Sound on the Fly

[mstaylor]

I have recently been given the resposibility of handling the projectors and mic setups for meetings in my multiuse building. I am the SM/Head Rigger for the main preformance area and because of ecposure to the technology I have been morphed into a tech.
Yesterday I went in to set up two projectors for Powerpoint presentations, simple right? It was until they decided to turn tthe room and everything had to be redone. Then they added lapel mics. This is where the problem arose. We have seven meeting rooms that can be seperated by air walls. The speakers are 70v ceiling units. I can turn either room on or off and put the inroom mic inputs into it. What I can't do is have one mic inputing in room seven and another system in one. We have podiums that contain it's own sound system, complete with a condenser mic. I tried to take the lapel base and input it into a dynamic mic input on the podium. All I could get was a loud hum. The XLR to 1/4 adaptor was unbalanced so I figured I needed a TRS 1/4. Off to the electronic store, no change. The I realized the Shure base has a 1/4 jack in addition to the XLR. I tried both balanced and unbalanced, same result. I'm at a loss at this point.
As a side note, the 1/4 jack on the wireless base is unbalanced, why?
As I have noted in past posts, I am a light guy/rigger. I have enough soound knowledge to be dangerous.

[avkid]

What model is the wireless?

[mstaylor]

Shure PGX lavolier but I tried it with a Shure 58 wired mic. The wireless was fresh out of the box, had to set it up on the fly also.

[museav]

Sounds like you are using a wireless mic and the "base" is the receiver. I'm not clear on what you are connecting it to as you referenced the lectern having a condenser mic and then noted connecting the wireless mic to a dynamic mic input.

Tht PGX receiver has both a 1/4" line level output and an XLR nominal mic level output, so instead of using the 1/4" output on the receiver you want to run the XLR output on the receiver to the XLR mic input.

[mstaylor]

The lecturn has it's own little system, amp, speaker and inputs. The mic that comes with it goes to a condenser input. There is a second input marked as dynamic. I tried both hooking the wirelss base and a regular corded 58 to it. The input in the podium is a 1/4 in input so I had to convert from XLR to 1/4. I tried both balanced and unbalanced 1/4s.

[howlingwolf487]

mstaylor,

Can you supply us with a Make and Model of the podium (I'm assuming it's actually a lectern, but don't feel like dealing with semantics just yet).

[mstaylor]

Oklahoma Sound https://www.schooloutfitters.com/cat...cts_id/PRO1324
And you are correct it is a lecturn.
It doesn't show the controls but it does have a built in wireless but we don't have one. We only own the corded mic.

[howlingwolf487]

Oklahoma Sound https://www.schooloutfitters.com/cat...cts_id/PRO1324
And you are correct it is a lecturn.
It doesn't show the controls but it does have a built in wireless but we don't have one. We only own the corded mic.

That is an interesting lectern...the microphone inputs look as if they are made for High Impedance types. There are no specs on the amplifier/mixer section, so I can't really tell you any more than that unless you could contact the manufacturer.

[FMEng]

The lectern manufacturer doesn't provide any useful specs for the inputs, even in the user manual. But I do know that the Shure PGX4 receiver has a pseudo (impedance) balanced output. What that means is that only pin 2 of the XLR has audio on it. Pin 3 is just a resistor to ground. If your cable is wired with pin 2 to the wrong phone plug conductor, it won't work.

Take your soldering iron to the XLR to TRS cable, and swap the wires on pin 2 and pin 3 inside the XLR, and I bet it'll work.

[museav]

It's not unusual for sound lecterns to have a 1/4" mic input that is for high impedance, unbalanced mics, although using a 1/4" jack for the primary 'condenser' mic input is rather unusual.

Interesting that the Shure PGX output is a true balanced output (it is the impedance balancing that makes it a balanced output) but does not use signal symmetry with audio only on Pin 2.

SESCOM, Hosa, Horizon and others make both inline balanced XLR to unbalanced 1/4" TS cables and inline matching transformers, either the cables or inline transformers are in the $10 to $20 range. Most of those use Pin 2 for the 'hot' and thus should work.

[mstaylor]

I appreciate you guys trying to help. I actually have three of these, two are lecturns and one is a podium. I tried all tricks in my very limited bag of tricks and I was lost. As I keep telling my bosses, light guy.