Two radios, One speaker

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=43934
Printed Date: May 15, 2025 at 11:56 AM

Topic: Two radios, One speaker

Posted By: wheelman
Subject: Two radios, One speaker
Date Posted: November 27, 2004 at 9:46 PM

Howdy,
I have an Yaesu FT-7800 (2-way radio) and a Uniden BCT8 (scanner) in my car. I also have a Motorola extension speaker. I would like to use the speaker for both radios. I am wondering if I should isolate the speaker outputs for the two radios, or if I could just hook them together and then to the speaker.
Thanks in advance.
JJ

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Hang on boys... we're going in hot!

Replies:

Posted By: hotwaterwizard
Date Posted: November 28, 2004 at 12:24 AM

It would be better to use an Isolation Transformer to hook them together.

You can find one in a good RCA adaptor that converts a Stereo to RCA

Just rewire it for your project.

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John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !

Posted By: hotwaterwizard
Date Posted: November 28, 2004 at 1:10 AM

Here is the RCA adaptor I am talking about.

posted_image

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John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !

Posted By: hotwaterwizard
Date Posted: November 28, 2004 at 1:28 AM

Here is your final circuit

posted_image

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John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !

Posted By: hotwaterwizard
Date Posted: November 28, 2004 at 2:09 AM

You could use the RCA Adaptor to make the Audio at low level, Then you could Use an Audio Mixer Circuit then send it to one Amplifier.

posted_image

https://www.electronics-lab.com/projects/audio/034/ posted_image

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John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !

Posted By: rknj01
Date Posted: November 28, 2004 at 2:18 AM

i would just use 2 relays

Posted By: hotwaterwizard
Date Posted: November 28, 2004 at 2:23 AM

rknj01 wrote:

i would just use 2 relays

He wants to hear both at the same time thru one speaker.

How would a relay do the job?

We don't want the output of one Radio to Feed into the output of the other because it could blow the Audio amplifier. So you have to Isolate the two from eachother then combine them into one.

The simple solution would be to use a small Dual Voice coil Speaker or a second speaker.

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John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !