This seems to get asked a lot. I’m bored so let’s explore it a bit.
A VISUAL EXPLANATION ON HEADPHONE CABLE ADAPTORS
HEADPHONES:
A transducer needs two things to work and make a complete circuit, right? Connection to a source and ground. Or a positive and negative ( + / - ). You need this for each transducer, so, you need 4 wires per headphone.
The negative ( - ) connection can be shared between the transducers with a common ground. That’s how a TRS (tip ring sleeve) 1/4" connector functions. Tip = L+, Ring = R+, Sleeve = shared ground ( - ).
This works fine. Connected to a single ended amplifier, the electricity flows through both transducers to ground, no problems.
AMPLIFIERS
There are many ways to build an amplifier for headphones, but we’ll keep it simple and talk about balanced dive and single ended types.
Balanced: Each connection is actively driven. For each transducer, one connection pushes while the other pulls.
Single ended: Only the + connection is driven.
CONNECTOR TYPES
4 pin XLR connections:
Using a 4 pin XLR connection provides a dedicated wire for each connection on a balanced amp. Great!
Single ended amps can also use a 4 pin XLR connection, mostly for convenience.
Either way, having 4 dedicated pins/wires is nice to have.
3 contact TRS (Tip Ring Sleeve) 1/4", 3.5mm, etc, connections:
Balanced amps can also offer TRS jacks for convenience, although half the amplification is unused.
Single ended amp driving a 3 connection TRS cable and headphones:
PROBLEMS
Where we run into issues is when we short active amplification to each other. If we convert a 4 connection XLR to a 3 connection TRS plug, we are REDUCING the number of pathways. By doing so, it then creates a short circuit across ALL of the active amplification sections. (You can draw a path from any single amplification section to any of the other amplification sections in the example below.)
Poof. Bad. Flames and smoke.
As you can see, all active amplification sections may now interact with each other via a single short circuit.
CONCLUSION
All of the above is just a really long winded way of saying: Going from the amp to the headphone, do not REDUCE the number of contacts / wires / pins.
Do not covert a 4 pin connector on the amp into a 3 pin connection for the headphone cable.
This, however, is just fine:
