Mysterious buzz repair

I don’t take on many repair jobs, but this one came in from one of Craig’s students, and I couldn’t say no. It is a beautiful, simple guitar made by a Swedish guitar builder, Bo Wretling in 1968. The guitar is really easy to play due to a 630mm scale length, low action, and a narrow and thin neck. The trouble was that it had an annoying buzz on the low open strings, and sometimes in the 1st and 2nd fret positions.

Of course, my immediate thought was that it would be a simple action or fret issue – the action at the first fret was quite a bit lower than I would normally have a guitar set up. Normally I set the first fret action on the 6th string to about 1mm so that I can really dig in when I am playing and not worry about buzzing. This guitar was just about 0.5mm at the 1st fret, 6th string, which is very low for a classical guitar.

With this in mind, I started by trying to raise the action at the nut, adding shims and hoping to get rid of the buzz. Nothing worked – even when the action was well over 1.5mm, the buzz rang out, maybe even worse than before.

So I removed the strings and reached inside the guitar, thinking that I might find a loose brace. And I did – there was a pad just under the bridge that was not glued down very well, so I thought “awesome, I’ve solved it. Simple fix.” I boiled up some glue and worked it into the crack, which took some doing – it is not easy to get glue into a place that you can’t see. It took two sessions of gluing to get the pad secured. I let it sit for a day and then restrung the guitar only to find that my repair had done absolutely nothing for the buzz.

Next I checked the tuning machines – they seemed to rattle a bit when tapped, and the buzz did sound faintly metallic, so perhaps it was just a sympathetic buzz from old tuning machines. But even when I removed the offending tuner, the guitar continued to buzz.

Fed up, perplexed, and frustrated, I decided to get some felt and mute all of the possible rattles from strings and tuning machines just to make sure that it wasn’t just a loose string end buzzing against a piece of wood or a back buzz from one of the strings where it touched the headstock. It wasn’t any of these things – the buzz continued.

Then I decided to take a closer look at the bridge, and noticed that the string holes in the tie block were extremely worn. I also noticed that when I touched the 6th string behind the saddle, the buzz stopped. At this point I was pretty sure that the buzz was coming from the saddle, so I just had to figure out how to stop it. I decided to try an absurdly high saddle to see if that would stop the buzz, and it did. Finally there was no buzz. Of course, it also made the guitar completely unplayable, but at least I knew what the problem was.

Because of how worn the tie-block holes were, there was almost no break angle over the saddle, so the bass strings were flapping against the saddle. This explained why the buzzes only happened with open strings or in the lower positions – playing a note a the 12th fret or in a higher position would put enough force down on the saddle to prevent the buzz, but there was not enough downward pressure with open strings or in the first and second frets.

All I had to do was figure out how to repair the holes and/or change the string-break angle. Luckily I was spending 24 hours by myself in a car last weekend (13 hours to and 11 hours back from Virginia for my concert in Charlottesville), so I had plenty of time to come up with ideas.

Solution number 1 would be to use a higher saddle. The trouble with that is that the action at the 12th fret was already about 4.5mm, which is about the highest that I would like it to be for playability. A higher saddle could also compromise the intonation of the instrument, so I decided against this.

Solution number 2 would be to somehow make tiny wedges to attach inside the worn tie block holes. I ruled this one out because it seemed way too finicky and liable to fail in the next couple of months or when the strings get changed.

Solution number 3 would be to remove the bridge and either make a new bridge or repair the existing one. I decided that this would potentially cause a lot of damage to the instrument, and would be very labour intensive, so I decided not to remove the bridge.

The final solution that I came up with was to just replace the tie block itself. This was by far the simplest, least invasive and most likely to last solution that I could come up with, so I got to work by cutting off the tie-block with my Japanese saw. I then cleaned up the cut with a small plane, chisel, and some sandpaper so that the tie block area was left perfectly flat and ready for a new block.

I used the saw to cut off the tie block because I wanted to save the mosaic inlay that was atop the block so that I could attach it to the new block to make the repair less noticeable.

I made a new block out of ebony – the original bridge is rosewood, but I decided to use ebony so that the holes don’t wear as badly. Once I had the block sized and drilled, I glued the original mosaic veneer to the top

and then glued the tie block to the bridge.

I fashioned a makeshift caul for the inside of the guitar out of cork and a scrap piece of wood, and clamped the tie block much like I would a bridge.

After a little bit of clean up and a quick coat of shellac, I think it looks pretty great:

The repair is not invisible – if you look closely, you can see that the tie block is now a sandwich of rosewood and ebony, but it is not noticeable at first glance.

Of course, the best part is that this repair worked. By increasing the string-break angle by a little bit (I should have measured the before and after), I managed to eliminate the buzz, and improve the tone of this guitar. This was a good exercise for me actually as it proved the importance of a good string-break angle in guitar construction. (This was not the fault of the original builder, just the wearing of time). I will be more aware of this in my own construction from this point on.

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Emily

I play guitar. I build guitars when I can. I enjoy all sorts of music, but Baroque, 'classical' guitar music of the 19th and 20th centuries, and jazz music hold special places in my heart. I am using this blog to document some of my adventures in guitar building, performing, and teaching, and hope to give my readers a bit of a look at the world inside a guitar.

6 thoughts on “Mysterious buzz repair”

  1. Awesome repair work! Now I wonder whether you were “properly” compensated for such time and effort, or it was meant as a partial gift to that student? 😉

  2. Very nice Emily
    I appreciate the trouble shooting you performed in getting to the problems and in how you solved it. This kind of dedication is what makes a luthier rise to the top. The constant search for
    “ improvement “ shows in your instruments.
    Enjoyed the read very much.
    Regards
    Robt

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