Can be directly connected to CD players, tuners and tape recorders.
Tested with several headphone models of different impedance: 32, 100, 245, 300, 600 & 2000 Ohms.
Schematic shows left channel only.
B1, SW1, J1 & C3 are common to both channels.
R3 value was calculated for headphone impedance up to 300 Ohms. Using 600 Ohms loads or higher, change R3 value to 100K.
Current drain: 35mA per channel with 32 Ohms impedance headphones. Much less with higher impedance loads
Output voltage: Above 2V peak-to-peak on all loads
Sensitivity: 90mV RMS input for 2V peak-to-peak output
Frequency response: Flat from 30Hz