on this computer, but usually the sound USB sound card I use has a slight raise in the high frequency. So I just the REL "Relative" button. However, it shouldn't be jagged like that. Try a different cable or reinstalling the sound card.

I'll play around with mine to see if there is anything else I can think of.

[Rivers]

Tried 1 loopback via the guitar cable (1/4"?) and the other via the 5/32?" RCA cable already. Both produced the same kind of jagged lines.

[chasw98]

In looking at your screen shot, I would almost say that you are not getting any input or possibly output. You have the generator set for a 1000 Hz tone at -10 dbu. You should see a spike at 1K. What you are seeing just looks like noise. Try switching over to the oscilloscope mode and see if you can see a sine wave. I would try hooking the sound card up to some speakers and see if you can play music through it first. Then, second start up TrueRTA and play a tone through the speakers, then perform your loopback and see if you don't see some results on screen. Be logical about what you do and change.

Chuck

PS, it looks as if the generator is turned off. See if turning it on will give a green indicator light. Might solve the problem.

[ThomasW]

What gives? A faulty M-audio unit?

Does this look familar...



So I don't have to reinvent the wheel read this post....The text in the post under the above graph explains what you're seeing.

[Rivers]

Just gave it a try again. Tried both loopback connections with averaging set to 100, am getting this now for sound system calibration..





Chuck, I tried turning the Generator light on and it turns red, looks fine though. Picture below shows the line moving (loopback connection) with Generator turned on.

[ThomasW]

Let's see what a real plot looks linke

Do a nearfield quick sweep measurement 1" from dustcap of a woofer

[Rivers]

ummm I am a total newbie at this, but nearfield? And that's with my ECM8000 on right? ha ha.

[ocool_15]

I am thinking you don't have settings correct in the control panel. Try using a loop on the regular soundcard to see what you get.
I tried it again on my older 700mhz laptop and pink noise and quick sweeps gave me a proper response with both ends tapering off.

[StewLG]

Might not be the problem, but make sure you have direct monitor turned off

I just got the same setup working properly. One of the problems I had was a setting called Direct Monitor in the MAudio driver - it directly patches input to output, and I was getting feedback, clipping, and noise until I turned it off.

[Rivers]

Double-checked to confirm that I did not have Direct Monitor turned on. These are my settings.

[Dennis H]

Capture, mute all? Don't you need to enable an input?

[Rivers]

One post I read mentioned something about muting the capture. In any case, I tried un-muting it but it produced the same jagged results. Does anyone think I have a faulty M-Audio unit?

[ThomasW]

Have you talked into the mic to see if sound comes out your speakers?

[ThomasW]

FWIW.....

My Mobile pre software settings (not the Windows Sounds and Audio Device Properties) are
Direct Monitor Muted, link is checked
Device Output -3, link is checked, Latency Medium

Under the advanced tab Speaker settings SW Synth, CD Player and Monitor Direct are muted

My Windows Sounds and Audio Device Properties, under the Audio tab there is NO checkmark in the "Use only default devices"

BTW, you do have the Phantom power button pushed in? And where are the Mobile-pre volume control knobs set?

[---k---]

Thomas,

That is helpful information. I struggled to get my MobilPre up and running the first time. I had a lot of problems getting the volumes right. I got results that I think were accurate, but I'm not sure if I did it the best way. Getting back into it is on my list of things to do.

So what are the correct ways to set the volume on the Mobile Pre?

[ThomasW]

Ryan,

There are no 'correct' volume settings since they depend on the placement of the mic, output level at the receiver, and other variables.

If the OP wants to troubleshoot the unit he first needs to know if he has it correctly installed.

[norcad]

Like ThomasW says, the M-Audio has its own volume control panel, use it!
But dont mute USB record (You cant measure anything with recording muted?)
And you dont have to turn on the phantom power when you use an loop cable.
Set Usb record to 0, Device output -6, mute direct monitor, and adjust both volume pots on the soundcard to about 11 o'clock.
Turn on the generator, and see if you get green light(s) on the soundcard.
If not, check your settings in TrueRTA.
This is the setting I use to calibrate Speaker Workshop and Arta Software

I dont use TrueRTA, but in other SW, you must use a loop cable that connect Left out to Left AND Right in.
This because Left in will be the reference, and right in will be the actual measurment.

[Rivers]

Ok Guys, this is what I have tried.

1. Plugged in earphones via MobilePre Stereo line output. There was music when I played my mp3s.

2. Used my measuring mic (phantom power on) with Windows Sound Recorder to see if it could record, and all was fine (green signal lights up when I speak into the mic). I could re-play and hear everything through the stereo line output earphones.

3. Have tried MobilePre volume settings at 11 o'clock, 12 o'clock and 5 o'clock. I still get the same jagged lines with them, both with phantom power turned on and off.

Now I am really wondering if it is the MobilePre unit that is having an issue.

Thomas and Norcard: I tried your settings, no go still.

Thanks guys, I really appreciate the help I am getting here.

[ThomasW]

Ok Guys, this is what I have tried.

1. Plugged in earphones via MobilePre Stereo line output. There was music when I played my mp3s.

2. Used my measuring mic (phantom power on) with Windows Sound Recorder to see if it could record, and all was fine (green signal lights up when I speak into the mic). I could re-play and hear everything through the stereo line output earphones.

