Line level in

Discussion in 'Wireless & RF Design' started by samuel.whiskers, May 26, 2014.

  1. samuel.whiskers

    Thread Starter Member

    Mar 17, 2014
    95
    2
    I'm thinking of building this circuit below, but want to use a line level input instead of a microphone. I've made an edit to the circuit, also attached. Is this the correct way to do it?? I'm not sure about the 4.7k resistor either.... Can anyone give any guidance?
    Cheers
    Lee
     
  2. #12

    Expert

    Nov 30, 2010
    16,330
    6,818
    I'd say leave out the 4k7 resistor, throw in a 10k audio taper potentiometer, and you're done.
     
  3. samuel.whiskers

    Thread Starter Member

    Mar 17, 2014
    95
    2
    Thanks - for a headphone input - the same? could leave out the pot if using volume on source?
     
  4. #12

    Expert

    Nov 30, 2010
    16,330
    6,818
    I think so. There are only a few headphones with higher impedance so I assume your, "headphone" output is designed for the low impedance type.
     
  5. samuel.whiskers

    Thread Starter Member

    Mar 17, 2014
    95
    2
    Worked well.... thanks for the tips....
    I ended up just plugging the output of a 1kHz 555 square-wave on the input there and the little transmitter worked nicely, albeit just transmitting an annoying tone over a couple of metres, but it worked.... :)
     
  6. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
    2,040
    287
    Keep in mind crystal mikes are very HOT...so you may not need much more attenuation.
     
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