• gvr
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  • Registered: 2012-05-19
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Topic: Gain for input channel 9/10 using ASIO drivers

Hi there,

Background:
I've connected an Earthworks M30 (sensitivity: 31mV/Pa) to a Fireface UFX on input channel 9. I interface with it using ASIO drivers. I need to get absolute data on sound pressure, so I need to setup UFX for the measurement program I use (ARTA).

Questions:
a) When I read the M30 signal using the ASIO driver, what gain has been applied to it - if any? The default value here is 1 (unaltered).
b) What is the maximum input voltage?

My measurement software needs both these values. Why it needs #a is pretty clear since it couldn't estimate pressure without it, but I'm not quite sure why it needs #b.

Thanks!

  • From: Germany
  • Registered: 2007-04-10
  • Posts: 9,783

Re: Gain for input channel 9/10 using ASIO drivers

The first question does not make much sense, and gain is not related to ASIO.... You would need a signal of a known absolute volume to help the software determine where it's at, I guess... Or does it generate its own signals?
The value for input level is in the manual...

Regards,
Daniel Fuchs
RME

Regards
Daniel Fuchs
RME

RME Support's Website

  • Registered: 2010-11-29
  • Posts: 1

Re: Gain for input channel 9/10 using ASIO drivers

I also use the same combination of Earthworks M30 + UFX & ARTA.  I don't bother attempting to set the gain manually, as I use an acoustic calibrator that fits snugly over the mic and puts out 92DB.  The diameter of the M30 is the same as most contemporary measurement mics so the calibrator fits.  Calibrators are pretty freely available and at modest cost as accessories for sound level meters (try FleeBay).  Way more accurate and easy to use.

RogerD

  • gvr
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Re: Gain for input channel 9/10 using ASIO drivers

Thanks for the tip! Which calibrator do you use? Did you experience any difference in gain between the left and right channels? I got 4.5db which seems like a lot.

  • From: Germany
  • Registered: 2007-04-10
  • Posts: 9,783

Re: Gain for input channel 9/10 using ASIO drivers

Are you sure the difference is in the actual gain, not the microphones? Have you flipped the mics around?


Regards
Daniel Fuchs
RME

Regards
Daniel Fuchs
RME

RME Support's Website

6 Reply by gvr (edited by gvr 2012-10-02 05:15:14)

  • gvr
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Re: Gain for input channel 9/10 using ASIO drivers

Hi Daniel,

Thanks for a great product, and your fast support! I just moved the same mic from one input to the other while running a static sine wave through a speaker, so it's not the mic.

Regarding the original question, I have a calibrated ($650 Earthworks M30) mic with a sensitivity of 30mV/Pa, and I'd like to use it to measure SPL. It would be really great if you could explain how to determine the voltage level of the mic input. I know that 30mV is equal to 1Pa, so if I could just determine the voltage of the Mic input somehow, I could use that as a reference point.

There are two other ways to do this:
a) Strip the XLR cable open and use a digital multimeter to measure the RMS voltage right off the cable (this is what I did, it's a bit of a pain but it works)
b) Use an acoustic calibrator (this is what the guy above did, it is easier but requires you to buy a $300 acoustic calibrator)

The best would be if one could use the UFX to determine the mic voltage.

Cheers and thanks,
Marcus

7 Reply by MC

  • MC
  • MC
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  • From: Germany/Thailand
  • Registered: 2007-04-06
  • Posts: 25,604

Re: Gain for input channel 9/10 using ASIO drivers

You can. The specs are in the manual.

Regards
Matthias Carstens
RME

MC's Website

  • From: Germany
  • Registered: 2007-04-10
  • Posts: 9,783

Re: Gain for input channel 9/10 using ASIO drivers

And this will help with any conversions you might need:
http://www.sengpielaudio.com/Calculations03.htm

Regards,
Daniel Fuchs
RME

Regards
Daniel Fuchs
RME

RME Support's Website

  • gvr
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  • Registered: 2012-05-19
  • Posts: 10

Re: Gain for input channel 9/10 using ASIO drivers

Hi Guys,

Ok I think I got it:
- Gain 0 dB = +12dBu
- Gain 65 dB = -53dBu

So, 0.031v RMS = -28dBu, which should mean that if I read 0dBFS with the gain set to 40 dB I should be bang on.

Best,
Marcus