Now I am really wondering if it is the MobilePre unit that is having an issue.

1) and 2) tell you the Mobile-pre is operational.

Did you have TrueRTA running when you were recording through the mic? If not let's test that out.

Undo the loop-back cables. Have the mic plugged into channel #2, volume control knob ~12:00, phantom power on. Fire up TrueRTA, click on the 'Go' button. The RTA graph should start dancing around. This is the ambient noise in the room. To make things easier to see use the 1/3 octave setting. Now talk or whistle into the mic. You should see the graph rise and fall every time you talk or whistle. If the red clip light is coming on turn the channel 2 volume knob down.

BTW is the guitar cord you're using mono (single ended aka 1/4" TR) or stereo (balanced, aka 1/4" TRS)

[Rivers]

Tried speaking into the mic with TruaRTA running; the graph does rise and fall each time I speak into it.

Wow, good question on the guitar cord, believe it is a mono cord. Not sure if this is going to be of any help, I did try the loopback with the stereo line input / output instead of using the 1/4" channels but had the same jagged line effect (I can't tell if those 5/32" cords are working though, hard to test them out)

[ThomasW]

I've never used any of the stereo connections and that maybe your problem. Measurements are made with mono signals. If you measure a stereo pair of speakers use a 'Y' adapter sending the mono test signal to the L/R inputs of a stereo amp

I use 1/4" mono connectors (aka TS)



I've never used the connectors shown below




FWIW, I can duplicate your jagged squiggly line if I have the channel volume control knobs turned all the way down.

With the loop between Channel 2 in and out, and the Channel One And Two volume knob settings at any setting above off, (headphone knob position doesn't matter), and the 'R-IN' button selected at the top of the RTA window. Then go into 'Audio I/O' then click on the 'Sound system Calibration' and 'OK', I get a slightly wavey line that snaps to one that's essentially a straight line in a couple seconds.

[Rivers]

Yup, just double confirmed they are mono connectors as they only have one black ring instead of two near the tip of the connector.

With loopback on channel 2 in and out and volume at 12 o clock, I got the jagged line with both Phantom power on and off:

[ThomasW]

Phantom power is only used when a mic is plugged in, it's not used for a loop-back test

If I have one volume control turned up and the other volume control off, I can create a plot identical to yours.

If I have both volume controls at the same level setting, I get the correct loop-back plot.

[norcad]

Did you have any green lights on the Mobile Pre this time?
I noticed that you have the "Ampl" set to -10, is that correct?
If you plug in your earphones and start pink noice or a sine, do you hear anything?

[Rivers]

Tried turning phantom power off, set both volume knobs at 12 o clock, tried loopback on channel 1 and then channel 2 but still get the jagged lines.

Yup, I hear the sine through the earphones when the program does the sound calibration test.

[Rivers]

I wonder if it could be the drivers that are causing the issue. I got hold of another MobilePre box and I get the exact same results!

[ThomasW]

Are you talking about the MobilePre software drivers? I don't think so since those are the ones everyone myself included are using.

Have you contacted John Murphy? He's very responsive to email questions and he recently joined this forum so he can see the thread?

BTW have you measured any speakers yet?

[Dennis H]

Are you running Vista? Lots of people are reporting audio problems with Vista.

[Rivers]

Anyone knows what John Murphy's nick is?

Nope, am on XP.

[ThomasW]

http://www.htguide.com/forum/member.php4?u=12109

But I would contact him via his email on the TrueRTA website...

support@trueaudio.com

[john_l_murphy]

TrueRTA

Hi Folks,

Thanks to all who have offered help to Rivers regarding this problem. It is not a simple task to get a spectrum analyzer up and running and giving you good measurement results. Most electrical engineers have had the benefit of learning to use these sorts of instruments in a hands-on setting with an instructor and other engineers. So my hat is off to you who will dare to use a spectrum analyzer without much or any formal training. I've tried to make TrueRTA as friendly as possible but it is still possible to find yourself in a corner with no measurement results.

Rivers has contacted me off list about this issue. Reviewing the above it appears as if he is getting no input signal. Besides the Record Mixer setup (which appears to be good...except for the muted input) two possibilities come to mind. First, he could have a corrupt "Sound System Calibration" and if "Use Sound System Correction" is selected (at the Audio I/O menu) then all subsequent measurements will appear corrupt. So it is most important to deselect "Use Sound System Correction" before proceeding. It is also possible that he is getting no input due to a Line-In miscalibration. So to rule that out I suggested that he revert to the default calibration at the Line-In calibration dialog (at the Audio I/O menu). Finally, I suggested that he verify the signal chain with a sine wave before attempting any calibrations. Next, verify Quick Sweep and only when these tests are running smooothly should he perform a Sound System Calibration.

Hopefully this will be all he needs to start getting good measurements.

Besides my private reply to him I thought I should also reply to this thread just in case other folks are experiencing the same difficulty.

Best Regards,

John

[---k---]

John,

Thanks for the reply. Very cool to see vendors participate. :T

For future reference, what is the preferred method of receiving assistance?

[john_l_murphy]

We normally provide support for TrueRTA via email. Send your support questions to: support@trueaudio.com

Regards,

John