# [EMM6/USB DualPre] - New Setup and Trouble with Input Levels / Soundcard Cal



## diffserv (Dec 3, 2011)

Hello, and thank you John for the wonderful software 

OS: Win7-64
Pre-amp: USB DualPre
Mic: Dayton EMM6

Here is my OS settings:









*1st question:* what should i have the "MIX" knob turned to on the DualPre? 'Pre-Amp', 'Computer', or half-way between?

I am attempting to calibrate soundcard. 

(originally mistyped - edited to fix)
-Loopback (RIGHT XLR IN --> RIGHT MONITOR OUT) 
-no connection(s) to LEFT INPUT or LEFT OUTPUT



Now, I have two knobs I can turn on the USB DualPre to affect the gain input in REW:
-[IN] MIC INPUT Gain (0 to +48dB)
-[OUT] Monitor Level

So, I set my levels to match REW's -12dB
Here are my settings:









Everything looks good and levels are matched -

I then run the soundcard calibration, and I get the Input error:










What is causing this? Should I be turning the MIC GAIN (INPUT) up higher, and turning the Monitor out volume lower to compensate and match levels with REW (-12dB)?

Anyways, even with the error, the soundcard response looks useable:










i remove the loopback and connect everything as follows:

LEFT INPUT --> MIC
LEFT OUTPUT --> RECEIVER
RIGHT INPUT --> LOOPBACK --> RIGHT OUTPUT

*does it matter what the gain knob is on the right input for the loopback?
*
taking a full-band measurement i am presented with the following 2 errors:



















the response looks correct overall, but I am trying to figure out how to solve the input gain issues.

*my main question is* - once i caliberate the soundcard (with my pre-amp knobs turned to match the REW input), and I supposed to keep those knobs set and not change the input MIC gain or output volume? Or can I adjust the MIC INPUT GAIN such that I stop receiving the low input errors after measuring?

Also, one other issue is my waterfall does not appear to be correct:









Any ideas?
Thank you,


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## diffserv (Dec 3, 2011)

Photos should be displayed in an hour (I just registered)


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## diffserv (Dec 3, 2011)

Ok ! Photos are working now


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## EarlK (Jan 1, 2010)

diffserv said:


> 1st question: what should i have the "MIX" knob turned to on the DualPre? 'Pre-Amp', 'Computer', or half-way between?


> In the "Computer" position .



> Everything looks good and levels are matched -
> 
> I then run the soundcard calibration, and I get the Input error:













> Re; "The Low Level Warning" flash screen .

- Instead of the 0 to 24Khz "default" sweep, try using a 5hz to 21Khz custom sweep ( implemented within the "Start & Stop" windows in the above pic ) .
- My reasoning is that flash screen warning WOULD seem to apply it's "logic" to all frequencies equally from the "start to stop of the test sweep: / therefore you need to manually "window" out the unresponsive/unobtainable frequencies that are triggering the warning ( ie; those frequencies that your pre-amp can't reproduce) . 

:sn:

btw; thanks for the pics, they are quite critical to those of us willing to offer help .:T


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## jtalden (Mar 12, 2009)

diffserv said:


> ... I am attempting to calibrate soundcard.
> 
> -Loopback (LEFT XLR IN --> LEFT MONITOR OUT)
> -no connection(s) to RIGHT INPUT or RIGHT OUTPUT
> ...


Above you indicate the loopback cable is on the *left *channel and show REW set to calibrate using the *right *channel input.

The default calibration process is to place the loopback cable on the right channel and set REW to use the right channel for input. This calibrates the right channel for measuring.

After calibration the loopback cable on the right channel is removed and mic is connected there.

[The left channel is never calibrated. The left channel can optionally be used for timing reference by placing a loopback cable there when measuring, but is technique is not used for the basic SW SPL EQ work.]


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## EarlK (Jan 1, 2010)

Good Eyes John ! :T

The OP should read  *this thread*  before trying to go much further ( or it'll be some form of;  :crying::huh::gah: :wits-end: :rant.

:sn:


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## diffserv (Dec 3, 2011)

jtalden said:


> Above you indicate the loopback cable is on the *left *channel and show REW set to calibrate using the *right *channel input.
> 
> The default calibration process is to place the loopback cable on the right channel and set REW to use the right channel for input. This calibrates the right channel for measuring.
> 
> ...


My post was in error! Sorry! (it was late!)

Soundcard cal was indeed RIGHT INPUT --> RIGHT OUTPUT LOOPBACK (no connection on LEFT input/output).

Once soundcard cal was completed, I then loopbacked LEFT INPUT/OUTPUT, and connected mic to RIGHT INPUT, and receiver to RIGHT OUTPUT.

So null issue here, but thanks for catching my error!


