Headphone out from chip amp ?


2006-02-19 8:15 am
I have cannibalised many amps over the years to source components and where there has been a headphone socket, I have taken these off and kept them. Often there are a few resisitors attached to wires which were originally joined to the speaker outs.

Is is just a simple case of tapping off the speaker out for L+R +G ?

Is there a formula for the resistors to give the required Ohms (600?) for headphones.


2004-12-09 7:29 pm
Put an 8ohm resistor across between each channel hot and ground as long as your headphones have an impedance in excess of 100ohm. The resistor will be in parallel with the headphones: 8//100~ 8ohm. If your headphones are closer to 20ohm you need a resistor in the 20ohm range.

Even better use two resistors, one in series and one shunt, to create a voltage divider so as to keep the max voltage to the phones below 2V or so. The above rule of thumb for the choice of the value of the resistor to ground above now applies to the equivalent resistance of the voltage divider.

The resistors need to be 10W or more to be on the safe side.

Hope it helps.