Switching multiple lines

[sideshowmark]

Hi clever peeps :D

 

I want to wire up some sort of switching box - I want to run 2 audio PC's in parallell - one as master the other as slave - rather than run two sets of lines into the desk I was wondering if I could make/buy a rack mounted switching unit - it would need to switch 2xMIDI I/O 8xXLR & 1x15wayDSUB from one source to the other all on one switch - I'm a bit of an electronics newbie so I apologise if this is a dumb question - if this IS a really dumb question if someone wants to suggest a good book/website to get me started and I'll find my own way.

 

I would imagine that I would have to step down a 240V supply then use it to run a load of relays triggered by one switch - is this the best way or is there something else out there? I would also imagine that anything I made like this could introduce a lot of hum ;) into the system - so some suggestions about preventing this would be coolio.

 

This is more of a theoretical question than an urgent need but I'm sure someone somewhere has done it before - I probably could just get Orbital to make me one but it can't be that hard - Can it?

 

Cheers

Mark

 

Ps Be kind!

[dbuckley]

The Show Control Changeover Switch might that for which you seek...

[sideshowmark]

D'ya reckon? ;)

 

Cheers Buckley - now if I can only hack into their system and get the wiring diagram... :D

 

this doesn't appear to switch audio as well... is there a simlar box for that too or do people just switch audio on the console?

[broadcast_techie]

Are you wanting to switch live audio?

[dbuckley]

Cytec general purpose matrix relay box

 

I've used these boxes for a few things over the years, and they pretty much rock.

 

Next!

[sideshowmark]

The Reason for running 2 pc's is so that if one crashes for whatever reason you can switch to the other - ideally the two pc's are synched so that playback 'is not affected - I've never actually had a show control PC crash - I like to think it's because I build my own and so there is enough power/memory/compatability to prevent it - so it's amost certain that it's dumb luck!

 

But if the master machine has crashed the playback is probably trashed anyway/late on a cue whatever - the audience know there's been a prob so not much point probably no hiding the crossover - crossfading seamlessly from one machine to the other is as pointless as it is difficult (surely?)

 

The setup I'm working on at the moment only uses 4 XLR outs from the PC's. but I'm experiementing with a small system so I can build a bigger one without wasting too much money... ideally I'd want to run 32 XLR outs from each PC giving me 16 stereo lines - taking up 64 desk channels in total unless the switching occurs pre-desk

 

I just though that as I need KVM, Gameport and audio switchover it would be easier on an engineer if they were all on the same button.

 

I use the MIDI to recall desk states so if the backup is needed the slave machine will need programing with different q nos to make the new channels live

 

or am I missing a trick?

 

 

Just saw your new post Buckley after posting this one - you obviously have all this prepared and ready to go! do you use the autograph one for PC and the matrix for audio or can the matrix do all of the above?

[dbuckley]

Just saw your new post Buckley after posting this one - you obviously have all this prepared and ready to go! do you use the autograph one for PC and the matrix for audio or can the matrix do all of the above?

Nope - I use one PC, dedicated to doing shows, and if it dies, then the show dies with it. Hasn't happened yet, though. Then again, I'm in the amateur space, so I dont do shows every day, neither to thousands of punters. If I were, then I'd take the issue of resiliant show control rather more seriously. In addition to the switching you want to do, I'd also need DMX512 switching, as for me it all comes from one machine.

 

The matrix boxes I've used in installs in City of London dealer systems (this is a good few years back) to switch many assorted signals for automated softpatching, so selected traders can have two desks, and have all their services available at either with the press of a button. Pretty cutting edge at the time, but with the much improved technology, now a standard feature of most trader suport systems.

[mackerr]

if you want to build your own, there are companies that make switches with pretty much as many contact as you want. T-Bar makes toggle switches up to 144 pole double throw.

 

Mac

[henny]

ideally I'd want to run 32 XLR outs from each PC giving me 16 stereo lines - taking up 64 desk channels in total unless the switching occurs pre-desk

 

 

quesion?

 

howmany channels will you be outputing from your desk to your pa, if you are just running 2 chanels (L and R) why not do the mixdown in the pc?

 

ian

[sideshowmark]

how many channels will you be outputing from your desk to your pa,

The last time I did this I had 14 different mixes - audience surround - onstage props - backstage calls - FOH calls - the works - but only one PC as didn't have time to sort out the switching for a backup. Thanks for the tip Mackr - those are the sort of switches I was looking for - I think I'll try and make one and see how much of a pop on the system when swapping over.

[Ben Langfeld]

To be honest, it doesn't really matter if it's just for redundancy. With this kind of system, playback would be interrupted anyway, so switching over transparently is pointless. You can mute the channels on the desk and switch it over without worrying about noise.

[dbuckley]

... backstage calls - FOH calls ...

Good to see I'm not the only nutter who does this sort of thing with show control :(

 

Thanks for the tip Mackr - those are the sort of switches I was looking for

My jaw hit the deck when I waw the number of poles available. That thought is stored away for the day I need it...

 

As a solution they will work fine for switching audio and other non-data lines. The only reason you get audio pops is difference in DC protential, and if turns out to be the case then just add a 4K7 bleeder resistor between each audio feed and ground, that'll normalise the DC potential to zero. Switching MIDI and DMX512 is harder, as you could be mid-packet at the point of the switch and thus get a data glitch, which may (or may not) be problematic.

[phil dekked]

I`m glad someone asked this question

 

On an install we maintain they have two music venues and want to be able to record from both. At the moment one room has a 32ch stage box split up to the recording desk with isolating transformers in-line. The other room ( down two floors!) runs a 24ch system from a wall mounted vdm down to the racks in the basement.

They want to be able to switch between the two rooms at the recording end!

 

 

option 1) is to split the downstairs and run a cable up to just before the balancing transformers upstairs and then terminate to a vdm plug. Cut the exsisting cable from the upstairs room and terminate that to a vdm and then put a wall mounted box female vdm. So you just " plug in" the room you want?

 

 

option 2) ( same cable setup as option 1) and use a patchbay with tie lines and normalising jacks..? both feeds come in and you " patch in" the room you want?

 

 

option 3) The toggle switches look like a good idea BUT how reliable over 32chs of recording audio?

 

option 4) anyone got a better idea!

 

thanks

 

phil

[dbuckley]

Why shouldn't it work...? It's just a bunch of switches...

 

The audio should be fine as it's all low impedence stuff, but there are two problems I forsee:

 

a) Crosstalk - likely to be low level, but the possibility for crosstalk is there, as the balancing of the signals is lost in the switch, and just outside it, and

 

b) phantom power - only one of the venuettes you mention has split trannies. If both have splitter trannies then the problem goes away. I suspect you want to switch before one set of trannies, but that is more troublesome on every front than switching after two sets of trannies, as then the sources is always known (it's s winding on a tranny!), theres no grounding issues, as the recording system is totally isolated from both rooms equipment, and no phantom issues as you dont need phantom to run the trannies.

 

c) Better idea - go all digital with two sets of A/D converters...?

[Soundie]

option 2) ( same cable setup as option 1) and use a patchbay with tie lines and normalising jacks..? both feeds come in and you " patch in" the room you want?

 

I would have thought that this would be the most sensible and flexible option, barring issues regarding phantom power, splitters etc.

 

It would be particularly useful to be flexible to be able to patch from one venue, through your basement recording room, to the other, send feeds back upstairs to different places etc.

 

Being able to access different channels from different installed cables at once gives you a lot of flexibility, and you never have too much of that.