LeftyBassist.com

Weird. Not your fault Paulo but I thought that was an AC40... did Carvin make an old model called the AC30?

Are these good basses? I've always wanted to grab one of these and rip the frets out.

There are a couple of demos of them on youtube. Carvin has a fretless 5 string AC 50 in their guitars in stock section - jet black unlined fretless but w dreaded gold hardware:

http://www.carvinguitars.com/guitars-in-stock/114552

Funny, I was checking out some of those demos. It seems they're just average people demoing their basses. Unfortunately, I haven't seen or heard one yet that seems to do the basses justice. Have you Brian?

I used to have a fretless AC40 and loved it. Surprisingly fat tone. I played it live regularly in a loud hard rock band, although never as my main bass. I'd have kept it, except I eventually decided that I needed to buy backup fretted bass and couldn't afford both.

If this one were fretless I'd probably have already bought it.

I have not seen great demos on these. They are interesting though

That's an AC40.... UNLESS the 2 treble 2 bass side = AC30. I had a fretless AC40 a few years back. It was 2 treble 2 bass side tuners like this. That fretless was a great bass and played wonderfully. You could even hear it acoustically.

As far as a AC50 with a B string, I don't think you'll really be able to hear the B unless its amplified. the E was a little thin in the volume to begin with.
--> My 2 cents...

I'm pretty sure "AC30" is a typo. The two-by-two headstock is an option on most all Carvin four-string basses, so it doesn't have anything to do with the model number.

Also, Carvin's website itself says the AC40/AC50 is not intended to be played acoustically, but rather is designed as a more ideal way get an "acoustic bass tone" while amplified to gig volume. So yeah, it is unlikely that you'll get a ton of volume out of a low B string without amplification.