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Calculating PreAmp Gain in dB for accurate callibration in Raven Software
Hello,
I'm in the process of calibrating through the "step-wise" approach to my Raven Pro Sound Analysis Software to obtain measurements of my recordings accurately. I followed the guidelines and information provided by the website and community forums.
Although I have all the specifications for the microphone used as a transducer (lavalier Electret condenser microphone) and the recorder (Marantz PMD561), I have been having trouble knowing the correct PreAmp gain for the XLR microphone.
Specs for condenser microphone:
| Polar Pattern | Omni-directional |
| Frequency Range | 35-18KHz +/-3dB |
| Signal to Noise Ratio | 78dB |
| Max SPL | 120 dB |
| Output Impedance | 200 ohms |
| Sensitivity | -38dB +/-3dB / 0dB=1V/Pa, 1kHz |
| Power Requirement | 48V Phantom power |
Specs for Marantz PMD561 Recorder:
- MP3 (MPEG Layer III compression 320, 256, 192, 128, 64, or 32 kbps)WAV (16- or 24-bit linear PCM)
- Audio System
- Sampling Rate: 44.1, 48, or 96 KHz
- Channels 2 (stereo) or 1 (mono)
- Frequency Response 20 Hz - 24 kHz (+1 dB)
- Signal-to-Noise Ratio 65 dB (Mic); 85 dB (Line); IEC-A-weighted
- THD (@ 0 VU) 0.08% (Mic); 0.02% (Line)
- Dynamic Range 85 dB
- Microphone Array
- Maximum SPL: 110 dB
- Frequency range: 50Hz-20kHz
- Total Harmonic Distortion (THD): 0.30%
- Signal-To-Noise Ratio (SNR): 60 dB (A-Weighted Curve @ 1kHz)
- Inputs
- Microphone (XLR) - Sensitivity: 1.2 mVrms / 4.2kOhms
My confusion comes because there are two specifications for sensitivity, one that is strictly from the condenser microphone and another sensitivity that is given by the recorder when an XLR microphone is used as an input.
After much reading, I deducted from the specifications the use of acoustic formulas.
My deductions are as follows:
- -the microphone sensitivity is -38dB, as it appears in the microphone specifications (output).
- - The amplification gain (preamp) I calculated using the sensitivity specification under the input section of the recorder. As seen in the screenshot provided, the input sensitivity for the XLR microphone= 1.2mVrms with an impedance of 4.2kOhms. With said information, I used the Vrms=Vp/√2 to calculate the zero-to-peak voltage (Digitizers max (FS) voltage).
-I used the Gain in dB online Calculator to corroborate my calculations and obtain the value in dB for the gain.
With this information and the screenshots I attached, I wanted to ask if my calculations are correct or if the analysis of the preamp gain for the microphone and the zero-to-peak voltage for the digitizer is incorrect.
Please HELP!
-A very frustrated Grad student
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