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Yamaha CM-500 Headset & ICOM IC-9700 - No Mic Output?

Discussion in 'Microphones, Speakers & Audio Processing' started by K4EI, Sep 17, 2019.

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  1. K4EI

    K4EI XML Subscriber QRZ Page

    I recently upgraded the VHF/UHF part of my station with an ICOM IC-9700. The IC-9700 is the VHF/UHF brother to the much-heralded IC-7300 and the two rigs share many design aspects. I presume the mic circuitry is identical and so my question could as well apply to the 7300.

    Which is...

    I own three headsets... a Heil Pro 7 w/dynamic mic element (used on my Kenwood TS-590SG), a Heil Pro Set w/IC electret mic element (sold by Elecraft and used on my KX3), and a Yamaha CM-500 (vintage, one-year-old) w/electret mic element (also used on my Elecraft KX3).

    Wanting to be able to use these three headsets with my new ICOM rig, I purchased the Heil AD-1I and Heil AD-1IC adapters.

    The AD-1I includes the DC blocking capacitor and (I thought) was for interfacing dynamic mics with ICOM rigs.

    The AD-1IC does NOT include the DC blocking capacitor and (I thought) was for interfacing condensor/electret mics with ICOM rigs.

    Alas. My Heil Pro Set headset, using the AD-1IC adapter cable works fine. Phone works, mic works. All good.

    But curiously, neither my Yamaha CM-500 headset, using the same AD-1IC adapter cable nor my Heil Pro 7 headset, using the AD-1I adapter cable, work. In both cases, I get phone (audio in my ears), but no mic output. Changing mic gain has no effect.

    Any ideas?
  2. W1VT

    W1VT Ham Member QRZ Page

    I have a CM-500. It has a little battery box for powering the microphone if you can't figure out how to get the radio to provide power.

    "The Heil Sound iC electret microphone element has been made to utilize bias power in iCOM radios which addresses low-gain issues that arise when using dynamic elements."
    The Heil advertising suggests that their dynamic mic may not provide enough signal for some Icom radios. Did you try turning the mic gain way up when using the dynamic mic?
  3. AB4M

    AB4M Ham Member QRZ Page

    Did you ever get the Yamaha CM-500 to work as a mic? I just received a Yamaha CM-500 to use with my IC-7300 and have the same issue using the Heil AD-1IC adapter, I can hear and PTT but no audio from the microphone, with or without the battery box.

    I thought the Heil AD-1IC was the correct adapter for the IC-7300.

    Any help is appreciated.
  4. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    The CM500 mic plug is stereo, at least mine is. Could it be that the adapter assumes a mono mic plug so it isn’t making contact correctly?
  5. K4EI

    K4EI XML Subscriber QRZ Page

    Hey, Mark. Alas, no, I never did get my CM-500 headset working with my IC-9700. When the Heil AD-1IC adapter didn't work, I also tried the AD-1I (which includes the blocking capacitor, necessary when using a dynamic mic element). That adapter shouldn't work... and it didn't.

    So don't know what to tell you. I didn't spend an awful lot of time on it... just went back to using the Heil Pro Set headset, using the AD-1IC adapter - and that works a peach. I'd rather use the CM-500 - as Tx audio quality is about equal between the Heil Pro Set and the CM-500, but the Yamaha headset is more comfortable.

    Bob (N0TZU), that's a good thought regarding stereo-vs-mono. Alas, that's not what it is... the phone jack on both headsets is stereo, but only the Heil Pro Set works.

    It's a curious anomaly.
  6. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    Interesting, I can’t imagine why it would work with one headset and not the other. I had no issues with the CM500 on my K3, plugged into the rear 1/8” jacks for that purpose, no adapter. I’ll look up the circuit in the radio and post it, maybe the pin out on the CM500 is different from Heil.
  7. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    @K4EI, I finally had some time and looked at the schematic of the rear K3 microphone jack, and only the tip and sleeve are used; ring is open (tip is bias and mic+, and sleeve is mic- and ground). I also determined with an ohmmeter that tip and ring on my CM-500 mic plug are shorted together. So it's very simple and the CM-500 should work with your adapter as long as contact is being made correctly to tip and sleeve.

    At this point, I would insert an unused stereo plug into the adapter jack, bring out the leads, and measure the voltages to find out what is being put on sleeve, ring and tip. Also, I would check the CM-500 mic jack to verify that the connections on yours are the same as mine.
  8. K4EI

    K4EI XML Subscriber QRZ Page

    Bob, you were right all along. It's a mono-vs-stereo problem... the Heil Pro Set is mono; the Yamaha CM-500 is stereo. Has to be mono. A 3.5mm stereo-to-mono adapter squares it away.

    Thanks, my friend!
    N0TZU and KJ4VTH like this.
  9. AB4M

    AB4M Ham Member QRZ Page

    Hi Bob and Jeff. As an FYI, I ordered a stereo to mono adapter and now my CM500 headphones are working perfectly with the IC-7300, no battery box needed. I am getting good audio reports but also am figuring out the best COMP and Mic Gain settings. So far a couple folks have worked with me and said it sounds best with Mic Gain around 40% and Comp at 2%, that was on 80m ssb.

    Thanks again for the help. These Yamaha CM500 are very nice with the IC-7300.
    K4EI and N0TZU like this.

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