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AV and Multimedia Related Thread, Hall AV equipment. in Technical; Finally, after a year of suggesting and this mornings assembly being a complete mess up, I've been given the go-ahead ...
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    maniac's Avatar
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    Hall AV equipment.

    Finally, after a year of suggesting and this mornings assembly being a complete mess up, I've been given the go-ahead to order some kit to permanetly install in the Hall for assemblies.

    At the moment we use a portable PA kit, laptop and lots of cables to make it all work. This has a lot of problems because bits get borrowed off the PA, cables go missing, kids play with the mixing desk when it's in storage behind the stage so it sometimes goes completely wrong when we've no idea what switch, button or cables been moved or unpluged - like this morning! The speakers are parmanently wired into the hall with 2 speakon connectors on the wall at the front where we hook it up.

    What I've suggested is we buy a seperate power amp, DVD player, rack mounted PC with pull out keyboard and monitor, and small mixing desk to permanely wire in in a 19" wall mounted rack at the front of the hall (as that's where the speakers terminate) that way we know the kit will never be messed with as we will hold the keys for its use! Drama can still use their existing PA when required, as we will leave the speakon connectors in place and hopefully, if I can find the right sort of switch box, have it so you can change between the two.

    So I'm looking for a professional speaker swich box which can be used to select between the permanetly wired in kit and the portable PA kit. It's pretty powerful stuff, so a normal domestic switch box is a no go. Anyone got any suggestions?

    Mike.
    Last edited by maniac; 8th February 2010 at 01:40 PM.

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    plexer's Avatar
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    Is there a projector in this mix as well either allready in place or going to be installed?

    Do you have a control box solution for that as well so that they don't need the remote?

    Ben

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    maniac's Avatar
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    Quote Originally Posted by plexer View Post
    Is there a projector in this mix as well either allready in place or going to be installed?

    Do you have a control box solution for that as well so that they don't need the remote?

    Ben
    Projector's already in place, that will be wired into the PC in the new rack, but also via a KVM switch they'll be a wall box next to outside the rack so the Dance teacher can still use her laptop, we'll make sure the KVM is switched over to the external connection when we leave the hall. We may possibly allow the dance teacher to use this kit once it's installed, but at the moment it's aimed at allowing assemblies to take place without all the drama that happens at the moment!

    We will still use the remotes for turning the projector on, we have about 6 of them with various people around the school, so that's not really a problem. I just need to ensure the people that use the screen, projector and sound equipment can still use what they have, and my new installation can be totally seperate and only used for presentation evenings, assemblies etc.

    I would like to dismantle what we have already and fix the whole lot in, but our Director of learning for Performing arts wants that PA to remain portable unfortunitely.

    Mike.

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    Andrew_C's Avatar
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    You could use any reasonable size switch, mounted on a plastic (or metal) patress plate. Unless the rig is huge, and run flat-out, then a 20A switch would be more than ample. Double throw-double pole is what you are after. The hot wire is switched, the cold can be commoned.

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    maniac (8th February 2010)

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    mjs_mjs's Avatar
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    You normally wouldn't switch the output of an amp, usually you switch the signal before it hits the power amp. Using a switch in this way could damage the amp's.

    Behringer do a nice and cheap line mixer which may be worth looking at.

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    maniac (8th February 2010)

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    maniac's Avatar
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    Quote Originally Posted by mjs_mjs View Post
    You normally wouldn't switch the output of an amp, usually you switch the signal before it hits the power amp. Using a switch in this way could damage the amp's.

    Behringer do a nice and cheap line mixer which may be worth looking at.
    The thing is, I don't wany any of the equipment in the new rack to be left on or for it to be left open at all, but Performing arts need to be able to use their existing PA still with the same speakers that are already fitted, so each set needs it's own amp really.

    It is really that bad to switch the output from power amps in this way, if so I might need to re-think my strategy?

    The problem we have at the moment is too many people are using the PA equipment and not putting it away properly, stealing cables and leads or messing with the settings on the mixing desk that it's taking us an age in the mornings to set up a simple assembly and quite often it doesn't work properly or sound very good as a result because sometimes we've no idea what wire they've moved or what setting they've changed. As most of the people using it have no real idea how it works, they tend to just move every single dial when it doesn't work meaning the carefully worked out settings that I spent hours testing get all messed up.

    The idea is seperate equipment which is permanely wired in and under lock and key to use for these events, and everyone else can carry on using what they do already. This way I know the hall will always be ready for an assembly or other event and I know bits aren't going to be stolen, borrowed or changed without me knowing.

