12 string intonation help, please...

Setup, repair and restoration of Rickenbacker Instruments

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kiss-my-axe
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12 string intonation help, please...

Post by kiss-my-axe »

Hello,

I've personally been setting up my 4 RIC's ( 2x12 strings, 6 string & bass ) for years now with good success and without any particular issues, but I've now run into an issue with one of my 12 strings that I want to be cautious about how to fix. Hoping there's someone here that can properly advise.

I'm using Pyramid Chrome Flats - 010-046.5 with a 6 saddle 12 string bridge as I have been using for years. Recently changed the strings after an extended period of non-use, checked all of my setup measurements and intonation. All seems well. But after a short period of playing, I've noticed that the octave 'A' string has a pronounced 'sitar' buzz. This occurs only when fretting the A string course starting at the 2nd fret and going up the neck gradually disappearing by the 7th fret AND it's ONLY the octave A string buzzing - no other 'sitar' buzzing on any other courses or even the entire low A string.

The guitar is setup atm with a nearly flat neck - only a very slight relief. Action otherwise is pretty low. I used a fret level checker thinking maybe I had a high or low fret some where in the area, but found nothing. After more analyzing, the buzzing seems to be localized at the bridge rather than buzzing against the fretboard. The frets overall on this guitar are in excellent condition. In this case, I would normally think that a little massaging of the octave bridge slot would remedy. With this in mind, I did very carefully attempt to cleanup and profile the octave A string bridge saddle with a nut file, but that didn't seem to reduce the buzz much if at all. Of course, this may require more aggressive profiling if indeed the 'fix', but it's here where I want to make sure I'm working at this properly.

I suppose it's also possible I have a bad A octave string, but unfortunately as far as I'm aware, one cannot buy Pyramid flat wound singles. I guess I could try another string mfg'r flat wound assuming there are alternative options out there, but spending $40 or so on another set of Pyramid strings just to 'test' a string seems punitive.

One last thing that seem strange... When the A string course is perfectly in tune with each other - open fret, fretting the A string course gets more and more out of tune ( to each other ) as I fret up the guitar. At the 12th fret the A octave string is 22 cents out of tune sharp. So, open fret, both A strings are perfect 0.00 440A. At the 12th fret, the low octave is 0.0, but the octave A is +22 cents. Yes, I undertand that using a 6 saddle bridge will not allow perfect intonation. Teh other 5 courses do not exhibit this issue. They are reasonably close to being 'perfect' intonated.

Open to suggestions! Thanks in advance!

~ Greg
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jdogric12
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Re: 12 string intonation help, please...

Post by jdogric12 »

First the string buzz:
I would take off the string, save it, and try another - any string of the same gauge just to see what happens. It really sounds like a burr in that saddle - like you checked, so that's weird, or may jsut need a second pair of (tech) eyes.

Second, the intonation issue... that's a Rick 12 with a 6-saddle for you, although you're right that is a little extreme. I wonder if you jsut got a funky string or something. Ever tried TI Flats?
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Ratwax
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Re: 12 string intonation help, please...

Post by Ratwax »

Hi Greg,

The spring tensioning the saddle in the bridge may be rattling, too. When checking the buzz see if you can squeeze a tipex, or something small, against the spring to absorb any vibration. If it has super compressed over time it mightn't be doing it's job, or even be broken. That could also account for both effects.

Cheers,
Andrew

1989 620/12,
2003 4003
1986 330
1991 381 V69
1998 650 Dakota
Plus various Squiers and stuff
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iiipopes
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Re: 12 string intonation help, please...

Post by iiipopes »

Pyramids are bad strings to use on a Rickenbacker 12-string, because of their core/wrap ratios cause the problems you are encountering as well as tension issues. The reason the A string, and probably the low E string as well, don't intonate going up the neck is because the different diameter cores need different compensation at the bridge, and won't intonate together. It's the same as with those 12-string sets that have a plain G unison string rather than a wound. The same issue occurs with those sets on the pair of G strings.

Short-term solution: cut a small piece of the A string leader, unwrap it, and measure the diameter of the core. Get a plain string one size larger than the core diameter of the low a string. That will help the intonation.

The other issue, the buzz, may be caused by the unison A string being a larger diameter than the stock set of strings or the other sets that are commonly used. This will cause the unison A string to set up higher in the bridge saddle and possibly the nut slot. When the bridge is lowered to get really low action, this will lower the octave A string, which is probably sitting in the bottom of the slots, to get too low and buzz. The only solution is to either use a smaller diameter unison string and raise the bridge, or have a new saddle cut.

I did the saddle cut. The low E string pair are also prone to intonation difficulties, so I cut a custom E string saddle so the unison string intonates off the back of the saddle, and the octave wound low E string intonates off the front of the saddle to fix the intonation issues.
12-StringBridgeCloseUpSmallVersion.jpg
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