Connect xtl1500 to a Bogen Amplifier in a building

spuddy98 · Feb 8, 2018

I work for a fire department. We have several stations with their own PA amplifiers. I want to cleanly connect our XTL1500 motorola radios that we use as monitors to the system. The radio has a base with a speaker connected to it.The radio is currently connected to the amp in a "rube goldberg" system by the dealer. They have a black and yellow wire that come out of the rear connector to a BOGEN WMT1A on the center terminal and a side terminal with a resistor connecting between the two. Then it is tapped into an existing wire that also feeds from a leased telephone line for a PA system. This wire then plugs into a MIC 1 input using a 1/4" phono jack with some resistors in it set up maybe as a voltage divider??

Any help is appreciated.

cmdrwill · Feb 8, 2018

Use the Filtered Audio output on the accessory connector. It is Line Level and not affected by the volume control.

spuddy98 · Feb 8, 2018

I've been reading your posts. So I can just connect it to a line level input on my Classic C35 Bogen amp and be done with it. No capacitors and No resistors?

Next question: Cmdrwill, do you know anything about using leased lines (phone lines) and the bogen wmt1a amplifer for 600 ohm. I'm sure you will say its really simple. One of our lines is really picking up noise/phone calls/radio stations.

Thanks

MatRat80109 · Feb 9, 2018

I was tasked with updating a 1960's era amplifier / speaker system a few years ago. I got a Bogen HTA-250A amplifer. When replacing the Spectra dash mount radio with an XTL5000 I searched for a cleaner solution. All I had available were remote (trunk) mount radios.

In the new setup the radio is in a HLN6042 speaker tray and powered by DC power supply. The remote bracket is velcro'ed on top of the radio. On the remote I used the HKN6187 cable which gives 2 standard mini headphone outputs. I think they are 2.5mm. I have a cable from one of these jacks to the RCA HI-Z input of the amp.

The audio level is fixed and independent of the front volume knob. There is no DC Hum that the old system had due to being connected to the radio speaker connector and no crazy filtering capacitors needed. Normally I have the remote volume all the way down. When monitoring, the remote's volume knob adjusts the tray speaker without affecting the amplifier / speaker system.

This has worked great! Upgrading the radio to an remote mount APX6500 was simple.

MR

bharvey2 · Feb 9, 2018

I'm not familiar with the outputs on your Motorola radio but I've connected up a number of Bogen amps. Though I might be understanding your description of the wiring, I think your correct in your assessment of a voltage divider circuit being used to drive the amp. Cmdrwill states that your radio has a line level out. If that's the case you should be able to drive the high impedance input of your amp directly. If it's a true Line Level then it should provide a strong signal to your amp input.

spuddy98 · Feb 9, 2018

I tried it today on our new amp and it didn't work correctly. The sound was garbled. I need to verify the amp is working correctly before I spend time on the radio "test-test, 1-2-3-4-5,5-4-3-2-1" with the whole county listening. I did notice if I switch the input wires it would change the hum...

spuddy98 · Feb 9, 2018

I did remove the rear connector only to see what pins are involved and found it has the speaker pins - of course as they are connected to a speaker. It has the ignition sense pin, a "reset" and filtered audio with two ground pins. I'm thinking maybe my problem is the new Bogen Amp. I will investigate more monday.

cmdrwill · Feb 10, 2018

IS the amp connected to the speaker pins? The speaker output has DC voltage on it that may affect the amp.

Try connecting the Filtered audio pin along with ground pin into the amp on a LINE input.

Filtered Audio LINE Input

Ground Ground

Then set the LINE level on the amp and fix the knob so it does not get changed. Put a 'nail in it' !

spuddy98 · Feb 10, 2018

I connected it exactly as you describe. I need to verify this new out of the box bogen amp is good. On the output to the 70 volt speakers there is a connection labeled "common" and one labeled "ground" they are connected with a removable jumper could this be an issue. As I say, I will probably try the connection with the old amp first and connect the new amp somewhere I can test it privately.

Project25_MASTR · Feb 10, 2018

spuddy98 said:
I did remove the rear connector only to see what pins are involved and found it has the speaker pins - of course as they are connected to a speaker. It has the ignition sense pin, a "reset" and filtered audio with two ground pins. I'm thinking maybe my problem is the new Bogen Amp. I will investigate more monday.

Should have emergency jumped to ground (function can be disabled on APX but not XTL). Ignition is fairly standard (though it can be bypassed in programming).

spuddy98 · Feb 12, 2018

I was able to reconnect the Bogen Amp to the radio in the way described by cmdrwill and it worked fine. I believe on friday I had a stray wire contacting the wrong location. My assistant also connected our PA that runs through leased lines to this amp using the phone in line that will mute the Radio on the AUX channel when the PA is used. It works like a dream. We eliminated a great deal of junk and now plan on moving on to other stations with issues hearing the dispatch information. Thanks for all of your input.

Connect xtl1500 to a Bogen Amplifier in a building

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