simple 2->1 mixer

[amacks]

[warning newbie question]
I'm trying to build a device that will combine 2 headphone-level stereo signals into one headphone-level output, some loss of signal strength is acceptable. Am I correct that a resistor on each of the hot legs of each of the puts will do the trick?
tia
Aaron

 

[Fenris]

A better option would be a pair of op-amps per input set in unity gain (buffers). This would prevent signal bleed-through between channels. Each of the headphone level outputs would get a buffer and then after the buffer the signals could be combined.

 

[officeboy]

I won't touch the op-amps being better, but the simple resistor trick will work.

A little more info here.
http://www.hut.fi/Misc/Electronics/circuits/linesum.html

 

[daviswe]

I like the idea of using unity-gain (or even gain controlled) buffers (amps) since the signal levels are below the power supply levels of 12V (in the application I'm considering).

Would you use a simple unity gain mixer stage after the buffers, in other words, two buffers to the non-inverting input of a single op amp? This could all be done on a 4-amp chip.

Ed