Weird issue: pitch varies, sounds like two notes played together

[Mickets]

These 'beats' are heard mostly at 8, 12, 16 frets? Maybe also at 6, 18? Or even 4, 20?

They're heard anywhere on the neck, but clearer as higher up the neck (higher pitch).

Thanks

 

[Mickets]

Active or passive? If active, try replacing the battery.

Passive.

Thanks

 

[Mickets]

Are the nut slots too low? That can cause a “back buzz.” There has been a couple of threads recently on that here. For a quick and dirty test you could shim one of the slots with a slip of paper and see if that helps.

Interesting. But I don't think that's it, because no changes were made, no adjustments. The problem just gradually started, and became more evident when I removed the old strings and put new ones on.

I'm starting to think if something with the tuning gears, or the bridge not tight enough, something that's causing the tension of the strings to vary when I pluck them. Or even something with the truss rod.

We adjusted the truss rod, tightening it about 1/4 turn, and when we did that the problem improved a bit. But just a bit.

Thanks

 

[HeavyDuty]

Do you have a small C clamp? Temporarily attach it to the headstock to see if the additional mass changes things.

 

[filwitheneff]

Hello,

I couldn't find a similar issue here in the forums, so here's my post.

I have a fretless Ibanez BTB series bass, and over the last few months a problem developed: when I place a finger on the fretboard and play a note, on a single string, I hear two notes. It sounds as if the pitch of the note is varying up and down, or as if I were tuning the bass by playing harmonics on two different strings.

I make sure I press the string with my left hand finger and don't vibrate it (tremolo) and the other strings are all muted with the help of the remainder of my left hand and also the right hand (I.e.: there is definitely only one string vibrating).

The problem is more evident the further up the neck (higher notes).

I made some minor adjustments of the truss rod, pickup heights, intonation, but no change.

I changed the strings, and the problem just became more evident.

Last week I took the bass to a Luthier, which also adjusted the neck (was too lose, neck curved). It improved a bit but the issue is still evident.

It doesn't seem to be related to the neck.

I changed pickup settings (two humbuckers, switchable), and no difference.

I don't see how it could be the bridge.

I also don't see how it could be to do with the tuning gears.

Anyway, I recorded a small video, in the hope that anyone could give an idea. It's driving me nuts.

Thanks in advance!

Mickets

Video link:

I had a very similar problem...on a Fender Stratocaster. It sounded just like your video. Turned out to be pickup height. I lowered the pickups, and the problem was solved.

 

[Wasnex]

Yes, same issue unplugged. It must be something with the body/hardware...

Thanks

Ok so we have probably eliminated an electronic issue. I relistened to the video and noted something that may be relevant. Basically the same thing @Lofreck noted. With some notes it sounds like chorus. With other notes there are clear beat frequencies and the tempo of the beats seems to be related to neck position. This suggests the specific effect that manifests is related to string length.

For example you play a G harmonic (12th fret) and then fret the G at the 12th fret but slightly out of tune. The harmonic does not have chorus possibly because the string is vibrating in perfect harmony with itself, but you can hear the problem when you press the string down and the note is out of tune. At another time in the video, you play a note at the 12th fret and the chorus goes away as the note settles into pitch. Do you also hear the problem when you press the string down at the 12th fret and the note is perfectly in pitch? You may be getting sympathetic vibrations from the other strings you are not playing.

I see you have already addressed muting the string between the fretted note and the nut. I use left and right hand techniques to ensure none of the unplayed strings ring. Lay your right thumb flat across the unplayed lower pitched strings. Use your third or fourth finger to fret notes at the 12th fret and use one of your other fingers to mute all of the strings below the fretted note. Do you still have the problem? If the problem is still apparent with full muting I don't know what else to suggest.

I believe the usual suspects have been explored already: old/worn strings, twisted strings, pickup height, or issues between string height and neck relief/contour. Were your old strings the same brand and model? Did you set the witness points at the nut and bridge?