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## jtalden (Mar 12, 2009)

diffserv said:


> ....*my main question is* - once i caliberate the soundcard (with my pre-amp knobs turned to match the REW input), and I supposed to keep those knobs set and not change the input MIC gain or output volume? Or can I adjust the MIC INPUT GAIN such that I stop receiving the low input errors after measuring?
> 
> Any ideas?


You are getting there.

Now that the soundcard calibration is completed and the mic is connected, the soundcard input level is again adjusted so that a resonable input input level (maybe -10 to -20 dB) is obtained when the 75 dB recommended SPL level is playing. Read again the instructions for calibrating the mic as this doesn't appear to be isn't the only detail you overlooked. 

When the mic calibration is correct, check out the recommended scaling for the charts you post.


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## diffserv (Dec 3, 2011)

EarlK said:


> The OP should read  *this thread*  before trying to go much further ( or it'll be some form of;  :crying::huh::gah: :wits-end: :rant.
> 
> :sn:


:T thank you!
Changed from mono to 2ch:










As a follow-up question, *does win7 sample rate have to match room eq sample rate* (in preferences)?

I will try the modified start/stop frequency limit for sound-cal today and report back whether that removed the low level warning. THANK YOU


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## EarlK (Jan 1, 2010)

> You should make the effort to match sampling rates between Win7 & your REW preset .

> This way no funky artifacts ( from resampling ) will enter the picture .

:sn:


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## diffserv (Dec 3, 2011)

EarlK said:


> > Re; "The Low Level Warning" flash screen .
> 
> - Instead of the 0 to 24Khz "default" sweep, try using a 5hz to 21Khz custom sweep ( implemented within the "Start & Stop" windows in the above pic ) .


The problem is, there is no manual selection of the frequencies for the sound-card cal. As soon as I hit 'next', the test begins.

I can, however, manually modify the band for any subsequent frequency response testing - just not for the sound-card cal.



And I am still getting the "clipping" when performing a measurement with my mic (after sound-card cal has been completed). 










EDIT:
When measuring - the LEFT channel goes to max (clips) - which is my LOOPBACK. So I think the clipping warning is due to the left channel loopback being maxed out.










Any ideas as to why the LOOPBACK (LEFT INPUT <--> LEFT OUTPUT) is being maxed out when taking a measurement?


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## EarlK (Jan 1, 2010)

> The problem is, there is no manual selection of the frequencies for the sound-card cal. As soon as I hit 'next', the test begins.


Right, sorry about that :R, I forgot about that particular limitation of the calibration process .

Two work-arounds onder: ;

> You could reduce your sampling rate to 44.1K ( for the calibration ) which will end the HF portion of the sweep , at 22,500 hz .

> Also, you could stick to only doing a "line out to line in" calibration ( assuming your card has these inputs ) .
> FYI, typically , the line level responses of the typical SC are more linear than the mic pre-amp responses ( which I realize somewhat defeats the whole purpose of making a soundcard calibration file ) .

:sn:


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## EarlK (Jan 1, 2010)

Overload like that is indicative of either ;

(i) The input volume being set to high - or -
(ii) You have a feedback loop setup where you are sending the input back out to the output & then back into the input ,,,, & so on & so on & so on ,, creating overload . 
> This will happen when the monitor mix knob is set to output signals from the "PreAmp" section instead of the "Computer" .

> I would advise that you disconnect that loopback for the time being . 

> You need to sort out the "clipping" problem first .

> I think you'll be able to avoid clipping if you simply calibrate ( line-out to line-in ) and keep your test sweeps within a 10hz to 20Khz range .

:sn:


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## JohnM (Apr 11, 2006)

Difficult to use a ref channel loopback with the dual pre as you need a very low level on the left channel output due to the gain used for the right channel mic input. One way to achieve that can be to play with the output balance setting, but if you do not need an absolute timing reference just disconnect the loopback and tell REW (in the Analysis preferences) you are not using a loopback connection.


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## ChannelSounder (Dec 6, 2011)

Diffserv,

I am considering the ART USB Dual Preamp also, since it functions as the sound card and the XLR input with phantom power. Would you mind summarizing your final settings once you get it working, and show the audio response curve for that case? Any other details would be appreciated.
Thanks.


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## BluesSailor (Oct 9, 2011)

*UPDATE???*

Diffserv.....Any update on your set-up? What did you finally end up with and what was causing your problems?


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## diffserv (Dec 3, 2011)

*Re: UPDATE???*



BluesSailor said:


> Diffserv.....Any update on your set-up? What did you finally end up with and what was causing your problems?


Everything is functioning normally, although I am still getting clipping on the LEFT input when running measurements (the LOOPBACK connection for timing).

Freq response and even the ETC's look correct as far as I can tell.

I'm still just curious if the clipping on the LEFT input (LOOPBACK) is causing issues or not. the measurements appear to be accurate.


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