My 1984 Apencade has developed a problem with very low radio volume in the headsets. The fairing speakers work normally and the mute button works fine also. Trying 3 different headsets all have very low volume, but will get much less if the mute button is activated. The intercom also has very little volume. Wiggling the plug pigtail has no effect. I am open for suggestions. I see an amplifier listed. Does this work on the fairing speakers?