HD 560S on a Pixel 10: the spec sheet answers this one without arithmetic
Sennheiser rates the HD 560S at 110 dB for 1 Vrms, so a 110 dB peak needs exactly 1.000 V. A $76 KA13 delivers 1.203 V into 120 Ω: 111.6 dB, 1.6 dB of headroom — enough, with nothing to spare.
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, by 1.6 dB. Enough to listen, not enough to stop watching the volume on a quiet recording.
The HD 560S is 120 Ω and 110 dB at 1 Vrms. Since the target here is a 110 dB peak, the required voltage is exactly 1.000 V — the datasheet is the answer, and the formula V = 10^((110 − 110)/20) = 1 V only confirms it. That costs 8.33 mW and 8.33 mA. The FiiO KA13 on phone power makes 1.22 V; its <1.7 Ω output takes a share of the 120 Ω load, leaving 1.203 V, which is 111.6 dB SPL.
The pearl: this is what a per-volt sensitivity is for. Manufacturers who publish dB/mW force a conversion — S_V = S_mW + 10·lg(1000/Z) — and that conversion is where most amateur calculations go wrong, because at 32 Ω it adds 15 dB and at 300 Ω only 5. Sennheiser, AKG and Sony's MDR-MV1 sheet each pick one convention and state it; beyerdynamic's classic DT sheets state neither. When a spec sheet says «110 dB (1 kHz, 1 Vrms)», the volt figure is directly comparable with the volt figure of any source, and the whole question becomes one subtraction.
A step up costs one decibel of nothing. The KA17 at 2 V delivers 1.983 V into the same load: 115.9 dB, 5.9 dB of headroom instead of 1.6. Whether that is worth twice the price depends entirely on how quiet your quietest recording is — 1.6 dB of headroom is not a defect, it is a warning that the control will spend its life near the top.
Two things about the phone. Google lists «USB Type-C 3.2» under ports and stops there — no current, no generation — so the 4.5 W recorded in this catalogue is derived from the USB Type-C Default level for a single-lane USB 3.2 port (900 mA at 5 V) and should be read as a floor. And the cable in the box is USB 2.0 by Google's own spec sheet: it carries power and audio perfectly well, but it is not the cable to trust when a data-rate problem is being diagnosed.
Damping: verifiable and comfortable. 120 Ω against FiiO's published <1.7 Ω is a ratio of 70.6, far past the 8 the 1/8 rule wants. Nothing here is bending the frequency response — the only tight number is the headroom.