I've got a guitar and a bass with separate amps. I want to be able to get sound from both amps into two pairs of headphones.
But I can't even get the sound from one amp into two headphones. When I plug a Y splitter directly into the headphone out of either amp, neither pair of headphones produces any noise.
What is going on?
First of all, it sounds like your Y-splitter is either defective, or something is basically wrong with it. It's also possible that the headphone jack doesn't provide enough juice to drive both headphones, or one of your headphones has a short or something.
Now, to your real issue. What you need is a small, basic mixer, that you can plug each separate amplifier into. You'll use your "line out" or headphone out to go to the mixer, NOT the speaker out. Then, you plug your headphones into the mixer, adjusting volumes/balances to your preference.
More likely than not the Y-cable is not for splitting a 6.3mm stereo signal to two 6.3mm stereo outputs.
At any rate, it sounds like you want to hear one amp left, another right. When using the normal connectors of your headphone, you'll be making a ground connection with your amplifiers and more likely than not they have independent grounds already. That gives you a ground loop which is cause for hum.
Now if your headphones are isolated from your head, it's possible that they don't have a common ground except for the connector. If that's the case, it might be an option to cut off the connector and solder two independent mono connectors to the two separate shielded cables at the amp end. This only makes sense when the cables are of the kind only joined by plastic and could be pulled apart without having any wires show.
With two isolated and separate earphones, you should be able to connect to two different amps without problems. However, the amp output will tend to be for a stereo connector (TRS, tip ring shield) with tip and ring both connected to the output. If you insert a mono plug, it will shorten ring and shield, consequently shorting the whole output.
More likely than not that's what you currently are doing with your Y cable.
So whatever you do, you'll need a full stereo TRS plug in the headphone socket of your amp that does not connect R and S.
To do the job properly, you need a headphone amp., which will have the facility to mix each signal, and also attenuate the sound. Useful if one amp is louder than the other, or the headphones are of different sensitivity. I use a Behringer - small, lots of options, and inexpensive. It will sort out the mis-match you have with the sockets on the amps and the headphones you're using.
Something like this may be useful http://jamhub.com/bedroom/. You can connect multiple instruments and create multiple independent headphone mixes.
DISCLAIMER: I have never used it myself and it's not intended as a sales pitch.
