Bad Audio Diary BAD 9: What's wrong with this picture?
Firstly, credit for the image. Er... I don't know who created it. If they would like to step forward and identify themselves I'll be happy to update this article.
Now the content of the image. Clearly this is wrong. Stacking up so many splitters into the headphone output is bound to lead to problems. As audio people we need to consider the details. Here goes...
What are we seeing?
We see at the bottom of this totem pole (traditionally the most respected position as it supports all of the others higher up) a stereo-jack-to-two-phonos adapter, plugged into the mixer's headphone output.
Into this is plugged a phono-to-two-phonos adapter, and a phono cable taking signal to who knows where?
Into this are plugged two phono-to-two-phonos adapters. The image is partially hidden but it looks like two phono cables bleed signal off.
After that there's more of the same, culminating in four phono cables sprouting from the last pair of adapters.
Whether all of this is mono or stereo, who can tell?
It looks wrong
This is sufficient reason not to do this. If you're a professional then not only do you have to act professionally and do a great job, you have to look professional. Why? Because your customers only have a partial understanding of what you do, maybe 10%. But they think they know more than they do. If something looks wrong to them, they'll probably pay you for your work but not employ you again.
This should be visible to anyone. The weight of cables and adapters is putting stress on the headphone socket. Yes it may work for a while, but the risk of failure is increased. And abusing a socket like this may make subsequent correctly-made connections unreliable.
It's electrically unreliable
If there were a schematic of this setup available, and the circuit was replicated in a die-cast box, professionally wired, then it would almost certainly work just fine (but there's more to say on impedance in a moment). But the strain and stress on the contacting surfaces here risk unreliable electrical connections. It may work; it may not work; it may cut out intermittently. For professional work, total reliability is the requirement.
Single point of failure
This is what we would call a daisy-chain connection. One adapter feeds through to the next and so on. Much more reliable is the star connection where all outputs connect directly to the input, which is how the die-cast box mentioned previously should be wired. In the daisy chain, if one component fails, all downstream signal flows are blocked.
Well we are looking at the headphone output of the mixer here, but we can't see where the cables go.
If they are going to line-level inputs, then the headphone output will almost certainly have enough current available to drive them all.
But if this setup is meant to drive several pairs of headphones, then if they are high-impedance headphones it's probably OK. If they are low-impedance then there may be distortion. If the headphones have a variety of impedances, some will be louder than others. Do you know the impedance of your headphones?
So why do it?
As you can see, there are plenty of reasons why you shouldn't do this. But sometimes, even at the highest levels of professional work, the unexpected crops up. There's a problem and it has to be solved right now. Perhaps this, at its own level of professionalism, perhaps a school or church and still rightfully respected, was the only solution available at the time. Of course, once the job is done, lessons should be learned and a better solution found for the future.
Still, it's a fun thing to see and I hope the job went well. I'm guessing that it probably did, but please have that die-cast box made up for the future, or buy a multiple-output headphone amp.