How to Replace an 8 speaker with a TRS 1/4" jack

Discussion in 'The Projects Forum' started by zombiepokla, May 13, 2009.

  1. zombiepokla

    Thread Starter Member

    Mar 30, 2009
    12
    0
    Hi all.

    I've started a project where I am using an existing toy cassette recorder circuit with no outputs.. only two 8Ω speakers. I know there is a way to replace these speakers with jacks, I have tried this once before on a toy keyboard that also utilized an 8Ω speaker.. but the jack that i installed [with no extra resistors] was REALLY loud.. If I want to replace an 8Ω speaker with a standard 1/4 inch TRS jack.. do I also need to add an 8Ω resistor in parallel with the speaker terminals or maybe two 8Ω resistors inline/in series with both the positive and negetive speaker terminals? ..or niether.

    Thanks!!
     
  2. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    If the 8 ohm output is too loud then attenuate it with a voltage divider made with two series resistors.
    Only a very old amplifier made with vacuum tubes needs an 8 ohm resistor as a load.
    A modern amplifier made with transistors does not need an 8 ohm load and will be happy driving 10k ohms.
     
  3. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    You didn't say what you're load is going to be. Are you going to be using earphones or are you feeding the audio to the input of another device? It's easier to give recommendations for the values of a voltage divider when the resistance of the load is known. ;)
     
  4. zombiepokla

    Thread Starter Member

    Mar 30, 2009
    12
    0
    thanks guys. I'm going to be running these outputs into a mixer, and then into a power amplifier. So i'm looking for a line level impedance.. I don't really know anything about impedance or "load" so if someone could give maybe a brief intro.. that'd be much appreciated. thanks for any advice
     
  5. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    Chances are a 1K/100Ω resistive divider would work for you. This would give you a 10:1 ratio without much high freq roll off.
     
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