My problem might not actually be a problem but I would like some advice to know if what I've done is wrong or improper and if it was the cause of the problem. This situation is this: While learning to do setups myself (I have minimal experience with fixing/repairing basses), I noticed that my G-string was buzzing at the first fret so I put in a shim by just prying up the nut (nut was still glued in, did not remove the nut) and sliding in a short piece of thin cardboard. The piece is only maybe half of the length of the nut or less and is resting under the G and D strings. I put on a new set of strings and everything seemed good to go. The fret buzz I was trying to get rid of was gone. It wasn't until later that I noticed my A-string was sounding much weaker than the other strings. At first, it seemed like it was just the open string that sounded quieter and fretted notes were ok. Other times I felt that any notes on the A-string were quieter so I couldn't quite determine where the issue was. This lead me to believe that there was either something wrong with the nut shim job or the string was just a bad string. So now I've put on a new set of strings and am trying to figure out if the problem was the string or the nut. With the new strings, I think the fretted notes sound fine but now I cannot really tell if the open A is the same volume level as the other strings. I feel I can't trust my perception because in my mind, I'm looking for the volume to be quieter because I have doubt in my mind that I did an acceptable job on the nut shim. Other times I think the new string sounds fine and I am just being paranoid about it and there is no problem with the nut, it was just a bad string. In my mind, I am thinking that the nut underneath the A-string is not making full contact with the neck and this is somehow dampening the vibrations. But then again, it might be fine and I am just looking for a problem that isn't there anymore. So basically, I would like to know if you think what I did to shim the nut is wrong and was/is the cause of the problem, OR the nut shim is fine and it was just a bad string and I no longer have a problem. I can't really tell if I still have the problem or not because I feel like I am looking for the problem and it might not be there anymore. Also, it is not the pickups, I could notice the problem when it was not plugged in. Sorry if this is long and confusing. I just want to try to make some sense of the situation. Thanks for any advice!!!