Hello everyone!

Long-time viewer, first-time poster here. I work for a pretty large school district that has been around for quite some time. The systems in place here are well out of date and with that comes lots of technical issues. As A/V Admin, it's my job to understand and resolve them when it comes to anything sound or video, and recently I ran into an issue I've never seen before.

The previous installation of this room was done sometime in the 70's. There is an old power relay connection to a newer RDL ST-ARC1 audio relay for the announcement system. There is also an amp in the room that should be outputting signal to the power relay whenever the announcements are silent, but therein lies my issue. I have tested the amp and it works fine. The line stops at the power relay. So my supervisor and I decided it was time to replace it.

I'm pretty unfamiliar with relays as I have never had to work with them before. I took the time out to do some research and I think I have come up with a decent design that isn't too expensive. Just to list the needs: signal comes from an (1) amp in the office and an (2) amp in the room. The room amp needs to be silenced when the office amp comes through so the voice can be heard. Once the announcements are over, the room amp can be heard again. I have attached a schematic (very rough) for what I believe would work. Can anyone confirm that this is correct? If not, suggestions for how to better design this would be greatly appreciated!

 

I have attached a schematic (very rough) for what I believe would work.

You mentioned it is very rough so a few questions.
What are amplifiers 1 and 2 exactly? I ask because the ST-SSR1 is designed for line level audio switching.
What is the output of the SSR1 connected to exactly?
Your drawing seems to show it connected to speakers.

 

You mentioned it is very rough so a few questions.
What are amplifiers 1 and 2 exactly? I ask because the ST-SSR1 is designed for line level audio switching.
What is the output of the SSR1 connected to exactly?
Your drawing seems to show it connected to speakers.

So the amplifier (which I am not exactly sure if it is an amp or not) that is connected to the "Select Input" is a line level input coming from the offices announcement system, this I have confirmed. The amplifier that is connected to the "Normal Input" is the output from the amplifier held in the room.
I have the output of the SSR1 connected to a barrier terminal to output to four ceiling mounted speakers. I see now that the inputs should most likely output to the amp in the room to then send to the four speakers?

 

WE have NO information about the audio switcher, which I would not call it a relay. In addition, we have no information about the signals from the amplifiers, such as impedance and voltage. For that "ST-SSR1" device we do not know the rated power capacity nor the controls voltages, both of those matter. I have installed sound systems and not come across such a device because of never needing it. Most systems do not operate that way.
A normal PA amplifier has multiple signal inputs, and often an input to allow one source to take precedence. (to take over)
PA system remote speaker connections are often specified by voltage, such as 25 volts, 70 volts, or 140 volts. (those are the voltage at the amplifier's rated output power.)

 

So the amplifier (which I am not exactly sure if it is an amp or not) that is connected to the "Select Input" is a line level input coming from the offices announcement system, this I have confirmed. The amplifier that is connected to the "Normal Input" is the output from the amplifier held in the room.

Can you post model numbers of both amps please.

 

Much more useful than model numbers is actual information, although model may allow knowing about ifit has a pecidence takeover option.
But with the information from post #5 it is clear that the "line level" signal will not drive speakers. Thus it is a case of having the outside line level signal take precedence over the local inputs. THAT is a common function in some PA amplifiers. It does not require an external changeover relay. It may require a DC control signal, however.
How many classroom systems are in the system???

 

Sorry for the silence, I actually got it figured out. I used the ST-ACR1 in conjunction with the SSR1 to trigger the select input. The system is running now, thanks.

 

I am now wondering as to what type of PA amplifier you have, and does it have a precedence function to select one input over the others when it is asserted. So brand and model would be interesting.
And I still wonder how many rooms there are with PA systems.

 

It's an Biamp MXA75 and it does have priority switching/auto muting per channel. There are over 100 classrooms in this wing of the school, but only three of these larger rooms are on the same output from the office. The trouble from this whole situation arose because the teacher wanted a specific way to hookup his computer and play music, so it essentially became a relay going to a relay. Again, it's been figured out now and I have the wiring diagram attached that I used if anyone is interested in that as well.

 

It's an Biamp MXA75 and it does have priority switching/auto muting per channel. There are over 100 classrooms in this wing of the school, but only three of these larger rooms are on the same output from the office. The trouble from this whole situation arose because the teacher wanted a specific way to hookup his computer and play music, so it essentially became a relay going to a relay. Again, it's been figured out now and I have the wiring diagram attached that I used if anyone is interested in that as well.

Oh Wow!! That is the most useful wiring diagram I have seen in a long time. Very good!
It is possible that it could have been achieved with only that relay module, using the precedence function on the existing amplifier. Slightly less complex, but the same function. It might have removed the XLR external connection.

 

Thanks!! And ah yeah I agree, I see now how I could have. The only thing is that the external XLR connection has the option to send audio into the system as well, which I have the precedence function set as a back up in case the relay fails. Hopefully all works well though! Thanks for the help!!