Does the Apple USB-C to 3.5mm drive the Sennheiser HD 660S?

Computed from measured specifications · target SPL 110 dB · load 300 Ω

Insufficient

The Apple Apple USB-C to 3.5mm cannot drive the Sennheiser HD 660S to target SPL (~-1.4 dB headroom at 300 ohms; needs ~4.5 mW, delivers 3 mW). (Amp power at 300 ohms is estimated from its published figure at a nearby load.)

Headroom
-1.4 dB
Required (110 dB SPL)
4.5 mW
Delivered (@ 300 Ω)
3 mW *est.
Required voltage
0.99 Vrms

Power Headroom

Headroom: -1.4 dB 0 · target -1.4 dB below target marginal adequate ample -14 dB +10 +20 +36 dB

Amp delivers 3 mW at 300 Ω — short of the 4.5 mW needed to reach 110 dB SPL (-1.4 dB). Scale: -14 dB to +36 dB. Power figure estimated from an adjacent published load.

Sennheiser HD 660S Dynamic · over-ear
Impedance (rated) 150 Ω
Impedance (measured) Source: reference-audio-analyzer.pro/en/r… 216.75 Ω measured
Sensitivity (rated) 104.0 dB/mW
Sensitivity (measured) 103.45 dB/mW measured
Driver Dynamic
Spec basis Measured
Measured by Reference Audio Analyzer (https://reference-audio-analyzer.pro/en/report/hp/sennheiser-hd-660s.php) · Source ↗
Apple USB-C to 3.5mm Dongle · Single Ended
Output impedance review-measured 1.0 Ω
Power @ 32 Ω 31 mW
Power @ 300 Ω 3 mW *est.
Power @ 600 Ω 1 mW *est.
Power source Review Measured low confidence
* Loads marked "est." are derived from the published voltage ceiling at a lower-impedance load (V = √(P·R) → P_higher = V²/R_higher). All derivations are upward only.
Apple does not publish power specs. Power (31 mW @ 32 Ω) from community measurements (Kinemoss Tech review 2025). Output impedance ~1 Ω from multiple independent measurements. Derives 300 Ω and 600 Ω from voltage ceiling. Replaces synthetic 'Generic USB-C dongle' fixture. · Source ↗
Specification confidence: low

One or more amp specifications (power output or output impedance) are estimated rather than published by the manufacturer. Treat this pairing's verdict as approximate.

Power figure note

The amp's power at 300 Ω was not published directly — it was derived from the voltage ceiling at a published lower-impedance load. The actual delivered power may differ modestly.

Where to buy

Apple USB-C to 3.5mm on Amazon ↗ Sennheiser HD 660S on Amazon ↗

Disclosure: links above are Amazon affiliate links. As an Amazon Associate this site earns from qualifying purchases — at no extra cost to you. Affiliate commissions do not influence verdicts; all analysis is computed independently from the data.

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Schiit Fulla 4 Adequate 9.5 dB
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