The Heil Goldline GM4 mic created specifically for full-range smooth articulate SSB audio with a wide 60Hz-16kHz response.
A +4dB peak @2 kHz gives the new Goldline microphone excellent voice articulation along with it’s “big bottom” low end
that is all so important for producing a well balanced studio quality SSB signal.
This microphone is a discontinued Heil product.
The Heil Goldline GM4 is equipped with a full-range (broadcast) mic element and the famous DX Dream Machine HC-4 element.
I assume that you are using the CC-1-I adapter cable for your Icom IC-756Pro II ??
It sounds like that the full-range element in your GM4 ... has failed.
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Send product (shipping prepaid) to:
5800 N. Illinois St.
Fairview Heights, IL 62208
Please call the Heil Sound Service Department at +1 (618) 257-3000 Monday-Friday 8:30 AM - 4:30 PM (CST) -- if you have questions.
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