'headphone' mixer

[Stese]

Hey all,

I'm a newbie when it comes to audio electronics, and was wondering how I'd go about building a circuit for use as a headphone mixer.

What I want to do is take the 3.5mm jack output from a number of various sources (generally PC audio out) and mix them into a single socket for either speaker or headphone use. I'd like each line to be able to vary it's volume from a control knob, with a toggle for mute, and also for there to be a 'master' out which affects the overall volume.

these would be stereo connections, not mono.

I have a feeling it would need to be a powered device, but I'm not requiring any amplification on the output, as generally the sources are loud enough.

I'd like to ensure that the unit does not impair the quality of the audio perceptibly (I'm not an audiophile, so i'm not looking for perfect!)

Many thanks.

Steve

 

[BobK]

With all the volume controls you want, an active circuit would be best. I would use a headphone amplifier that works like an op amp (most do) and use the summing configuration. Each input would go through a pot to control the level, and the feedback resistor would be the master volume. The amp could have a small gain, like 2 to compensate for the loss caused by the pot and the input resistor.

Bob

 

[OLIVE2222]

Hi,

If volume control can be done at sources level you can mix them passively by using capacitors as it :

source 1 ---+||---}
source 2 ---+||---}----Common output
source 3 ---+||---}
.....

to be doubled for stereo, capacitor don't need to by high value for headset or small loudspeakers, 10µF to 100µF will be OK.

Olivier