Splitter Buffer, 2 inputs to 1 output?

[Mandobird]

Trying to make a splitter with 2 inputs to 1 output, basically the reverse of the AMZ buffer splitter here:

http://www.muzique.com/lab/splitter.htm

It's for plugging a guitar into 1 input and a MP3 player into the other input, amp plugged into the output so you can practice to music whilst playing (no switching required, as both inputs will always be fed to the output).  Anyone know if it can be done?  Is it enough to rearrange the AMZ schematic for 2 in/1 out (somehow)?

I found lots of stuff for 1 input to 2 outputs, but haven't come across anything for what I'm after.  I imagine just passively splitting both signals to the amp would result in signal loss and wouldn't sound very good.

Thanks.

[mth5044]

http://www.runoffgroove.com/splitter-blend.html

But I think you can buffer the guitar in and then mix it with two resistors to the line level in to the output.

[jimilee]

Also, guitarpcb.com has the paramix pedal.

[garcho]

Search for summing amp, or diy mixer projects. Super simple with an op amp or two.

[GibsonGM]

Maybe this, "summing amplifier", with a pot for Rf.  Really simple:    http://www.ecircuitcenter.com/Circuits/opsum/opsum.htm

I've used this basic design for a lot of that kind of work, and it does fine with most any opamp.  
You can use all 3 inputs, or just omit one...   

10K input resistors (you can use a pot to make their levels approx. equal) and maybe try a 50K or 100k pot (?) YMMV, watch your output level if you use a big pot!
Use a dual power supply (+/- 4.5v would be fine), and don't forget blocking caps at input and output!  1uF or whatever, to taste. 

[knutolai]

Remember that the signal from your MP3 is a stereo signal. two signals. So you would need 3 inputs, though two of them would be connected to the same socket.

[PRR]

> basically the reverse of the AMZ buffer splitter

The opposite of a splitter is a mixer.

Electrically quite a different thing (when covering all bases).