M-Audio MobilePre Soundcard Calibration

[richh]

New REW user here; please bear with me.

I have the M-Audio MobliePre connected to a vista laptop. I followed the procedure outlined in the help files to calibrate the soundcard and got a measurement graph that looked reasonable (very similar to the first sample graph in the help file). So far so good. However when I go to verify the calibration by taking a measurement with the loopback connection still in place, I get some strange results. I see the plot listed under the main graphing area with the date and time stamp and it shows it at 159dB. Probably because of this I do not see any results plotted in the main graphing area in REW. On the left hand side of REW where it shows graphs of the last few measurements I do see graph (flat line).

Any ideas as to what I am doing wrong?

[brucek]

Any ideas as to what I am doing wrong?

Yes, you forgot to run the Calibrate routine after you had set the Input and Output levels (with the loopback in place).

When yo run the Calibrate routine, you set a 'make-believe' 75dB level, so REW has some reference as to where place the results on the graph.

brucek

[richh]

Thanks for the reply. I went back into REW to try your suggestion, but before I got too far I ran into another problem... In the Settings/Soundcard/Calibration area when the 1kHz tone is playing and I am supposed to adjust the audio level control so that the input and output levels match, for some reason the knob on the MobilePre has become super sensative. When I did this same task this morning I could see the meter rise proportionally as I turned the knob. Now the meter stays black while i turn the knob until i reach a certain point and then boom, the meter is pegged. I tried both left and right channels with the same results. Do you think it's a MobilePre issue?

[brucek]

Tell me about your loopback connection/ports/cable/adapter.........

[richh]

Computer - Dell XPS M1330 notebook, running Vista SP1
REW - V4.11 build 1086
Audio Card - M-Audio MobliePre PID/Ver 200F, V1.03 firmware

MobilePre to notebook connected via USB cable

Loopback connection 10' 1/4" guitar cable, parts express part number 241-327

What I did.

- Plugged in MobilePre into laptop, turned on the phantom power, turned the channel 1, 2 and headphones control knobs all the way down.
- started REW on laptop
- go into settings/soundcard
- sample rate set at 44.1kHz
- change output device and output to line 1/2 (MobilePre) with default output
- change input device and input to Line 1/2 (mobilePre) with default output (greyed box so it cant be changed)
- input channel set to left
- click on measure
- using guitar cable, plug one end into ch1 inst/line jack on front of mobilepre the other end into 1/L output jack on back
- click next
- change sweep level to -10 dB FS (other settings are wave vol is at 1, output vol is .01, replay buffer 32K, input vol .25, record buffer 32K) I also should note that the wave vol, output vol, and input vol are greyed out.
- click next
- out meter on REW jumps to about -10
- slowly tun the channel 1 knob on the front of the mobilepre to try and match levels. signal led on mobile pre is off. i start with the knob at about 7:00, nothing happens on the meter until i get to about 11:00. then the mobilepre signal led starts to flicker green. i turn a little more and the meter shoots up all the way to the top and the clip led on the mobilepre also turns on.

As I mentioned before, this morning when I did the same procedure I was able to match the levels very easily. Not sure what has changed.

[brucek]

turned on the phantom power

?? This is to power the microphone. Why turn it on?

default output

Why default and not the card as the selection?

running Vista SP1

Are you able to adjust levels using Vista Recording and Playback Devices tabs?

brucek

[thebuffman]

richh wrote:

Thanks for the reply. I went back into REW to try your suggestion, but before I got too far I ran into another problem... In the Settings/Soundcard/Calibration area when the 1kHz tone is playing and I am supposed to adjust the audio level control so that the input and output levels match, for some reason the knob on the MobilePre has become super sensative. When I did this same task this morning I could see the meter rise proportionally as I turned the knob. Now the meter stays black while i turn the knob until i reach a certain point and then boom, the meter is pegged. I tried both left and right channels with the same results. Do you think it's a MobilePre issue?

wow richh i am having this same exact issue. i am performing loopback on my left channel. btw i am using a m-audio fast track pro not the pre. i have a 1/4" adapter plugged into the front (mic input) and into the back (TRS #1 output). When I run the loopback test, the decibels stay in the 60's to 70's while i am upping the gain on the channel and then once i get to about 3o'clock position...BOOM CLIP!...straight red . i am going to try turning down the volume in the operating system volume control to see if this helps.

i will let you know.

[thebuffman]

okay i got it for you man

on the pro version there is a "Mix" and an "Output" control. these controls are totally separate from the channel controls. originally i had the mix control set all the way counter-clockwise. to fix the issue i set the mix control to 12 o'clock and while setting it i noticed that this control added more stability to the signal. the signal began crawling toward 0 at a nice gradual pace. i then set the "output" control to 12 o'clock. after setting these two controls, i was able set my channel control to -12 and it was a nice gradual control. hope that helps.

here is a description of the controls. if someone can explain why changing these fixed the problem i would much obliged. i really want to understand this stuff and not just operate it :
Input/Playback Mix Level Knob (Mix IN, PB) – This knob controls the audio mix sent to the Line Outputs, fading between the
input signals (input monitoring) and the output signal from your audio application software. When turned fully counter-clockwise
(IN position), only the input signals are heard at the line outputs. When turned fully clockwise (PB position), only the output signal
from your DAW software is heard at the line outputs.

Output Level Knob (Output Level) – This knob controls the signal level at the line outputs. This control is independent from the
Level knob.

[brucek]

originally i had the mix control set all the way counter-clockwise

Mix is a monitor control. REW requires all monitors are shut off.

brucek

[thebuffman]

brucek wrote:

Mix is a monitor control. REW requires all monitors are shut off.

brucek

interesting then because there is no shut-off button for this control. perhaps setting the dial to 12o'clock puts it at this state