How much gain do I need?
There is a troubling and constant question of microphone gain for vocal booth type recordings.
Does my microphone preamp have enough gain? How much gain do I need for (particular microphone) at (random distance.)
So, after some pondering, below is the microphone Gainstrolabe, an ancient device (this is humor) to answer this question.
This Gainstrolabe (chart) shows the amount of preamplifier gain required to target 100% on a common, 1.228V VU analog meter (at 1000Hz,) typical on analog recording gear. This with common conversational speech levels of 60dB(A) measured at one meter distance, and interpolated to more useful recording distances of one, three and six inches from the capsule.
1.228V 100% dBVU is an agreed upon standard, and although there are multiple conflicting standards for digital and digital equivalency, this 0dBVU at 1000Hz signal should result in -18dB on a dBFS digital console meter or in recording software. A common digital voice recording target.
Most microphone preamps provide at least 50dB gain, with some providing 60 and a few, 70dB. So 70dB is a realistic maximum. A few ribbon microphone preamps offer 80dB of gain, but are not computer interfaces.
Your microphone specification hopefully has something that looks like this:
18mV/Pa
Find the most similar number along the left side of this chart. To the immediate right is the amount of gain required at a few common distances.
You may have to turn mobile devices horizontally for the chart to display properly
Sens 1" 3" 6"
76.8 mV/Pa 26 35 41
68.4 mV/Pa 27 36 42
60.9 mV/Pa 28 37 43
54.3 mV/Pa 29 38 44
48.3 mV/Pa 30 39 45
43.1 mV/Pa 31 40 46
38.4 mV/Pa 32 41 47
34.2 mV/Pa 33 42 48
30.5 mV/Pa 34 43 49
27.1 mV/Pa 35 44 50
24.2 mV/Pa 36 45 51
21.5 mV/Pa 37 46 52
19.2 mV/Pa 38 47 53
17.1 mV/Pa 39 48 54
15.2 mV/Pa 40 49 55
13.6 mV/Pa 41 50 56
12.1 mV/Pa 42 51 57
10.8 mV/Pa 43 52 58
9.59 mV/Pa 44 53 59
8.55 mV/Pa 45 54 60
7.61 mV/Pa 46 55 61
6.78 mV/Pa 47 56 62
6.04 mV/Pa 48 57 63
5.38 mV/Pa 49 58 64
4.8 mV/Pa 50 59 65
4.27 mV/Pa 51 60 66
3.81 mV/Pa 52 61 67
3.39 mV/Pa 53 62 68
3.02 mV/Pa 54 63 69
2.69 mV/Pa 55 64 70
2.4 mV/Pa 56 65 71
2.14 mV/Pa 57 66 72
1.9 mV/Pa 58 67 73
1.7 mV/Pa 59 68 74
1.51 mV/Pa 60 69 75
1.35 mV/Pa 61 70 76
1.2 mV/Pa 62 71 77
1.07 mV/Pa 63 72 78
Of course, you can record with less gain than needed and try to boost later or use a lifter/booster. You would simply subtract the cloud lifter/booster gain to see the remaining requirement from the preamp. There are advantages and disadvantages of this but the booster discussion is a different subject entirely.
Your average voice level could also affect this requirement. If your normal voice is practically shouting, your gain needs will be significantly reduced.
Some common interfaces and gain estimations:
-41dB RODE AI-1
-42dB Focusrite Clarett 2PRE USB
-43dB Audient EVO 4
-44dB N I Komplete Audio 1
-44dB N I Komplete Audio 2
-44dB Audient iD44 MKII
-44dB PreSomus Studio 24c
-46dB Audient iD14
-47dB PreSonus AudioBox Go
-48dB Audient iD14 MKII
-48dB Audient iD4 MKII
-48dB Universal Audio Volt 2
-48dB Universal Audio Volt 276
-49dB TASCAM US-2x2HR
-49dB Arturia MiniFuse 1
-49dB Arturia MiniFuse 2
-49dB Focusrite Scarlett 2i2 3rd Gen
-49dB Focusrite Scarlett Solo 3rd Gen
-50dB Focusrite Scarlett 18i20 3rd Gen
-51dB Behriner U-Phoria UMC22
-52dB PreSonus Revelator io44
-52dB Behriner U-Phoria UMC404HD
-52dB Behriner U-Phoria UM2
-52dB MOTU M2
-53dB Behriner U-Phoria UMC202HD
-54dB M-Audio M-Track Solo
-54dB M-Audio M-Track Duo
-57dB Solid State Logic SSL2
-57dB M-Audio AIR 192|4
-60dB Focusrite Vocaster TWO
-65dB PreSonus Studio 26c
-72dB Lewitt Connect 6
-73dB Elgato WAVE XLR
-76dB MOTU UltraLite-mk5