Stereo to Mono

[newfish]

So - I have a friend at work who only has hearing in one ear.

I'd like to make a passive device to put both channels from a stereo jack plug to one signal.

SInce he's using standard in-ear phones, I'd like to put both left and right channels of te input to both left and right channels on the output - then it doesn't matter which 'phone he sticks in his good ear.

I'm thinking this would be a simple 1/8" plug with both 'hot' connectors wired together - which then goes to both 'hot' lugs of a 1/8" socket, with a common ground.

The device will only be used with MP3 Players or PC soundcard inputs.

Would I be 'loading' the signal from the MP3 player etc by effectively shorting both signals together?

Any improvements anyone can suggest?

[arma61]

Hi

I've used one time this solution

R-channel ------/\/\/\--------|
                                         --------------------O
L-channel ------/\/\/\--------|
                                         --------------------O
GNDs    ------------------------|                 

for signal coming from a MP3 into a small mono amp made with LM383, I think I've used 2x10k

Cheers
Armando

[newfish]

Brilliant.

Thanks Armando - I'll be making said device on Friday of this week - thanks for your help.

[arma61]

Hi

glad I could help

here's a better picture of what I mean, I've checked and I've used 2x1k, I think you can adjust " to taste "



Armando

[grapefruit]

The circuit shown works fine when going into a high impedance input, but you will have mucho volume loss when going into headphones. The best way to do it is build a mono headphone amp with a summing input for L,R inputs.

If you want to do it passively ideally you would know the output drive current capacity of the headphone amp and the impedance of the headphones and select resistors appropriately.

The AKG K12 Headphones have 17 ohms rated impedance. I assume most in ear headphones are similar. I would use similar value resistors, such as 18 ohms, or a bit less like 10 ohms. It would be best to use 1/2 watt resistors. The dissipation really depends on how much level the MP3 player can output.

Regards,
Stewart.