DIY Intercom Design Thread
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Thread: DIY Intercom Design Thread

  1. #1

    Default DIY Intercom Design Thread

    Hey guys. So I have been bored lately and decided that I want to make a new intercom for my car.

    I made one a long time ago, and it was using transistors for the preamp on the input stage. After about a year of use, I ended up having to replace the transistors from being peaked out too much.

    Here are photos of the old one:

    Link to download files for old intercom:

    So I'm wanting to make a new one and trying to only use integrated circuits that way it will be very robust and wont break down as fast. Also it will have better clairity in the sound.

    At this point I am planning the intercom to have:

    - Input and output for both driver and co-driver.
    - Be compatible with Terratrip mic/headphone.
    - Input for a HAM radio, this connection will be isolated with an audio transformer. Gain will be set internally.
    - Output for a HAM radio, gain will be set internally.
    - Audio Compression with one "knob" for controlling threshold, all other parameters like attack, release, gain and compression ratio will be preset and not adjustable.
    - One 5 LED VU meter for volume.
    - High quality Mic Preamp
    - 1.5W Output Amp for the driver and co-driver channels.

    I'm thinking of designing a squelch system into it, and also having volume set by Digital Pots, instead of using manual pots with the knob. The digital pots will have push buttons for volume (like the Peltor) instead of knobs (like the Terratrip).

    I'm not planning on selling this, just making a schematic for it and maybe a run of boards so us DIY electronics nerds can have a intercom that we built ourselves.

    Is there anything else you guys could think of that you would want in an intercom?

    Drew Brashler
    Last edited by Yesitsdrew5310; 07-25-2012 at 07:31 AM.

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  3. #2


    (saved for final project schematic)

  4. #3


    (saved for final project pictures)

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  6. #4
    Uh Oh, UH OH, UHH OHHH!!! johnhuebbe's Avatar
    Join Date
    Dec 2004
    St. Peters, MO, US.


    I'm interested.
    Behold the POWER of cheese!
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  7. #5
    100 oversquare right bentmettle's Avatar
    Join Date
    Dec 2004
    Ann Arbor, Michigan


    if you are going nuts, add an environmental mic with an output to audio output for a video camera...

    I've always wanted something that takes the in car "noise" and amplifies it to run into one channel of the video camera. Seems like if the intercom could do that and be one stop audio for everything, that'd be darn handy.

    As it is now, I had to use an audio preamp out of the Terratrip.
    Last edited by bentmettle; 06-23-2008 at 11:34 AM.

  8. #6
    worlds worst co-driver
    Join Date
    Jan 2007
    Toronto/Hamilton Ontario


    If you could setup a handy mix out for video (eg ambient noise mics, like bentmettle mentioned) that would be the complete sexx0rs...

    This reminds me, I need to hook up my peltor intercom to my ham radio!

  9. #7
    L5 Lg > 4 into Broken
    Join Date
    Jul 2006
    Bethlehem, Pa


    I was thinking about designing my own a little while ago since I really don't like the Terratrips. and the one thing that I would like is seperate mic and headset volume. I've got pretty poor hearing and need the "volume" cranked on the terratrip inorder to even hear myself talk, otherwise I'm yelling pretty load and well, you don't even need a intercom at that point. The issue is that this overly increases the volume going into the drivers headset and Gus starts yelling (sometimes in spanish) that I'm making him deaf. In reality what I need is the ability to increase my mic mix for me only.

    I was thinking of using a dual pot setup. They have two knobs that share a common "shaft" so that turning the outside one turns both but the inside one can be turned alone. This would allow you to adjust the delta between the speaker volume and mic mix. Then adjust the total volume together.

  10. #8
    <catchy rally phrase> UP2MTNS's Avatar
    Join Date
    Feb 2007
    Saratoga, California, United States


    Quote Originally Posted by Jgardhouse View Post
    If you could setup a handy mix out for video (eg ambient noise mics, like bentmettle mentioned) that would be the complete sexx0rs...

    This reminds me, I need to hook up my peltor intercom to my ham radio!
    how are you doing that? doesn't peltor make an expensive thingy-do-hicky for that?
    (the other) Jon Burke
    I drive a Sub-a-rat
    Team Blog: Up Two Mountains Rally Team

    "...when it comes to racing and sushi, I never look at the bill." - Foust

  11. #9
    Kevin Welker
    Join Date
    Dec 2003
    Laguna Niguel, South OC CA


    Drew, the first iteration of the intercom you made worker pretty damn well. I'll be interested to try out the design of the new one. If it works I'll just keep the Stilo as the backup.
    Twitter: KWelkerRally
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    "You hate your car. It is meant to be destroyed and repaired. It is merely a machine that is keeping you from attaining your true top speed. Press on the skinny pedal. Turn every once in a while. Fasten your belts securely. Drive it in anger." - Don Burress - Demon Rally Team

  12. #10
    C.m.f.S. Carl S's Avatar
    Join Date
    Oct 2001
    Iron Mountain, MI.


    Output for video camera!

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