The Abyss AB-1266 Phi TC is 50Ω at 88.0 dB/mW; the Beyerdynamic DT 770 Pro (80Ω) is 80Ω at 96.0 dB (no reference unit printed). This page is only about what they ask of an amplifier — not how they sound, which no specification on either sheet can tell you.
The Abyss AB-1266 Phi TC needs 8.0 dB more than the Beyerdynamic DT 770 Pro (80Ω) to reach the same loudness — 16 mW against 2.5 mW.
| Specification | Abyss AB-1266 Phi TC | Beyerdynamic DT 770 Pro (80Ω) |
|---|---|---|
| Impedance | 50 Ω | 80 Ω |
| Sensitivity | 88.0 dB/mW | 96.0 dB |
| Sensitivity (voltage) | 101.0 dB/V | 107.0 dB/V |
| Power for 100 dB | 16 mW | 2.5 mW |
| Voltage for 100 dB | 0.89 V | 0.45 V |
| Current for 100 dB | 17.8 mA | 5.6 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 6.25 Ω | 10.00 Ω |
| Sources that reach 100 dB out of 280 | 275 | 280 |
One caution before reading the rows. Beyerdynamic DT 770 Pro (80Ω) printed a decibel figure with no reference unit, so this page reads it as per milliwatt. If it is really per volt, that model needs far more than the table says. Why the two readings differ by so much.
5 of the 280 sources have the power for the Beyerdynamic DT 770 Pro (80Ω) but not for the Abyss AB-1266 Phi TC — Apple USB-C dongle (EU), Zoom AMS-22, Steinberg UR22C, 2 more.
9 sources are low enough in output impedance for the Beyerdynamic DT 770 Pro (80Ω) under the one-eighth rule but not for the Abyss AB-1266 Phi TC (Zoom AMS-22, Arturia MiniFuse 2, Arturia MiniFuse 1, 6 more).
275 of the 280 sources here reach 100 dB on both. That count is about power only — the output-impedance and hiss lines above are separate questions, and a source can pass this one and fail those.
Each model has a page of its own with the full source list, the hiss estimate and the provenance of every figure above: Abyss AB-1266 Phi TC and Beyerdynamic DT 770 Pro (80Ω). Each figure on this page is labelled on those pages with where it came from, including the ones Abyss and Beyerdynamic never published — what Abyss publishes and what Beyerdynamic publishes, both counted.