Doing the Two-Step
The following procedure summarizes this note for evaluating the compatibility of any microphone and any preamplifier. The sample data sheet referenced in the steps is embedded below.
Step One: Evaluating Input Overload Compatibility
1. Locate the microphone Sensitivity rating on the mic data sheet.
2. Find the Maximum SPL from the mic data sheet.
3. Using Table 1, find the microphone Sensitivity rating down the left side.
4. Find the Maximum SPL rating along the top of Table 1.
5. Move right along the Sensitivity rating row and move down the Max SPL rating column until they intersect and note the number—this is the microphone’s maximum output level expressed in dBu.
6. From the microphone preamplifier’s data sheet find the Maximum Input Level (in dBu).
7. Compare the mic’s maximum output level obtained from Table 1 against the preamp’s maximum input level obtained from its data sheet to determine compatibility.
Example Using Sample Data Sheets
1. Microphone’s Sensitivity rating is 20 mV/Pa.
2. Microphone’s Maximum SPL rating is 130 dB.
3. Table 1 shows the Sensitivity row marked 20 mV/Pa shaded.
4. Table 1 shows the Maximum SPL column for 130 dB shaded.
5. The intersecting point is at 4 dBu—this is the maximum output level of the example microphone.
6. The MS 1S Mic Stage data sheet lists the Maximum Input Level as +10 dBu.
7. Since this mic’s max output level is +4 dBu and the preamp can handle +10 dBu, then this mic will not overload this preamp (when set for minimum gain).