Mass Headphonage?

[Bowlee]

So...I'm in college and since we couldn't have real drums in the dorm my roomate just built some with some mesh heads and Pearl Traveller kit. It rocks my socks off, but it does not rock my RA or the guy below us because the kick drum is kinda loud.

So anyways we knew that we would have to get head phones for it....but what do you people think is the best way to go about setting it up so everyone can hear each other through the headphones?

I was thinking...that I could just run everything through a PA and then use that out...and get some kind of device where it splits the signal multiple ways....would that mean I should get a mixer?? Or some kind of crazy device that they use for like language classes where everyone can hear one thing?

What do you people suggest?

[Slipstream]

That's an interesting problem. It's something that many of us would like to do (myself included). My mixer has only two channels out. I know high-end mixers have an out for each channel. I wonder what a guy could get that would do the trick for the average guy's budget. Those high-end mixers are pricey! Maybe one of those 7.1 soundcards?

[b3n]

Here's an idea - have you seen those little headphone 'splitter' things? You plug one end into the mixer (or discman, ipod etc) and then plug two sets of headphones in. I see no reason why you couldn't just plug 2 more into the first one to get 4 headphone sockets. It's a bit of a bodgy solution I know but on a budget what else can you do but bodge?

Anyway, I'm sure someone else will have a better idea than that so feel free to ignore it.

[crusty]

Problem with splitting the signal more than twice is the loudest sound you can get will also drop with each set of phones you add. Also, if all of the phones aren't the exact same brand and make, there's a good chance they won't all perform the same way and some will get lots of volume, and other will get too little. There are multiple headphone amps you can by, but I don't know how much they cost. In those each person has thier own headphone amplifer with it's own volume control. Without something like that what you could do is split the signal n-ways, but the each person then amplifies thier share of the output somehow, like with a stereo line-in or something (so you'd need some sort of amp with a phones out for each person).

[Slipstream]

I think ya hafta worry about matching the impedence.

[crusty]

I think ya hafta worry about matching the impedence.

I'm not an expert, but I know you can get phones with impedance values anywhaere from less than 100 ohms to over 600 ohms. With that kind of varriance, the output stage of the amp has to be able to handle a low impedance - say two pairs of 100 ohm phones in parallel to a total of 50 ohms - should be able to handle it. I guess reducing that down to 25 or less could cause problems unforseen to the manufacturer. If you split the signal four ways (or more) and feed it into four or more amplifiers, the input impedance of an audio amplifer is usually at least 10000 ohms, four in parallel would be arround 2500 ohms of load on the output of the main headphone amp - high loads shouldn't be a problem.

[Slipstream]

I'm not an expert, but I know you can get phones with impedance values anywhaere from less than 100 ohms to over 600 ohms. With that kind of varriance, the output stage of the amp has to be able to handle a low impedance - say two pairs of 100 ohm phones in parallel to a total of 50 ohms - should be able to handle it. I guess reducing that down to 25 or less could cause problems unforseen to the manufacturer. If you split the signal four ways (or more) and feed it into four or more amplifiers, the input impedance of an audio amplifer is usually at least 10000 ohms, four in parallel would be arround 2500 ohms of load on the output of the main headphone amp - high loads shouldn't be a problem.
Makes sense. I've been thinking about if you have four sets of headphones, and have two sets in parallel - connected in series with two other sets that are in parallel, then you should be back to the original impedence. Did I explain that right?

Anyway, another thing that bounces around in my head. I know it's important to have a load on your amps speaker circuit, but when you plug in headphones, and the speakers are cut out, where does that power go, if not to the speakers? It's not the same amount of power that goes to the headphones, is it? And the impedence of the headphones isn't anywhere near what the speakers are (100 ohms +- vrs. 16, 8, or 4).

And input impedence, such as guitar v. mic, balanced/unbalanced, etc.

I'm so confused. Can you recommend some reading? :confuse:

[crusty]

I think having a load on the power amp (ie. speaker or hot plate) is only neccessary it there is actual sound going through the amp. If the speaker isn't moving in an out there's no current therefore no voltage, no power, so nothing to worry about. If you cut off the signal before it goes into the power amp (which is what happens when you plug in the headphones) Then you can disconnect the speakers without any problem (which also happens when you plug in the headphones.) As for the signal that gets sent through the phones - it's much lower power, say 1/4 watt.

Guitar and mic output impedance should be about the same. Unballanced is what you get from a guitar. It's just a hot signal and a ground. A ballanced signal is generally used for mics and has two hot wires and a ground. The two hot wires carry the same signal but it's 180 degrees out of phase (the crest of one wave occurs at the same time as the trough of the other). What happens when the cables are long enough is radio interferance is picked up on the cable is canceled when the two hot signals are mixed. Mixers that accept ballanced mic cables have a matching transformer on the input of each channel to mix the two out-of-phase signals.

I'm afraid I don't know of any sites for this stuff, I learned it all at college.

[Slipstream]

Well that clears up a couple things, thanks.