so this has been bugging me for about two weeks now. was having a perfectly normal qso on 40m and the guy i was talking to said my audio suddenly went kind of muffled and distorted, like i was talking through a blanket. nothing changed on my end that i could tell, same mic, same settings, hadnt touched anything in the menu.

i went through the usual stuff, checked the mic gain, the compression settings, swapped the mic cable, even borrowed a different mic from a buddy to rule that out. still sounds bad according to anyone i work. did a quick recording using the monitor function and yeah it definitely sounds off compared to what it used to be. kind of a low boxy sound with some fuzz on voice peaks.

my question is whether this sounds like it could be the DSP doing something weird or if maybe somethings going on with the TX audio path hardware side. the radio is about 4 years old and hasnt had any issues up till now. havent cracked it open yet, not sure i want to go digging around without some direction first. anyone seen this with a 7300 or similar?

had something similar happen with mine about a year ago, turned out to be a menu setting that somehow got changed, specifically the TX bass and treble in the tone settings under the set menu. i think i bumped something during a firmware update or the update reset a few values, cant remember exactly. worth checking those first before assuming its hardware because the 7300 has a ton of audio shaping options and if one of them drifts or resets it can make the TX sound really weird.

also check your microphone equalizer settings if you're using the built in one. i had mine set up pretty specifically and after one of icom's updates it went back to flat which didnt sound great with my sm-30. if you can factory reset just the audio profile without wiping everything else that might tell you whether its a settings issue or actual hardware.

if you've already ruled out settings and external stuff then yeah it could be the electret element in the hm-219 mic starting to go. those capsules dont last forever especially if theyve been around RF for a few years. the symptoms you describe, muffled and distorted on peaks, is pretty classic for a partially failed mic element. even though you swapped the mic, did you swap it with the exact same mic model or something different? different mics have different impedance and level and the 7300 expects a certain input from the hm-219 type so a random dynamic mic might not tell you much.

worst case if it is hardware in the TX audio chain you're probably looking at the AK4951 codec on the main board. i wouldnt go poking around in there unless you're comfortable with SMD work, those chips arent fun to rework. might be worth sending it to icom's service center if the warranty is out and you can't sort it with settings.