# Stereo to 2-channel mono question

Discussion in 'Electronic Basics' started by JK, Aug 9, 2011.

1. ### JKGuest

I posted this last week in sci.electronics.design but got no responses.
Probably it's too basic. Anyway...

I'd like to make a small male/female patch-cord that would passively
mix-down stereo headphone output to two-channel mono.

Assuming typical MP3 player drive levels, is this circuit OK?

Plug > -- to -- > Jack
~~~~ ~~~~
Left __[R1]___.__.__ Left
Right __[R2]___| |__ Right
Common _______________ Common

R1 = R2 = 1000 ohms

Thanks for any advice!

..

2. ### Tom BiasiGuest

"JK" wrote in message
I posted this last week in sci.electronics.design but got no responses.
Probably it's too basic. Anyway...

I'd like to make a small male/female patch-cord that would passively
mix-down stereo headphone output to two-channel mono.

Assuming typical MP3 player drive levels, is this circuit OK?

Plug > -- to -- > Jack
~~~~ ~~~~
Left __[R1]___.__.__ Left
Right __[R2]___| |__ Right
Common _______________ Common

R1 = R2 = 1000 ohms

Thanks for any advice!

What do you mean by "two-channel mono"?
It may be me but I don't know what you want to do.

Tom

..

3. ### JKGuest

I want to plug one end of the patch-cord into an MP3 player and then
plug earphones into the other end of the patch-cord. Then, at *each*
ear-piece I'd like to have an L+R mono signal.

..

4. ### George H.Guest

The cheap 'ear bug' sitting on my desk has a resistance of ~ 30 ohms. So
with 1 k's I think you'll need some gain after the mixing. If you wanted to
do it without any post amplification then I think you could pick some
'mixing' R's that match the resistance of the head phones you are using.
You throw away 1/2 the signal that way, but it's simple.

George H.

5. ### JKGuest

Yes - L+R at each output channel.
OK. The mono device is just headphones.

My main concern was loading and/or cross-connection of the MP3 player's
output drivers - that's why I picked 1K mixing R.

Thanks for the reply!

..

Why?

Thanks,
Rich

7. ### Guest

Yes. That's how it's done.

8. ### JKGuest

At work, it's better to keep 'one ear open' and since my MP3 player(s)
don't have a stereo/mono select, this seemed like a good work-around.

..

9. ### Rich GriseGuest

Ah, got it.
Rich

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