 

[Bruce Johnson]

From the symptoms I'm reading, I think you may have a small high spot down at the end of the fingerboard. It's just touching the string enough to cause a harmonic to ring.

Here's a quick test: create a little false fret. Find a little piece of small bare metal wire. Bend it to a curve to match the fingerboard radius. Put it under the strings, maybe around the 12th fret, and hold it in place by pressing down on the string right behind it. Just like it's a fret. Now pluck the string. Does the harmonic thing go away? If it does, that indicates that it is a problem with the fingerboard surface. What you've done is raise the string up a little bit, while keeping everything else the same.

A high lump at the end of the fingerboard could explain why you are still getting the harmonics even after playing with relief, pickups, and changing strings.

 

[nouroog]

Twisted strings maybe?
How did you install your strings?
I noticed that when a string is twisted along its axis when installed, it can vibrate with a weird chorus effect
Unwind a string just enough to drag the ball end between your fingers just a few millimeters away from the bridge, and make sure there is no torque.


Edit : sorry, already suggested and ruled out

 

[Mickets]

From the symptoms I'm reading, I think you may have a small high spot down at the end of the fingerboard. It's just touching the string enough to cause a harmonic to ring.

Here's a quick test: create a little false fret. Find a little piece of small bare metal wire. Bend it to a curve to match the fingerboard radius. Put it under the strings, maybe around the 12th fret, and hold it in place by pressing down on the string right behind it. Just like it's a fret. Now pluck the string. Does the harmonic thing go away? If it does, that indicates that it is a problem with the fingerboard surface. What you've done is raise the string up a little bit, while keeping everything else the same.

A high lump at the end of the fingerboard could explain why you are still getting the harmonics even after playing with relief, pickups, and changing strings.

Now there's something I hadn't tried yet. Very interesting suggestion. I'll try that later on today and post the results here.

Thanks!

 

[Mickets]

From the symptoms I'm reading, I think you may have a small high spot down at the end of the fingerboard. It's just touching the string enough to cause a harmonic to ring.

Here's a quick test: create a little false fret. Find a little piece of small bare metal wire. Bend it to a curve to match the fingerboard radius. Put it under the strings, maybe around the 12th fret, and hold it in place by pressing down on the string right behind it. Just like it's a fret. Now pluck the string. Does the harmonic thing go away? If it does, that indicates that it is a problem with the fingerboard surface. What you've done is raise the string up a little bit, while keeping everything else the same.

A high lump at the end of the fingerboard could explain why you are still getting the harmonics even after playing with relief, pickups, and changing strings.

OK, did the test. No change. But... I'm starting to thing the magnet pull on one of the pickups could be related.

 

[Mickets]

Ok so we have probably eliminated an electronic issue. I relistened to the video and noted something that may be relevant. Basically the same thing @Lofreck noted. With some notes it sounds like chorus. With other notes there are clear beat frequencies and the tempo of the beats seems to be related to neck position. This suggests the specific effect that manifests is related to string length.

For example you play a G harmonic (12th fret) and then fret the G at the 12th fret but slightly out of tune. The harmonic does not have chorus possibly because the string is vibrating in perfect harmony with itself, but you can hear the problem when you press the string down and the note is out of tune. At another time in the video, you play a note at the 12th fret and the chorus goes away as the note settles into pitch. Do you also hear the problem when you press the string down at the 12th fret and the note is perfectly in pitch? You may be getting sympathetic vibrations from the other strings you are not playing.

I see you have already addressed muting the string between the fretted note and the nut. I use left and right hand techniques to ensure none of the unplayed strings ring. Lay your right thumb flat across the unplayed lower pitched strings. Use your third or fourth finger to fret notes at the 12th fret and use one of your other fingers to mute all of the strings below the fretted note. Do you still have the problem? If the problem is still apparent with full muting I don't know what else to suggest.

