buzz from a resonator cone... what to do?

[Christina Perry]

Hi, all -

I have a National ukulele that is a few years old and in great shape overall. But I've noticed a small buzz coming from the biscuit/cone area on the C string (not on all C's, just the open C string). It happens most of the time when the C is plucked (especially near where the neck meets the body), and the buzz definitely seems to be coming from the biscuit area, but could be anywhere in the cone. It also can be heard when strumming chords that include an open C.

Could you please provide some guidance as to what things I should look for, and where to begin? I'm comfortable opening it up to troubleshoot if necessary, with some guidance, but I'm unfamiliar with resonators, so I don't want to do too much until I know what I'm looking for and if there's anything in particular I should be careful NOT to do! I appreciate any thoughts on how to proceed... and of course, if it's so delicate or fiddly that I should just leave it to an experienced tech, that's okay too!

Thanks very much,

Christina

[Robbie Collins]

Hi Christina,

I haven't played a resonator uke but it sounds intriguing.  I'm now refretting my Cordoba uke after inlaying a gold MOP "C" in the headstock and dots in the fingerboard. Guitar dot spacing for me!

As for your buzz, (1) check to see if the cone is firmly seating and not sitting on a wood chip, glue or lacquer run, etc. and (2) check to see that the biscuit is seating flat upon the resonator cone.

Here is a good photo-essay on setting up a resonator and fixing common problems:

http://www.stewmac.com/freeinfo/String_action_and_setup/i-4006.html

Hope this helps,

Robbie Collins

[Ned Knepp]

Hi Christina,

 I don't know much about resonator's and there are others that visit this site that do but I think before I started taking things apart, I would try slipping a small piece of paper between the C string and the back edge of the bridge just to see if it makes any difference in the buzz. Definitely NOT a fix but it might help determine where the buzz is located. If it's the string on the bridge this simple test may tell you without taking things apart.  You might want to check the nut slot too just to make sure. 

What happens if you tune the C higher or lower? Still buzzing?

[Robbie Collins]

Does it buzz if you fret a C#? If not, that would take the nut out of the equation.

Personally, I tend to reserve the term "buzz" for strings rattling against frets to distinguish that source of noise from resonances. A resonance would be, in this case, something vibrating sympathetically to the fundamental or harmonics of the Open C.  Some resonances can't be removed, just mitigated.

A great technique I learned rebuilding my '59 Volvo is to use a piece of flexible tubing as a stethoscope.  Stick one end of the tubing in an ear, have a friend pluck the string, and move the other end around the guitar. Don't actually touch the end to the guitar or you may dampen the vibration.

I wouldn't be too worried about disassembling the thing. It's not rocket science. Just take pictures with your phone at each stage, put all smaller parts in a Pyrex tor Tupperware container, and take notes if necessary.  Don't worry about the nerd factor, I've found that technical knowledge of my instrument has helped both my playing and my evaluation of potential purchases.

[Hesh Breakstone]

Ever hear the tune "One Toke Over The Line?"  Resonators are often very close to one buzz/rattle/extranious, unwanted noise over the line.  By their nature and how they are susposed to work there is a lot of room for things to rattle and buzz.

What Robbie said is most of what you want to do and that is take it apart, perhaps photograph the various stages of disassembly with your phone to help you sort it out later when you reassemble it.  What you are looking for is decent contact on the mating parts.  Sometimes we can help the fit with a little encouragement and other times simply rotating things from the status quo can provide better fitting parts.  

I've not had the pleasure of taking one of these ukes apart yet but likely will since ukes are so very popular these days. But regardless of if it's a uke or guitar styled resonator the principals are the same, endeavor to have uniform fit and contact all aroound the cone and other parts and upon restring the buzz may be gone.  Mind you you may have introduced a new and different buzz or rattle but sometimes we do the best we can and then resort to trial and error.

[Robbie Collins]

Word.

[Christina Perry]

All excellent suggestions, thank you so much!

I will take it apart this weekend and follow all of the above steps, including photos (I do that a lot when I take appliances apart to fix them). I'll report back on how it goes and the results...

thanks again, I truly appreciate the help!

