100V Line Speaker Systems

[stillwave]

Hi all,

 

We currently have a 100V line system installed in our venue for show relay & paging to dressing rooms, at the moment the show relay is via a microphone placed on or near the SM desk next to a monitor from the house PA (not ideal as can hear the SM & stage background noise in the show relay)

 

I suggested a direct feed from the house PA as this would eliminate any background noise (feet shuffling, people muttering in the wings). the sound guy isn't happy with this as there wouldn't be any isolation between his system (house PA) & the 100V system.

 

It would be possible to get a pre amp or a post amp signal from the house sound, if this helps?

the input to the 100V line system is via a 1/4" jack at line level

 

My questions are: is it possible to connect an input of the 100V line system to the house sound but isolate the house PA from the 100V line system? can it be done cheaply? is it as simple as a DI box?

 

Thanks for reading.

 

Regards,

 

Ben Wainwright

[timtheenchanteruk]

a passive DI would work, or an isolating transformer.

 

if its not a fixed in house PA, then ideally a connection point somwhere near where the PA operates from, a couple of places I work expect this feed directly into the amp, which is at the side of the stage, and another cable to run, Id be much happier if I could just plug straight in.

[paulears]

I cannot see why he isn't happy. Does he connect his desk to foldback amps for monitors, or perhaps gives a feed to somebody with a video camera. The things are designed for the purpose of providing outputs for other people or other people's kit. If he's really worried then hanging a DI onto one of your mic inputs and gettng him to 'allow' one of his line outputs from duplicate main outs or a spare aux will work and give him the isolation he desires.

 

Personally, show relays seem best with a mic above the stage. Not much amplified sound from a play or something even like an acoustic only big band. The idea of a show relay is to let people hear what's on stage. I'd happily suppliment this with amplified sound - for the best of both worlds, but an output from the desk relies on having the right inputs - and that can be difficult to manage and monitor. Maybe it's this extra mix he's worried about? After all, it doesn't take much to knock a knob and have either nothing through the relay, or even worse - the wrong thing!

[Jivemaster]

An isolating transformer would ensure that there were no potential or earth loop problems, however on acoustic shows there may be no sound mix so then there would be no show relay! FAR better to use the present system and if possible reposition the pickup mic.

[KevinE]

It might be worth telling him that the 100V line system is probably less voltage than a typical 8-ohm PA rig which will output alot higher voltage at full tilt.

 

Other than that the line and mic level signals will be compatible.

[dbuckley]

Personally, show relays seem best with a mic above the stage.

I usually have PCC160s at the front of stage, and use those for the show relay feed, irrespective of what else I might have available.

 

Back right on topic, many 100V amps have transformers on their inputs, and so by just not connecting Pin 1 on the XLR you have an isolated feed.

[stillwave]

Hi all,

 

I'll elaborate some more, the sound equipment (house PA) is on a different electrical phase to the 100v line system. I might try the overhead mic trick at some point but still would prefer to try the house PA tie-in, there are 4 inputs into the 100V system amplifier/mixer. the out from the desk isn't much of a problem there are padded -10db for recording and many other mixes. The majority of the shows we put on use the house PA, those that use their own PA are usually professional enough to use a watch to know when they are due on stage.

 

the inputs into the 100v line system are Jacks not XLR, I guess he's bothered about a fault on the 100v system affecting the house PA, that & the different phases.

 

Thanks for suggestions so far.

 

Regards,

 

Ben Wainwright

[paulears]

If you plug your sound system into anything on the same or a different phase, then at worst it goes - Hummmm. So rather than give your visiting companies no relay at all, and no doubt the presence of speakers on the walls will make them ask - and be p*ssed off by your suggestion of using a watch! - why not just try it and see. If it hums, then a DI will sort it, or on a line level feed, just disconnecting the screen could cure it.

 

It seems to me that if moving a mic or investigating a DI is too much trouble for the sound man, then it's time to get a new one. Simply because the current system could be made better easily, and having no show relay at all cannot be better than what you have at the moment?

[rooftop]

Our system, which I installed five years ago is very similar - we use three inputs into the 100v line amp

 

1) Paging mic in prompt corner with on/off switch and Ding-Dong

2) Over head stage mic

3) Balanced line feed from FOH P.A. This is derived from the Main Out of the desk. We've never bothered with an isolating transformer - afterall the 100v line are the outputs, not the inputs. If he's worried about the 100V blowing up the desk then it's no worse than the [probably] several kilo watts of power (driving the FOH PA) also plugged in to the desk!

 

For the touring shows that bring their own PAs, the over head mic will pick up enough for them to hear what's going on.