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Connecting a vintage microphone to a PC

Discussion in 'General Electronics Discussion' started by Richard9025, Oct 21, 2017.

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  1. Richard9025

    Richard9025

    205
    7
    May 24, 2016
    Hi!
    I recently got this microphone, a turner plus three american cb microphone from 1975.
    [​IMG]
    (photo from the internet)

    Specifications are in this pdf: http://www.radiomanual.info/schemi/ACC_microphone/Turner_+3_user.pdf
    It has a preamp inside that is fed from a 9V battery.
    Can I just grab a 3.5mm jack and adapt it to the jack that it already has using the following image?
    1. Signal input (tip) [​IMG]
    2. +5V bias (ring)
    3. Ground (sleeve)
    I just connect the signal input and ground to the 3.5 microphone jack, I don't need the 5V because it already has a preamp. Isn't that it so?
    Thanks!
     
  2. ramussons

    ramussons

    357
    66
    Jun 10, 2014
    * Tip and Ring need to be connected together; its a MONO mic
    * The unit will over drive the MIC input to the PC; use the Line IN if available.
    * If Line IN is not available, you will need to Attenuate the MIC output.
     
    Richard9025 likes this.
  3. AnalogKid

    AnalogKid

    2,371
    661
    Jun 10, 2015
    Based on the datasheet, yes. If page 4 really is the internal schematic, then this mic has a compressor or AGC (automatic gain control) circuit to even out changes in loudness caused by turning you head away of becking away from the mic.

    ak
     
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  4. Richard9025

    Richard9025

    205
    7
    May 24, 2016
    Yes, that's it. This is another, much clearer version of the schematic (they're both the same).
    schematic (1)-1.jpg

    Its jack looks like this
    [​IMG]
    I can test using the continuity function of my DMM which pin is the audio out and which is the ground of the microphone.
    Then I can connect them to the 3.5mm pink jack that looks like this
    1zP76.jpg
    .

    Tip and ring or ring and ring? the above pink 3.5mm microphone jack is a TRS type (only mono microphones), shouldn't the audio out of the mic connect to the tip, ground to the sleeve and the ring be left alone as it outputs the 5v for the preamp, but my mic already feeds from a 9V battery so it doesn't need any additional voltage?

    [​IMG]
    That's what I'm fearing, overdriving the soundboard. It has a blue LINE IN jack, a green AUDIO OUT jack and a pink MICROPHONE IN jack.

    Also, should I change the electrolytics? it has quite some, they're from '75 and they have odd values like 5, 20 and 30.
    Thanks!
     
    Last edited: Oct 21, 2017
  5. Audioguru

    Audioguru

    2,872
    644
    Sep 24, 2016
    The microphone input on a pc is designed for an electret mic which is a condenser mic with its 48VDC stored permanently in its electret material. The mic has a Jfet impedance converter inside that must be powered with the +5V on the mic jack. The current is very low, about 0.5mA.

    Your antique mic's preamp will not work with the very low current from a mic jack so power the antique mic with a 9V battery and feed its audio output to a blue line input on the pc. It will probably sound awful.
     
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  6. Richard9025

    Richard9025

    205
    7
    May 24, 2016
    I adapted its jack to the standard 3.5mm jack and I connected the mic to the line in input of the sound card.
    Results: Very good and clear voice reproduction! It's very sensitive and because of its low frequency response (300-3500 Hz), others think that I'm talking in a walkie-talkie:) !
    Many thanks for all of your support!
     
  7. Audioguru

    Audioguru

    2,872
    644
    Sep 24, 2016
    How can a microphone that cuts off the important consonants sounds in speech create clear voice reproduction?
    Consonants easily reach 14kHz and without them speech is just vowels with no meaning.
    Half of a telephone or walkie talkie conversation is, "What did you say? (Six, or fix)?"
     
  8. ramussons

    ramussons

    357
    66
    Jun 10, 2014
    If that mike specs served the communication requirements of that day and today it cannot, it only means that the human hearing capability has deteriorated over time. :D:D:D
     
  9. Audioguru

    Audioguru

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    Sep 24, 2016
    When people are communicating on a system that cuts high speech frequencies like most consonants have, then to be understood they must repeat what they say over and over and use synonyms like Charlie, Foxtrot and Zebra to replace saying the letters C, F and Z. Words beginning with S like Six get confused with words beginning with F like Fix, and many other letters and words.

    Hearing has deteriorated over time? Of course, high frequency hearing loss is completely normal for old people. Maybe old people designed the telephones and radios that cut high frequencies because these old engineers could not hear high speech frequencies.

    When I was 69 years old I went for a free hearing test. It showed that my loss of high frequencies was normal for my age and my "speech recognition" was pretty bad. Hearing aids were programmed to correct my high frequency hearing loss, they improved my life tremendously. They also improved my "speech recognition" score tremendously.
    I like music again. My hearing aids have selectable modes that normal hearing cannot do like extra sensitivity, muting, compression, changing directivity and noise reduction. They also have a "music" mode that I use often that has none of the tricks and is linear.
     

    Attached Files:

  10. AnalogKid

    AnalogKid

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    661
    Jun 10, 2015
    For speech recognition, high frequency perception is overrated. POTS (Plain Old Telephone System) has a brick-wall bandpass of 3.3 kHz to 4 kHz (it varies among individual systems). And yet, people can interpret not only speech, but the emotion in a voice. And remember, the phone was invented by a speech and hearing therapist; he was trying to invent a hearing aid.
    Ah, the good old days...

    ak
     
  11. Audioguru

    Audioguru

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    644
    Sep 24, 2016
    I am re-living my good old days because I am feeling younger every year I get older. After surviving a heart attack 8 years ago and watching the doctor put stents in my blocked heart arteries, I exercise much more, eat better and feel great.

    I also was blinded with cataracts (old age). I watched as the doctor removed the original foggy lenses in my eyes, replaced them with synthetic lenses and did surgery to make my eyes perfectly round (they developed astigmatism due to age). Now my vision is much better than in my good old days.

    Of course I am retired and am living off a pension and my investments so every day is a Saturday and I do whatever I want whenever I want.
     
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