Does the Bottlehead Crack 1.1 drive the Beyerdynamic DT 770 Pro 250?

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

Adequate OTL-compatible pairing

The Bottlehead Crack 1.1 adequately drives the Beyerdynamic DT 770 Pro 250 with limited margin (~9.7 dB headroom at 300 ohms; needs ~35.9 mW, delivers 333 mW). This OTL tube amp suits the headphone's impedance (255 Ω) — a classically compatible pairing for high-output-impedance tube sources.

Headroom
9.7 dB
Required (110 dB SPL)
35.9 mW
Delivered (@ 300 Ω)
333 mW
Required voltage
3.02 Vrms

Power Headroom

Headroom: 9.7 dB 0 · target 9.7 dB below target marginal adequate ample -14 dB +10 +20 +36 dB

Scale shows dB headroom above the 35.9 mW required to reach 110 dB SPL. Amp delivers 333 mW at 300 Ω (+9.7 dB above target).

Beyerdynamic DT 770 Pro 250 Dynamic · over-ear
Impedance (rated) 250 Ω
Impedance (measured) Source: reference-audio-analyzer.pro/en/r… 254.6 Ω measured
Sensitivity (rated) 96.0 dB/mW
Sensitivity (measured) 94.45 dB/mW measured
Driver Dynamic
Spec basis Measured
Measured by Reference Audio Analyzer (https://reference-audio-analyzer.pro/en/report/hp/beyerdynamic-dt-770-pro-250.php) · Source ↗
Bottlehead Crack 1.1 Desktop Tube · Single Ended
Output impedance manufacturer 120.0 Ω
Power @ 300 Ω 333 mW
Power @ 600 Ω 166 mW *est.
Power source Manufacturer
* 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.
Bottlehead product page (bottlehead.com/products/crack-1-1-otl-headphone-amplifier-kit): output impedance 120 Ω (published). Power: '~10V into a 300 ohm load' → P = 10²/300 = 333 mW; the '~' qualifier makes this approximate. 600 Ω derived from 300 Ω voltage ceiling (~10 V). Designed for 300–600 Ω headphones only. · Source ↗
Impedance compatibility

This OTL tube amp's high output impedance (120 Ω) is a good match for the Beyerdynamic DT 770 Pro 250's 254 Ω impedance. The impedance ratio (2.1×) falls within the recommended range for high-output-impedance tube sources — a classically well-matched pairing.

Where to buy

Bottlehead Crack 1.1 on Amazon ↗ Beyerdynamic DT 770 Pro 250 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.

AmplifierHeadroom
Schiit Lyr 3 Ample 14.0 dB
Schiit Valhalla 2 Ample 13.5 dB
Topping L30 Adequate 8.9 dB
Topping A90 Adequate 8.4 dB
iFi Zen DAC V2 Marginal 0.0 dB
Apple USB-C to 3.5mm Insufficient -10.4 dB

See all amplifiers for the Beyerdynamic DT 770 Pro 250 →

HeadphoneHeadroom
Koss Porta Pro Ample 20.8 dB
Grado SR80x Ample 20.5 dB
Focal Clear (original) Ample 15.3 dB
Audio-Technica ATH-AD700X Ample 15.2 dB
AKG K240 Studio Adequate 6.2 dB
Fostex T50RP Mk3 Adequate 4.3 dB

See all headphones for the Bottlehead Crack 1.1 →