Using Studio Microphones On Icom Radios

Discussion in 'Ham Radio Discussions' started by K5FRH, Feb 28, 2019.

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  1. K5FRH

    K5FRH Ham Member QRZ Page

    It appears that yesterday's discussion was deleted, not sure why. However, I wanted to post this question.

    Would it be possible to remove the preamp from an existing Icom hand mike and install it in some small enclosure so that it could be used with so=called "studio mikes" ie. Shure SM 58, SM 57 and others.

    I was thinking I would like to build an in=line adapter using a short pigtale with the appropriate Icom connector on one end for the radio, the preamp in a small box, then a pigtale with a female XLR connector - allowing me to plug in a variety of mikes and use the Icom mike preamp to adapt the levels.

    Thank you for your opinion.

    Rod, K5FRH
  2. AB2YC

    AB2YC Premium Subscriber QRZ Page

    I didn't realize Icom used preamps in their hand mics, I thought they just used electric condenser mics.

    I would think it would be easy to just build a small preamp in a box for use with dynamic mics.
  3. K5FRH

    K5FRH Ham Member QRZ Page

    I have not dissassembled a mike, but I have been told both ways - electret element and also preamp. Maybe different mikes different ways.
  4. KC8VWM

    KC8VWM Ham Member QRZ Page

    An electret condenser mic element contains a built-in FET transistor which provides amplification.

    I guess some people are calling that a hand microphone with a built-in pre-amp?

    Last edited: Feb 28, 2019
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  5. K5HS

    K5HS XML Subscriber QRZ Page

    I am using a Heil PR40 with my Icom 7100 through its adapter cable with no pre-amp.

    Previous to the simple setup I ran through a rack of audio processing gear, but the tx bandwidth is 100-2900 so no real gain was seen.
  6. AA1PR

    AA1PR Ham Member QRZ Page

    there also needs to be a tantalum capacitor in line with I think its the 8v line so you dont burn the rig out

    do your research, I remember the aftermarket 3 pin din cable I bought had such built into it
  7. KC8VWM

    KC8VWM Ham Member QRZ Page

    The voltage on an Icom rig is not present on any mic audio lines unless you intentionally put it there from pin #2

    So If you want to do a dynamic studio microphone, you simply wouldn't include pin #2 in the wiring configuration.
    Last edited: Feb 28, 2019
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  8. KA4DPO

    KA4DPO Platinum Subscriber Platinum Subscriber QRZ Page

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  9. KA4DPO

    KA4DPO Platinum Subscriber Platinum Subscriber QRZ Page

    Sorry for the big picture but I would not re-size for some reason. Anyway, on all of the older Icoms there is 5 volts between pin one and pin seven, which are also the mic pins. Putting a 1 uf cap in series with pin one effectively blocks the DC voltage so that a non amplified, low impedance microphone can be used. Here is the hand mic from my IC-740. I have used this circuit in other mics and it really works well.

    On my IC-7600 pin 2 does have plus 8 volts on it, I don't know when they made the change but unless you have a newer radio it's probably a good idea to make sure there is no voltage between pin one and ground.

    Last edited: Feb 28, 2019
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  10. K0DD

    K0DD Premium Subscriber QRZ Page

    At our last station we utilized a Shure KSM27 as the microphone. That mic utilized Phantom Power. I was looking for a more wholesome warm tubesk type of audio... So installed a tube preamp, parametric equalizer, Compressor and noise gate. The input of the unit provided the Phantom power the Mic was looking for. THEN the output of the Compressor Equalizer was ran in through the Rear Panel Audio input... That bypassed a lot of the 7800's circuitry.

    Shure You can use a Shure on your Icom, but I wouldn't just plug it in... The Phantom power is much higher voltage than anything provided by the Mic jack on any Icom. Have fun...

    Erika DD
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