Adding "aux" input to Little Gem Mk2

[JSC]

Hello all-

New here; I'm just starting to get into amps after rewiring and refurbishing a couple of guitars and a bass.

For my first amp project I built a Little Gem MK2 from Runoffgroove.com as a tiny practice amp. It works well and sounds fine (depending on the speaker- I added a switching 1/4" jack to it so that I can plug an external speaker into it when it's not being portable.)

Anyway, I wanted to add an auxiliary input to the circuit so that I can run the headphone output of an mp3 player through the same amp for practice. Searching the forums here and googling has not turned up the info I need on how to do this w/o damaging the circuit. Link to the circuit's page:

Little Gems

Since it's just for "playing along" practice it doesn't need to sound particularly great, just so I can hear it and keep time w/ it.

Any pointers on where I can look for info on how to match the headphone output to the amp's input? My previous electronics experience is mostly w/ microcontrollers, so audio is still largely a mystery to me.
Many thanks for any tips or pointers to info.

JSC

[Jazz P Bass]

Most 'headphone out' circuits can be used as is for a preamp signal.

[JSC]

Most 'headphone out' circuits can be used as is for a preamp signal.

Do you think it needs anything to isolate it from the rest of the circuit? The original guitar input goes through a JFET and cap before going into the input of the two LM386 amps.

I figured that I don't need anything to adjust the level of the mp3 input since I can just use the player's volume control.

JSC