Christina

[Jon Hiltbrand]

The first place I would check for buzzing on any resonator guitar is the coverplate. If the coverplate is not firmly seated on the top it will buzz like crazy.  Some coverplates are held on with machine screws but most are just small wood screws. Many times these holes will need to be filled and re-drilled in order to get enough bite to pull the cover down securely.  If putting a bit of pressure on the coverplate in different spots stops the buzz then you have your answer.

Next best thing is to take it apart and inspect the conewell surface as suggested above.

Did the buzz just start or has it always been this way?

[Greg Mirken]

Stop; before you start taking it apart, you say that the only note that buzzes is the open C string. No harm in checking the coverplate screws, but if the 1st fret C# doesn't buzz, and a fretted C note elsewhere on the fretboard doesn't buzz, the only possible cause of that buzz is at the nut. Either the slot is too low, allowing the string to zing against the 1st fret, or the slot is angled poorly causing the string to zing within the slot itself.

I know it sounds like the buzz is somewhere in the cone, but that's just because it's the cone's job to amplify sounds.

I worked for Dobro doing assembly, setups and repairs in the 70s and I have done work for National Resophonic for many years too. Opening it up is likely to cause more buzzes than you started with if you're not used to working on these beasts.

[Christina Perry]

Thanks Greg, great points! I will be looking into this much deeper this weekend, and I will start by looking at what you suggest. Definitely don't want to take this thing apart if I don't have to. I'll confirm that it's only open C (I think it is, but I'll make a more focused study), and proceed from there...

thanks again to all!

c

[Ron frazier]

I build dobro type guitars   Robro Guitars. is my name. I would have to guess at what is wrong with your insterment. My first check is like Greg says is play it when it is tuned to pitch then fret it at the first fret and if it leaves it is in the nut and correct it like Greg says if it is still there it is at the cone. Tap around the cone and see if you can get a rattle.  If not try pushing down on the bridge and see if it leaves , The ledge could be loose from the cone or the cone is not seated to the guitar top.  If that is the case I would cut a circle the size of the cone and glue sandpaper to one side then with a pencel mark the ledge and spin the sandpaper around until you remove the marks.

Have fun

Robroron    PS  Greg  Do you remember a Jim Bradly that visited with you guys back then.  He is a friend of mine.

[Greg Miller]

I acquired a steel single cone biscuit bridge resonator awhile back that is in need of some restoration. 

What I'd really like to find is a good book on resonator guitar maintenance and setup.  Suggestions welcome.

I have snippets of info from Stewmac, National, and Beard guitars.  Besides a thorough cleaning this project will be replacing the nut, cone, and biscuit/saddle.  I intend to set it up for fretted play versus slide with an action at about 4/64 low and 3/64 high at 12th fret depending how the guitar responds.  I've opted to try Nationals new Revolution biscuit/saddle (aluminum biscuit with wood compensated saddle (varying species)) with their Hot Rod cone.  Besides the procedures common to an acoustic, I have some questions regarding the resonator end of the business:

1.  Gluing the biscuit to the cone.  I get the impression that the purpose is really as an anti-rattle preventative since there is a screw mechanically fitting the parts.  Some folks are in the no glue camp.  Many use wood glue which doesn't make sense to me.  If it is necessary, then I think more down the lines of a thin bead of rubber cement or a three to four pin head drops of gel superglue like one would use installing a nut.  Also being the Revolution biscuit uses a machine screw versus wood screw a dab of thread lock could be prudent.  In any case, since the cone sweet spot has to be found/maintained, and the biscuit/saddle orientation for intonation purposes has to be performed, if glue is needed I really lean more to an adhesive that allows non-destructible parts separation and adjustment. Thoughts?

2.  Method of determining proper break angle between saddle and tail piece.  National has told me that it was a secret.  Beard says about 5 to 7 degrees.  However there must be a method behind it.  Inputs?  

[Greg Mirken]

1. No glue; no threadlock. When I was at Dobro we used AR glue between the biscuit and cone,which always seemed stupid to me because it invariably lets go of the aluminum and can start a rattle. Anything squishy in there seems like a bad idea.

2. The angle across the saddle is trivial. It's not the downward force that drives the cone. 5 to 7 degrees is fine.

Photos would be good. What make is the guitar?