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Thread: blocking capacitor for audio amp for TRS-80

  1. #1
    Join Date
    Dec 2016
    Location
    Ridgetown, Ontario, Canada
    Posts
    80

    Question blocking capacitor for audio amp for TRS-80

    Fast question: what would be a good size blocking capacitor for a auto amp to connect to the cassette output of a TRS-80 model 1, or 4?

    I'm thinking 1uf with the negative terminal facing the amp.

    I'm using a pre-made amp I bought from ebay for a couple dollars, running a 7805 voltage regulator to keep it at a safe voltage, driving a 4ohm 3watt speaker from an old pair od Creative Labs speakers. So the blocking cap is just a protective layer between the TRS-80 and the amp..
    ///
    TRS-80: Model 1 w/IE, Model 4 w/128K, PC4
    Atari 800 and 800XL

  2. #2
    Join Date
    Aug 2013
    Location
    Philadelphia,PA area
    Posts
    84

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    The Radio Shack Mini Amp uses a 4.7 uF/25V cap with the positive connected to the amp.

    http://www.repeater-builder.com/radi...-schematic.gif

    HTH,
    Tom

  3. #3
    Join Date
    Dec 2016
    Location
    Ridgetown, Ontario, Canada
    Posts
    80

    Default

    Thanks! That's perfect since the amp I have is based on the same IC.
    ///
    TRS-80: Model 1 w/IE, Model 4 w/128K, PC4
    Atari 800 and 800XL

  4. #4
    Join Date
    Dec 2016
    Location
    Ridgetown, Ontario, Canada
    Posts
    80

    Default

    A few photos of the finished speaker with amp installed..

    Power input goes to fully wave bridge and 2200uf capacitor and a 7805 voltage regulator, and auto input goes though a 4.7uf capacitor and then goes to the amp board mounted in the front of the case. using the full wave bridge gives an idiot proof power input, AC or DC 7 to 15 volts.

    Also has both RCA and 1/8" jack for audio input.
    Attached Images Attached Images
    ///
    TRS-80: Model 1 w/IE, Model 4 w/128K, PC4
    Atari 800 and 800XL

  5. #5
    Join Date
    Aug 2013
    Location
    Philadelphia,PA area
    Posts
    84

    Default

    Looks good!

    Tom

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