Shure SM57 into a Scarlett 2i2 4th Gen: how much gain do you actually need?
Between 31 dB and 71 dB, on the same pair, depending on what you point it at. A snare leaves 38 dB unused; a quiet voice at arm's length is 2 dB out of reach. The gain question has no answer without a source level, and this page gives all three.
Signal Chain Compatibility Matrix
Select gear and parameters for live gain, impedance and SPL calculations.
Input Equipment Setup
PASS: Optimal Signal Chain
Requires minimum +60dB of clean pre-amp gain. Most budget entry interfaces max out at +50dB to +56dB and introduce hiss at max pot. An inline preamp booster (Cloudlifter CL-1 / FetHead) is strongly recommended.
The interface preamp provides sufficient headroom.
$538
$405
-25%Tonal & acoustic characteristics: Flat, wide-range frequency response for clean music and speech. Smooth, warm acoustic character with air-suspension shock isolation.
Technical advisory: With +69dB max gain, the Gen 4 Solo can drive demanding dynamics like the Shure SM7B natively without requiring an external inline booster.
Physical Interconnect Topology
Shure SM7B
Direct Cable Connection (No Intermediate Box)
1x Shielded Balanced XLR Cable (3-Pin XLR Male to XLR Female)
Focusrite Scarlett Solo (Gen 4)
Host: Apple MacBook Pro (M1/M2/M3/M4)
The pair is right for everything the SM57 is normally used for — except a quiet voice at a distance.
The arithmetic. The SM57 is published at −56 dBV/Pa, 3 dB hotter than an SM7B. The Scarlett 2i2 4th Gen clips at 16 dBu and publishes 69 dB of gain. The chain has to make up the difference between the microphone's output and 16 − 18 = −2 dBu:
| Source | Level at the capsule | Gain needed | Margin on 69 dB | |---|---|---|---| | snare drum, close | 115 dB SPL | 31 dB | +38 dB | | guitar cabinet, close | 100 dB SPL | 46 dB | +23 dB | | speech, a hand away | 85 dB SPL | 61 dB | +8 dB | | quiet voice, arm's length | 75 dB SPL | 71 dB | −2 dB |
What the top row means in practice. At 31 dB the interface preamp is near the bottom of its travel. That is not a fault — it is the range the SM57 was designed to live in, and it is why the microphone survives on snares and guitar cabinets that would flatten a condenser.
What the bottom row means. A 2 dB shortfall is a gain-staging problem, not a hardware problem: record at −20 dBFS rather than −18 and it disappears exactly.
The pearl. Shure publishes −56 dBV/Pa for the SM57 and −54.5 dBV/Pa for the SM58 — 1.5 dB apart. Whatever else separates the two microphones, gain is not it: on this interface both land the knob within a decibel and a half of the same place, and any advice that treats them as different gain problems is repeating a story rather than reading a data sheet.
A note on our own data: the catalogue entry for the SM57 carries the SM58 spec sheet as its source URL. The sensitivity we store, −56 dBV/Pa, is Shure's published SM57 figure, but the link needs correcting — flagged here rather than quietly fixed.