Nut compensation

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AKEric
Myrtle
Posts: 50
Joined: Fri Sep 28, 2018 1:29 pm

Nut compensation

Post by AKEric » Mon Aug 17, 2020 11:48 am

I'm finishing up my forth guitar, and second one using both nut and saddle compensation. I have run into the same issue with both of them, although the first one ended up sounding terrific. I'm using the books second best method "Compensation without most of the mathematics" - Design pg. 4-119 (the best method intimidated me a little too much).

I've made a "dummy" nut with a 3mm set-back creating a string end point at the zero fret position for the scale length (650mm). I'm also using a homemade "Intonater" (ala StewMac) so I can adjust each strings end point at the saddle. I know this is not exactly like the the books process because it's not a designated test rig, but it seems like a reasonable substitute.

I tune the open string, and adjust the "intonater" so the 12th fret plays in tune. This also aids in determining the saddle compensation.

The procedure then has you fret the 1st fret and measure how much the notes play sharp, apply some math to this and come up with the amount of nut compensation. This all sounds very reasonable, but my notes at the 1st fret are all within 0.2 cents of the proper note which would give me almost no nut compensation. I'm using a Peterson Strobo+Plus electronic tuner which I believe to be fairly accurate.

Any ideas on what I'm doing wrong and what direction to go in? For the first guitar I ended up using close to the books values on Build pg. 21-14, and like I said, it sounds good with accurate tuning up and down the fret board.

One other thing. The elephant in the room. In determining nut and saddle compensation, the books emphasize testing the same type of strings that will be used on the guitar because of differences in manufacturers. But, I cannot imagine the same type of strings will be used throughout the long life of the guitar. Just saying.

Thanks for any help,

Eric

asgilbert
Blackwood
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Location: Perth, WA

Re: Nut compensation

Post by asgilbert » Mon Aug 17, 2020 6:41 pm

Good question Eric, All I do is use the Stewmac calculated intonation at the saddle end and then file the saddle to fine tune if needed. I can see you go to a much higher level than I do... so i will be interested the response from some gurus!!

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Trevor Gore
Blackwood
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Re: Nut compensation

Post by Trevor Gore » Wed Aug 19, 2020 10:03 pm

AKEric wrote:
Mon Aug 17, 2020 11:48 am
Any ideas on what I'm doing wrong and what direction to go in?
You're not necessarily doing anything wrong. It's always worth understanding what the causes of intonation errors are and (if you have the 2nd edition of the book) this is explained quantitatively in Appendix V. One of the major causes of intonation error is precisely where and how you finger the string when you fret it. If you "theoretically" fret the string (e.g with a theoretical "knife edge" right on top of the fret) you don't need any nut compensation. Most of us in the real world don't have fingers that approximate to that, and we fret the string somewhere in the span between two frets, depressing the string between the frets as we do so, and so we need nut compensation. So if you are very light fingered, maybe you don't need nut compensation, or maybe your measurement set-up is imprecise or maybe you "push" the fretted string, dropping the tension, and avoid it playing sharp that way. Some players get so accustomed to doing this they totally forget that they're doing it.
AKEric wrote:
Mon Aug 17, 2020 11:48 am
One other thing. The elephant in the room. In determining nut and saddle compensation, the books emphasize testing the same type of strings that will be used on the guitar because of differences in manufacturers. But, I cannot imagine the same type of strings will be used throughout the long life of the guitar.
Well, you have a choice. You can use a standard set-up that is always wrong for every set of strings that you use or you can optimise for a particular set of strings and enjoy the harmonicity, knowing that if you change brand you will still be likely better off than with a standard set-up.

But anyway, changing nuts and saddles is just routine maintenance on all guitars, so a new nut and saddle when you change string type is hardly a deal-breaker.

AKEric
Myrtle
Posts: 50
Joined: Fri Sep 28, 2018 1:29 pm

Re: Nut compensation

Post by AKEric » Thu Aug 20, 2020 3:40 am

Thank you Trevor,

I'll go back to the drawing board and make sure all the parameters are set correctly: Relief, action, nut string height and try again. Re-reading Apdx V was helpful. I'm sold on the concept, my execution just needs to be better.

I was slated to join you at Robbie's class in July. I'm very sorry it had to be canceled.

Eric

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