Never had any problems. I play whatever comes up. To power the talkbox I use a Vox pathfinder 15 guitar amp. It's a great effect but as with any effects, I like to use it as little as possible so the bass can do it's job. Over the years I have used it with a variety of amps and of course a Les Paul Custom.
Sound quality depends on who's using it.
I have to change the tube out every once in awhile. Well, I just can't beleive only one person has submitted a review on the Heil Talkbox since my own. Perhaps talkbox interest is waning. Or everybody is buying Rocktron Banshees. Wait a minute. . .