A string appears to be having issues with the nut.
 

Notably staying inside of it... :crying:

I have a TBC AP-400MM. A couple of weeks ago I decided to switch the factory strings for a set of Roto 44s. I thought I must have cut the A too short, because it kept popping out of the nut under any force over light plucking. I lengthened it with another piece of string and it made it a little better, but I wasn't a huge fan of the Roto's anyway so I switched to DR Back Beauties today. The problem is persisting! I can manage plucking but any attempt to use a pick is a problem. I don't think I cut the string to short; it looks like it's wrapped as far to the bottom as it would go... The angle isn't any different than it was with the factory strings I don't think... I haven't altered the nut...

So, any have any ideas? I'm fresh out.

Here are some pics of the tuner and nut in question:

The string on the tuner:


The angle from that tuner to the nut:


The nut with the string popped out:


So yeah, anyone think they can help with my nut problems? :D

Looks like your going to need another string tree to put more angle on the A string.

Really? I've only seen A's going through trees on fivers and sixes, but if it solves the problem....

Just get it all the way down. It may be fine.

A lot of Yamaha and other inline 4 head stocks have them, also look at how most of the 4 string MusicMan basses have them for the A and D because the E and G are closer to the nut and the downward angle is increased.

Or you can try wrapping the whole length of the string on the tuner post and see if it will push it down far enough.

It looks like the nut isn't cut as deeply for the A as the other strings, unless it's just the camera...

Insufficient break angle on the A string for whatever reason. Your final "exit" wrap should be almost touching the ferrule or retainer nut. Do you have an old string cut to the proper length for comparison? A strings are particularly problematic given the headstock geometry and is a frequent topic of discussion here on the forum. You may want to clean up the nut slot but, overall, the cut looks fine. As a general rule, string retention is maintained by the aforementioned break angle and, when done properly, eliminates extraneous BS such as rattles, buzzes, etc.

Edit: a second glance at the photo shows that you more-than-likely have enough string-wrap to slide downward on the tuner post. Try that first....it's cheaper than adding a string retainer.

Riis

Look closely and see if the string is seating properly in the nut slot. That particular string might be a tad too thick.

Tie it down with a bit of string and forget about it.

Thanks guys, you've been a great help. I rewrapped the string trying to get it as low as possible, and it seems to have worked- Barely. I really need to try if I want it to pop out now, could be a problem if I get carried away at a gig or something but for now it'll be stable. I'll make sure I cut the strings longer from now on, I didn't know they were supposed to go down that far. But yeah, thanks. :)