so ive been on HF for about two years now mostly doing digital modes but lately ive been trying to get into SSB phone and honestly the audio situation is kind of frustrating. i feel like every time i listen back on my SDR or ask for reports people say im either too bassy, or the audio sounds like im calling from a tin can, or there's this low level hum that i can only sometimes hear myself.

my setup is an IC-7300 going into a Heil PR-40 through their boom arm, and i have the ALC sitting right around where the manual says it should be but i sometimes wonder if the mic gain is too high because the ALC does jump around a lot when i talk. ive played with the TX equalizer settings a bit but mostly i just left them at flat because i dont really know what im doing there.

also not totally sure if USB vs LSB even matters for audio quality on a given band or if thats a dumb question. on 40m i always go LSB because thats just what everyone does but on 20m i go USB. is there anything i can actually do to make transmitted audio noticeably better without buying more stuff, or is this just something you dial in over like years of operating

the ALC jumping around is your main problem right there. when the ALC is working hard it's basically compressing your audio in a way you didn't choose, and it sounds bad. back off your mic gain until the ALC barely moves on voice peaks, like just kissing the first couple segments on the meter. you'll probably feel like you're not loud enough but you actually will be, and the audio will clean up a lot.

on the 7300 specifically the TX equalizer can do a lot of heavy lifting. a lot of guys boost a little in the 2-3kHz range for presence and roll off some of the low end below maybe 200Hz because that's where the boominess comes from and it doesnt really help intelligibility anyway. the PR-40 is a pretty flat mic so it's not going to fight you on this. also make sure you have the speech processor off while you're first dialing things in, that thing makes bad audio worse before it makes good audio better if that makes sense.

USB vs LSB doesnt affect audio quality itself, it's just convention. 40m below 7.2 is LSB, 20m is USB, you already know the rules. that's not your issue.

yeah the hum thing would bug me too. have you checked for a ground loop? if your radio and your computer or anything else is all plugged into different outlets or power strips that can cause exactly that kind of low level hum. i chased one of those for like three weeks before i figured out it was my monitor of all things coupling into the mic cable somehow. try keying up with everything except the radio powered off and see if the hum goes away, thats usually how i start narrowing it down.