Shure SM58 with Focusrite Scarlett Solo 4th Gen: enough gain for a quiet voice?
Twelve decibels in hand at a normal speaking level and two at a quiet one. The margin on this pair is almost entirely a property of your voice and your distance, not of the interface — ten decibels of speaking level eat ten of the twelve.
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)
Yes at a hand's distance, and only just at arm's length.
The arithmetic. The SM58 is published at −54.5 dBV/Pa, the loudest of the classic Shure dynamics. At 85 dB SPL that is −61.28 dBu; the Scarlett Solo 4th Gen clips at 14 dBu, so −18 dBFS asks for 14 − 18 + 61.28 = 57 dB out of the 69 the card publishes. Twelve decibels in hand.
The same pair, three ways of speaking:
| Source level | What it is | Gain needed | Margin | |---|---|---|---| | 94 dB SPL | close, broadcast distance | 48 dB | +21 dB | | 85 dB SPL | comfortable speaking distance | 57 dB | +12 dB | | 75 dB SPL | quiet voice, or at arm's length | 67 dB | +2 dB |
The interface never changes. The answer moves 19 dB.
On an iPad. The Solo 4th Gen is bus powered and asks 2.5 W; an iPad Air 11″ M3 supplies 7.5 W over USB-C, so the pair runs from the tablet with no powered hub. That is not true of every interface in the class — the Scarlett 2i2 4th Gen wants 4.5 W and the Audient iD4 MkII the same.
The pearl. An SM58 is a hand-held microphone, and the number in the table people quote — «SM58 needs about 50 dB» — assumes it is used as one, at a few centimetres. Put the same microphone on a desk stand 40 cm away and you are not in a different gain bracket, you are in a different product bracket: the requirement climbs from 57 dB to 67 and swallows ten of the twelve decibels the Scarlett had in hand. The cheapest fix for «my SM58 is quiet» has always been to hold it the way it was designed to be held.