I believe the usual suspects have been explored already: old/worn strings, twisted strings, pickup height, or issues between string height and neck relief/contour. Were your old strings the same brand and model? Did you set the witness points at the nut and bridge?

The old strings were already on the bass when I bought it, second hand. I suspect they were D'Addario, but I can't be sure. The new ones are GHS Bass Boomers.

Regarding witness points, this is the first time I hear of the term, but some research in the forums show me that I already did that without knowing there was a name to it. However, I didn't do it much on the bridge side. I'll try that next.

I think there could be something with the magents on one of the pickups...

 

[Mickets]

I had a very similar problem...on a Fender Stratocaster. It sounded just like your video. Turned out to be pickup height. I lowered the pickups, and the problem was solved.

So, pickup heights: I had already rulled that out, because:

1. The effect can be heard with the ear close to the neck, without the bass being plugged in.
2. I had already fiddled around with string heigts

But...

Well, I did a test today: I raised the pickup close to the neck to as high as it would go. And the effect got extremely worse! So even though I can hear the issue without the bass plugged in, I think maybe the magnet pull on the strings could be interfering with their vibration. More on some strings (higher magnets) than on others. Noticeably, the magnets under the A string are a bit higher for some reason, and that's where the issue is worse.

So I lowered the pickups as much as I could, and the issue's level just goes back to where it was on the video I posted. That is, I can't lower the pickups more. So then I raised the A string, to move it away from the magnet. Only minor improvement.

Strange is that the issue was not there, and I never changed pickup heights...


Additionally, today I also checked on:

• String twist: minor twist on A string, but also on others. Fixed.
• Bridge: tigthened bridge on to body (screws could turn more).
• Gears: adjusted/tightened.

Unfortunately, none of the above made any difference whatsoever. THe only thing that changed the sound was the pickup height, but still didn't resolve the issue.

Anyhow, I'm going to have to take it to a Luthier to take a closer look.

I'll keep you posted here.

THanks to all,

Mickets

 

[Mickets]

Do you have a small C clamp? Temporarily attach it to the headstock to see if the additional mass changes things.

Interesting idea. I'll get one and give it a try.

Mickets

 

[pcake]

are you playing near a ceiling fan? someone else here had that problem, and it turned out the fan was moving the strings across the pickups.

 

[HeavyDuty]

Interesting idea. I'll get one and give it a try.

Mickets

I’m suggesting it as a diagnostic tool, not something you leave on permanently.

 

[Trouztrouz]

I had this same problem turn up on a fretless after I changed the strings to GHS pressurewounds, particularly on the E string. Raising the action fixed the issue for me, although it did not occur to me to try lowering the pickups. I'll have to check that out to see it I can get the action back down to where it was.

 

[Turnaround]

All indicators are that it's still an interaction between the pickups and the strings, as in magnetic interference. Help me out here - fret each string in turn at the last fret and measure space between the pickup magnets and the bottom of the string - for each string and for each pickup. Report back.

You will still hear the effect unplugged if it's being caused by magnetic pull on the strings from the magnets in the pickups. The sound clips sure sound to me like a magnetic pull problem.

 

[Bruce Johnson]

Well, if you think it's a magnetic pull problem, there's a simple test for that. Find a moderately powerful magnet. Pluck the string, and hold the magnet as close to the string as you can, without sticking to it. Try it in different locations and see if you can create or change the warbling sound. Try it both plugged and unplugged.

 

[Mickets]

are you playing near a ceiling fan? someone else here had that problem, and it turned out the fan was moving the strings across the pickups.

Wow, never heard of that. But no, no ceiling fan. No fan at all, actually.

 

[Mickets]

Well, if you think it's a magnetic pull problem, there's a simple test for that. Find a moderately powerful magnet. Pluck the string, and hold the magnet as close to the string as you can, without sticking to it. Try it in different locations and see if you can create or change the warbling sound. Try it both plugged and unplugged.

Excellent idea - those hard disk drive magnets I kept now have a reason to exist...