Elk Output 1 (Voice) as input to intercom station

[project_x]

I'm looking to get the voice output of the elk to come thru on my intercom. I have a M&S DMC1 and have several extra stations, one of which that has a broken speaker. I want to "Monitor" this station and replace the microphone (the speaker) with the output of the elk.
This way the voice commands will come thru my intercom.....
Does anyone see any problems with doing it this way?

 

[Del91574]

Impedence matching would be a must. Not difficult but must be accounted for.

 

[apostolakisl]

There is a post in here on how to take the speaker level out from the Elk and convert it to a line level out. I think it is also on Elk's website.

 

[BraveSirRobbin]

I wound up not using the capacitor.

http://www.cocoontech.com/forums/index.php?showtopic=3950&hl=preamp

 

[project_x]

I wound up not using the capacitor.

http://www.cocoontech.com/forums/index.php?showtopic=3950&hl=preamp

I made the line level converter, and connected it into my intercom system. The Voice commands are at a perfect level for my intercom.
The only issue I have, is that there is a hum the entire time through the intercom system.
1. If I connect a speaker to the output 1, no hum.
2. If I connect a speaker/microphone to the intercom station no hum
3. When I connect the Output 1 with line level converter I get a loud hum
4. If connect a tone generator to the input of the line level converter, I get a quiet tone through the intercom, but no hum

I'm assuming that I must have a ground loop issue? Can someone give me suggestion to resolve the hum?

Thanks,
Rob

 

[BraveSirRobbin]

I believe the problem may be related to the fact that the output referenced in that schematic for the pre amp output is NOT tied to any ground associated with the Elk itself (continue reading the posts in that link).

I would first take a set of headphones and see if the hum is coming from the preamp output without anything connected to it. If it is, well, at least you know that is where the hum is coming from.

I did a bandaid fix and messed with the elk volume output and the input to the pc (I think, been a while) to minimize the hum while there were no voice announcements coming from the Elk (it wasn't really noticed during an announcement).

 

[project_x]

It has no hum with the headphones on the line converter output.

It appears that it I disconnect the wires from the speaker, and measure to the intercom ground, there appears to be +15V on each of the wires that connect to the speaker.

What is the best way to handle this, I can't pull the neg. side of the speaker. to ground (I don't think)? Can I isolate the two systems from each other, so this is not an issue?

 

[BraveSirRobbin]

Do you have a link to some manual on what you are connecting to?

 

[project_x]

Not at all, here is theinstallation manual

I'm thinking about trying to use a 4N35 or something similar to separate the two systems.

 

[project_x]

I took the output of the Elk Output 1, and used the divider circuit as the input to a 6N136. I used the +15V from the intercom as Vcc and tied the ground of the intercom to the Gnd of the 6N136. I then used the Vo connected to the + side of the speaker.

Works perfectly, no pop, no hum....

 

[project_x]

I took the output of the Elk Output 1, and used the divider circuit as the input to a 6N136. I used the +15V from the intercom as Vcc and tied the ground of the intercom to the Gnd of the 6N136. I then used the Vo connected to the + side of the speaker.

Works perfectly, no pop, no hum....

Does anyone have any idea what the impedance of the voltage divider/line out circuit referenced on the elk site? Can i put one of the elk speakers behind my keypad in parallel with the line out?

 

[Spanky]

Does anyone have any idea what the impedance of the voltage divider/line out circuit referenced on the elk site? Can i put one of the elk speakers behind my keypad in parallel with the line out?

It should be about 600 ohms. An 8 ohm speaker will kill it.

You can disconnect the audio line from your intercom when not using it through a double pole double throw relay and write a rule to close the relay contacts when the audio amplifier turns on an some voice is playing.

WHENEVER audio amplifier turns on
Then turn on output xx

WHENEVER audio amplifier turns off
Then turn off output xx