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Intonation

Discussion in 'Hardware, Setup & Repair [BG]' started by Tennesseemick, Feb 18, 2013.

  1. Tennesseemick

    Tennesseemick

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    I have a 2010 Jack Casady semi-hollow. I am trying to adjust the intonation but seem to be getting nowhere. I can get each string itself as well as the 12th fret harmonic to match intonation but playing the 12th fretted note is registering a bit sharp. I checked on line and read that fretted instruments will have some problems getting all three (open, 12th fretted, and 12th harmonic) to match exactly.

    So, here are my two questions:
    1. Is this really common?
    and
    2. Is it better to have the open and 12th fretted match or open and 12th harmonic?

    Thanks!:confused:
  2. 96tbird

    96tbird Supporter Supporting Member

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    The open and harmonic are the same; they always match. (Well, ok the harmonic is always at 50% of the distance between the nut and saddle.) Go ahead and drop tune any string and you'll see. You need the fretted to match the open and/ or harmonic.

    Make sure the thick part of the string (the whip) is not sitting on the saddle. You may need to use a spacer on the string ball to make the ball sit farther back. You need to press the strings down in front of the saddle and nut so a clean bend is made. The string needs to be perfectly straight between the two points; no arc. Just search "witness" for more info.

    Btw edit: how's your relief and action? Could be too high and you are pulling the string sharp.
  3. dmusic148

    dmusic148

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    If sharp at fret 12, move the saddle rearward to lengthen the string, thus flattening it.
  4. Tennesseemick

    Tennesseemick

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    Thanks. I got to pondering while walking the dogs and started to think these same things. Of course I need the open and fretted 12to match. Otherwise the BOOOSH will be a D...SH.

    I got into this mess when I changed strings and the whole bridge piece fell off, screws fell out of place and...and.... I'm am the poster boy for the anti-mechanically inclined.

    I'll try one idea at a time. Much gratitude to you all.
  5. JTE

    JTE Supporting Member

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    Change one string at a time. That way parts don't fall off. Setting intonation is getting the fretted notes to sound in tune with open strings... Well it's really getting it to play equally out of tune everywhere.

    You have yo compare fretted notes. Octave harmonics are by definition exact octaves of the open string regardless of where the saddles are. Comparing the 12th fret harmonic to the open string is pointless.

    Compare the open string, either with the fundamental or at the octave harmonic to the FRETTED 12th fret. If the fretted note is sharp, the distance from the fret to the saddle is too short (the shorter the string, the higher the pitch). So move the saddle away from the nut. If the fretted note is flat compared to the reference you need shorten the 12th fret to saddle distance.

    John
  6. 96tbird

    96tbird Supporter Supporting Member

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    Since it fell apart, you need to check the saddles. There are three different heights of saddles on those Epi bridges.
  7. redname

    redname

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    make minor adjustments, this way it won't affect the open string's intonation and still get the 12th fret note in tune.

    tht's what i noticed when i adjusted two of my 24 frets, i cld get the open, 12th fret and 24th fret spot on
  8. maturanesa

    maturanesa

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    adjusting the intonation is about compensating the 12 fretted note... open string and harmonic is the same...
  9. Tennesseemick

    Tennesseemick

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    Only one saddle fell out so its place was easy to figure out. I've been adjusting it but getting nowhere. I'm going to take it to the shop. The owner is always gracious and helpful. He had set the intonation originally so he knows the instrument. I really don't want to ruin the instrument.

    Thanks again, y'all!
  10. Solarmist

    Solarmist 15 miles from Mt Rainier Supporting Member

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    1) Yes - to different degrees. When you depress the string - it stretches it a tad thus sharpening it. It's more noticable - the higher your action is set.

    Is your action set too high?

    2) Match the 12th fret harmonic with the 12th fret note pressing as lightly as possible & right over the top of the fret. If it's too sharp for you still - flatten it a little by moving the saddle back a hair ... it will never be absolutely perfect.
  11. Tennesseemick

    Tennesseemick

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    I think the action is off but maybe too low. The screws that raise or lower it were barely in; that's why the bridge fell off when I removed the old strings so I may have over compensated when I put it back together.
  12. Tennesseemick

    Tennesseemick

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    Thanks everyone. The action was too low. All is good.
  13. rockinrayduke

    rockinrayduke Supporting Member

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    Every Epi 3 point bridge I've had the saddles are numbered, 1 to 4.
  14. Tennesseemick

    Tennesseemick

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    It got worse before it got better. The bushings had lost their grab so the whole bridge was off kilter. It's now fixed.

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