Purely considering power, you need to look at four specifications:
- Headphone Impedance (ohms)
- Headphone Sensitivity (dB/mW)
- Amplifier Output Voltage or Power at your headphone's impedance (V or mW)
- Amplifier Output Impedance (ohms)
1) Make sure amplifier output impedance is less than (Headphone Impedance)/8
2) Check needed power to reach desired volume. Most agree that 110dB is a painful listening level, and 115dB is thoroughly excessive. Decide the maximum volume level you expect, then insert your headphone's sensitivity into the equation or chart below.
Required Amplifier Power = 10^((Volume - Sensitivity)/10)
...or here's that equation in a convenient lookup table:
Headphone Sensitivity
db/mW) | Volume, 110 dB | Volume,
112.5 dB | Volume,
115 dB |
85 | 316.2 | 562.3 | 1000.0 |
86 | 251.2 | 446.7 | 794.3 |
87 | 199.5 | 354.8 | 631.0 |
88 | 158.5 | 281.8 | 501.2 |
89 | 125.9 | 223.9 | 398.1 |
90 | 100.0 | 177.8 | 316.2 |
91 | 79.4 | 141.3 | 251.2 |
92 | 63.1 | 112.2 | 199.5 |
93 | 50.1 | 89.1 | 158.5 |
94 | 39.8 | 70.8 | 125.9 |
95 | 31.6 | 56.2 | 100.0 |
96 | 25.1 | 44.7 | 79.4 |
97 | 20.0 | 35.5 | 63.1 |
98 | 15.8 | 28.2 | 50.1 |
99 | 12.6 | 22.4 | 39.8 |
100 | 10.0 | 17.8 | 31.6 |
101 | 7.9 | 14.1 | 25.1 |
102 | 6.3 | 11.2 | 20.0 |
103 | 5.0 | 8.9 | 15.8 |
104 | 4.0 | 7.1 | 12.6 |
105 | 3.2 | 5.6 | 10.0 |
106 | 2.5 | 4.5 | 7.9 |
107 | 2.0 | 3.5 | 6.3 |
108 | 1.6 | 2.8 | 5.0 |
109 | 1.3 | 2.2 | 4.0 |
110 | 1.0 | 1.8 | 3.2 |
111 | 0.8 | 1.4 | 2.5 |
112 | 0.6 | 1.1 | 2.0 |
113 | 0.5 | 0.9 | 1.6 |
114 | 0.4 | 0.7 | 1.3 |
115 | 0.3 | 0.6 | 1.0 |
116 | 0.3 | 0.4 | 0.8 |
117 | 0.2 | 0.4 | 0.6 |
118 | 0.2 | 0.3 | 0.5 |
An amplifier is capable of cleanly driving your headphones as long as its rated power meets or exceeds the above value
at the headphone's impedance. Obtaining output power information from a manufacturer is the challenge.