balou
500+ Head-Fier
- Joined
- Apr 7, 2007
- Posts
- 563
- Likes
- 10
For an unbuffered design, the biasing current would have to be higher than the maximum expected output current.
let's assume a grado headphone at line-level voltage of 2v.
U = R * I
2V = 32 Ohm * I
2/32 = I
2/32 = 0.0625 A
= 62.5 mA
so the biasing current would have to be higher than 62.5mA to assure that the opamp stays class A. But this is completely impractical - thats about double the current draw of a pimeta or a mini³ (of course depending on exact config) - just for the biasing.
let's assume a grado headphone at line-level voltage of 2v.
U = R * I
2V = 32 Ohm * I
2/32 = I
2/32 = 0.0625 A
= 62.5 mA
so the biasing current would have to be higher than 62.5mA to assure that the opamp stays class A. But this is completely impractical - thats about double the current draw of a pimeta or a mini³ (of course depending on exact config) - just for the biasing.