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    RinSewand's Avatar
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    How about getting some speakon sockets(a) and putting them on the side of the cabinet, with tails into the cabinet, put another set of sockets(b) facing into the cabinet with tails that go to your wall sockets, cable from your amp to speakon socket(b) for your use, when you leave, plug in the tails from (a) in instead... external people come in, plug in to the side of the cabinet through sockets(a), no switching needed (just make sure the ones on the wall already are glued in or boxed over or something to people don't get confused?)

    Cheap solution

    RwD

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    maniac (8th February 2010)

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    nicholab's Avatar
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    Get a some nexo ps-15 speakers and a camco amps.

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    maniac's Avatar
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    Quote Originally Posted by RinSewand View Post
    How about getting some speakon sockets(a) and putting them on the side of the cabinet, with tails into the cabinet, put another set of sockets(b) facing into the cabinet with tails that go to your wall sockets, cable from your amp to speakon socket(b) for your use, when you leave, plug in the tails from (a) in instead... external people come in, plug in to the side of the cabinet through sockets(a), no switching needed (just make sure the ones on the wall already are glued in or boxed over or something to people don't get confused?)

    Cheap solution

    RwD
    That's a good idea, a little bit more complex than I had in mind, but would do the job. I was after a switch of some sort, but I've just been reading about power amps and switching speakers - it really isn't a good idea it transpires. Speakon connectors might be the best bet as they're easy and cheap to get hold of and wireup.

    Mike.

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    Andrew_C's Avatar
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    Quote Originally Posted by mjs_mjs View Post
    You normally wouldn't switch the output of an amp, usually you switch the signal before it hits the power amp. Using a switch in this way could damage the amp's. .
    Oh rubbish. You MIGHT conceivably if the amp was running flat outand you switched to open circuit, but really!

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    RinSewand's Avatar
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    Quote Originally Posted by maniac View Post
    Speakon connectors might be the best bet as they're easy and cheap to get hold of and wireup.
    Yup - plus if they get smashed it's easy enough to buy another connector and solder it on. Patch panels gave me the idea...

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    Quote Originally Posted by Andrew_C View Post
    Oh rubbish. You MIGHT conceivably if the amp was running flat outand you switched to open circuit, but really!
    Actually there is some truth in his statement, but it seems to depend on the power amp.

    Saying that, we would be in control of the switch, and would obviously make sure it is switched to the correct speakers before we turn it on, so might still opt for a switch of some sort. Just weighing up my options at the moment.

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    Quote Originally Posted by maniac View Post
    Actually there is some truth in his statement, but it seems to depend on the power amp.
    I'd be fascinated to know how! Please tell...

    One problem with Speakons is that it ISN'T intuitive how to unplug them, especially the ring-locked type. I've had to replace several that have been ripped out by kids. They are however, by far the best, and only dedicated speaker connector. Excluding the execrable DIN.
    Last edited by Andrew_C; 8th February 2010 at 06:06 PM.

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    I would have thought that kids should not be touching the PA in normal operation. Although by year 11 I was using a 40 channel desk and thousands of pounds worth of mics.

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    maniac's Avatar
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    Quote Originally Posted by Andrew_C View Post
    I'd be fascinated to know how! Please tell...
    I can't find the site I was reading earlier, but essentially it's not the amps it can damage, but the speakers. Some cheaper amps don't sense whether there's speakers connected or not, and can apparently accumulate high charges inside capacitors inside them which can blow the speakers if they are suddenly connected while the amp is switched on. A lot of better amps will detect if the speakers are connected or not, and if they are plugged in while the amp is on have a sort of 'sort start' system so the speaker won't blow.

    Saying that, according to what I was reading the risks are low and any decent brand of amp this will not be a problem, although speaker switch boxes aren't recommended on high output rigs by anyone, hence the reason I can't find any dedicated decent speaker switches. The speakers in our hall are 4 x 400w RMS output which is pretty powerful so I am warey about switching it.

    I might have a totally different appraoch for this now, as it's now possible they may go for having all the PA kit permanetly installed so I may not have to buy new stuff, just put the equipment we have in a decent rack and wire it all up properly!

    Please note I'm by no means an expert on PA equipment, Home audio yes, but this is different. I am probably the person who understands the most amongst the people emplyed at the school however, so naturally it's fallen to me to sort out which I don't really mind as it will make my life a lot easier.

    Mike.

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