So I've got a bass and an electric guitar, and I'd like to have their combined sound in two pairs of headphones.

It'd be great if I could put them through their amps and combine the sound out of the headphone out, so I can use the distortion on the guitar amp.

The guitar amp has headphone and speaker out, but the bass amp only has headphone out. I also have a powered 4 input mixer that takes 1/4.

I can't find a combination that works. I really don't know what I'm doing. Even plugging a Y splitter into the headphone jack of one of the amps gives me dead silence through both pairs of headphones

Could someone fill me in on what I need to do here?