Open strings Flat after Replacing Nut

[bjlevine]

I had a cracked nut which I recently replaced with a nut that looked identical. Now after I tune it up, if I tune it to open strings, its sharp on all the fretted notes, and if I tune it to the 5th fret, its flat on the open strings. Obviously something is wrong. Any suggestions?

[2400]

I'm not the expert in these matters, but it sounds like the new nut has changed the intonation slightly. Correcting it at the bridge end should solve it.

[bongomania]

^^^ Sounds right to me.

[DrewinHouston]

If the nut is in the wrong place, the open string intonation will be off and no bridge correction will fix it completely. It would be like moving one of the frets. It sounds like the new nut is too far from the first fret, you may have to replace the nut again.

[lug]

If the nut is not cut deep enough, the fretted notes will be slightly sharp compared to open notes. The slot depth should allow the string to be just barely higher off the fingerboard than a fretted note allows.

[9mmMike]

Originally Posted by 2400

I'm not the expert in these matters, but it sounds like the new nut has changed the intonation slightly. Correcting it at the bridge end should solve it.

That would have been my thought as well. Assuming the position of the nut has not changed but perhaps the height is a little different.

[bjlevine]

Originally Posted by 9mmMike

That would have been my thought as well. Assuming the position of the nut has not changed but perhaps the height is a little different.

It appears to be in the same position. So you're saying I should adjust the bridge height, or should I move the position of the saddles?

[bongomania]

Just re-do the intonation for all strings, which is mostly about moving the bridge saddles, but also affected by saddle height.

[dystopiate]

Nuts should be cut a little deeper on the tuner side, more shallow on the fretboard side. Maybe it's a lefty nut on righty bass or vice versa? That would lengthen the speaking length of the string causing it to be flat when open.

[Chasarms]

It seems odd that the changing of the nut would throw off the intonation if it was properly installed.

If you installed the nut out of plum or if the slots are not correctly angled, it is possible that the strings are witnessing on the back edge of the nut only. This would create the symptoms you describe.

However, the most common cause of these symptoms is the nut is too high. If the slots are too high, the strings are traveling too far in order to cleanly witness on the fret, and you are, in effect, bending the fretted notes sharp.

If these symptons are the most pronouced at the first fret, it is probably as others and myself are suggesting, the string slots are too high.

[bjlevine]

Thanks for all the advice. I'm fairly confident in the installation, though not necessarily that the nut itself is identical to the one I replaced. I guess I'll try all of the above, starting with the least destructive.

[9mmMike]

Originally Posted by bongomania

Just re-do the intonation for all strings, which is mostly about moving the bridge saddles, but also affected by saddle height.

What he said.

[JTE]

You can't just toss a nut in. You'll have to file the slots to the correct depth for YOUR particular chunk of wood. Read through the entire set-up in the stickies, and do a proper set-up. You can't correctly set intonation if the nut is wrong. But then, MOST nuts are wrong because they come from the factories cut too high.

See, to correctly cut a nut slot, you need to spend a lot of time. And, if you go just one pass of the file too many, you have to start over or shim the nut. So, it's a cost saving move if the production leaves the nut a little too high, counting on the store to do it correctly. But since most stores have no idea what a correct set-up is anyway, that hardly ever happens.

John

[ehque]

Originally Posted by JTE

You can't just toss a nut in.

+1.

Just because it's got string grooves cut into it doesn't mean you can just slap it on and expect it to work. You need to make sure the slots are cut to the proper depth.