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Squealing coming from System in school through Simplex PA - TV Studio with Ultra Curve

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Michael Spano
Squealing coming from System in school through Simplex PA - TV Studio with Ultra Curve
on Jun 15, 2016 at 11:59:48 pm

Hello All,

I'm hoping someone can help me out.

I have been having some issues with squealing coming through my PA system at the school I work at.
Let me explain my setup first...

Right now I have two HDMI cameras and a computer (iMac) via display adapter to HDMI connected to a Black Magic Design TV Studio. For sound I decided to not use the built in HDMI sound from the cameras so I can have more control and options. So to get sound through the system I have an Allen&Heath ZED 14 with a table mic, hand mic, and hanging mic connected to it. I also have a computer connected to the Allen&Heath via USB (the same computer I have video outputting to the TV Studio) so I can play music as well as pre recorded video etc.

From the ZED 14 the two outputs go to a Belringer Ultra Curve that is then output via SDI to the TV Studio in case we want to record with sound. From the TV Studio, the digital output goes to a SDI to Analog converter (Black Magic Design).

This is where it gets dicy...

Originally I had the analogue converter video output going to the RF modulator so I can send the video signal to the TVs around the building (this is primarily a morning announcements type deal) and the audio (left and right) going to a Whirlwind PcDI to cut out any digital noise or squealing out of the signal before being split. The one side of the split goes to the Simplex PA system for audio around the building and the other side goes to the RF modulator for sound on the TVs.

We were having issues with sound not coming through the PA so the guys at Simplex came in and determined that the sound gets significantly softer when run through the Whirlwind so the system isn't able to pick up a signal and either doesn't turn on or it cuts out randomly.

Today we decided to try and cut out the Whirlwind box and, while the signal comes through loud and clear and comes through the speakers, it also comes with a horrible whine or squeal.

My question... Is there a better way to set this up to get rid of the squeal and not degrade the power of the signal going to the PA?

I was messing around and currently have the ZED 14 connected from one of the outputs directly to the Whirlwind and from that going out to the PA. No Squeal, nice and loud. If I go directly from the ZED to the PA I get the squeal even with nothing connected to the board (thinking it was the computer or some input causing the issue)

Maybe someone out there is using a similar setup for a school morning announcements program that can shed some light here. I'm not a dummy when it comes to this stuff but I am completely dumbfounded trying to figure out how I can output from the board to both the PA and the RF while also allowing the sound to go through the TV Studio so we can record during class for other projects.


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