MOTU M2 with 250 Ω DT 990 Pro: enough, but how much is left over?
The M2 puts out 3.27 V; the DT 990 needs 2.51 V for a 110 dB peak. That leaves 2.3 dB — enough to listen, not enough to stop thinking about the volume knob on quiet recordings.
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 — with 2.3 dB in hand, which is the narrowest kind of yes.
The DT 990 Pro is specified at 96 dB/mW into 250 Ω. Converted to volts that is 102.0 dB/V, so a 110 dB peak needs V = 10^((110 − 102.0)/20) = 2.51 V. MOTU publishes +12.5 dBu for the M2 headphone output — 3.27 V — which lands at 112.3 dB, or 2.3 dB above target.
Now look at what that voltage costs in current: 2.51 V into 250 Ω is 25 mW and 10 mA. Ten milliamps. A speaker amplifier able to push several amperes can still fail here, because these headphones ask for voltage swing, not current. That is why «powerful amplifier» and «drives 250 Ω» are two unrelated statements, and why the impedance number alone predicts nothing.
If 2.3 dB is not enough. It will not be on classical or jazz mastered 10 dB below pop: you will find the knob at maximum. Lower the target to 105 dB peaks and the same output has 7.3 dB in hand — that is an honest answer too, because 110 dB is a peak, not a listening level. Otherwise you need a source that swings more than 3.27 V into 250 Ω, and no interface in this class does; that is a dedicated headphone amplifier's job.