Mystery Buzz

[Scott Syltebo (bonesrad)]

Hi there,
 
I'm experiencing a mystery buzz that has me a bit puzzled on my Series II.  What's odd is it seems to be isolated to one string at a time, yet each string has had the buzz occur from time to time (most often it occurs on the A and D strings).  The buzz is metalic in nature but isn't a fret buzz.  I've checked all of the screws on the bass and they are tightly secured.  I think the culprit might be the bridge as when I raise nad lower the height of it, the buzz tends to move to a different string.  Additionally, I've when I pluck nearer the neck, the buzz sometimes goes away.
 
If anybody has experienced something similar, I'd love your input.
 
Thanks,
Scott

[Kent Fossgreen (xlrogue6)]

Make sure you check the intonation screws--without string tension on the saddle the intonation screw should be just beyond finger tight--too loose and the screw head and the nut can rattle, too tight and you risk bending the bridge rail, not to mention making intonation adjustment VERY difficult.
 
Also check the screws on the ends of the bridge that attach the rails to the spacers and the screw or screws that secure your sustain block, if your instrument's got one.

[Kent Fossgreen (xlrogue6)]

Oh yeah, don't forget to check the tightness of the height adjustment screw nuts on the underside of the bridge.  With no strings on the bass see if the bridge rocks front-to-back.  If it does, tighten the nuts enough to eliminate as much of the rocking as possible while leaving the bolt loose enough to adjust without stripping the head.

[Scott Syltebo (bonesrad)]

Kent,
 
Thanks for your words of advice.  Just a couple weeks ago, I removed the strings, checked the bridge rock and noticed that it did move significantly.  When you mention adjusting the screw nut, are referencing those right under the bridge, or those under the plate that the bridge screws into.  If the latter, I would assume that you would have to remove the plate to make the adjustment.
 
Thanks again,
Scott  

[Mark DuFresne (markus)]

Scott,
 
All good ideas from Kent. Probably worth checking this stuff periodically even if there is no noise.
 
That plate that the bridge screws into is actually a big block of brass and there's nothing much under it but the hole it fits into.  
 
I had a buzz problem on my five string similar to yours. Mine was on the A string. It turned out to be wear at the nut -- or lighter guage strings than those originally used by the Alembic masters. (Probably not so uncommon for those of us with five strings because there is a set screw under the A string and that doesn't leave a whole lot of brass holding the string up). I could make the buzz stop by plucking the open string and pressing my fingernail down on the string on the body side of the nut. A little file action fixed it for now but that's something that you might want to leave to an experienced luthier.
 
A good way to tell if your problem is at the nut: do you hear the buzz on ONLY open strings?  
 
Mark

[Scott Syltebo (bonesrad)]

Mark,
 
Thanks for the response.  I have to say this message board is really a great resourse for all things Alembic.
 
Actually, I tend to hear the buzz more often when the string is depressed on the fretboard.  I have noticed the buzz is temporarily relieved by repositioning the string close to the bridge.  I'll try some adjusting when I get home tonight.  I definitely wont get drastic with it, though.  If the bass needs major tinkering, I think I'll send it back to it's birthplace.
 
Scott

[Nate Pitts (cntrabssn)]

Scott,
 
Also, try following Mark's suggestion, but check between the bridge and the tailpiece. It might be worth checking since you mentioned that changing the bridge height changes the buzz. If the problem's between the bridge and tailpiece, I think you would notice it on open and fretted strings.  
 
- nate.

[Kent Fossgreen (xlrogue6)]

Another potential source of buzz is string to bridge rail contact.  This can happen on the tailpiece side on some instruments although generally you have to raise the action to profoundly non-Alembic heights to make this happen.  It can also occur on the pickup side if you're using a taperwound string on a saddle that's cut for non-tapers (assuming you've found a taperwound with a long enough taper to even fit an Alembic!).
 
And yes, there are no nuts under the sustain block--I was referring to the ones on the bottom side of the bridge.  Sorry my original post didn't make this clear.

[Adriaan Simons (adriaan)]

Same problem, different bass - my Epic has a mystery buzz as well that you can't hear through to the amplifier. My latest theory is that it could be the ferrite ring in the electronics cavity rattling against the cover or the electronic components. The wiring is led though this ring to prevent hum, I guess.
 
The ferrite ring has a small piece of foam attached to one side to prevent such a buzz, so I'll try additional pieces of foam to see if that stops the buzz.

[Kent Fossgreen (xlrogue6)]

Well, now that you mention it...
The ferrite beads can indeed cause rattle if they contact the cover plate--judicious application of foam in the cavity will alleviate this.