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Portland Guitar Co. | Portland Oregon | Contact Jay Dickinson-503.245.3276 | jay@portlandguitar.com

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Portland Guitar Pretty Good Intonation (PGPG) System

Short Version | Introduction | Intonation Errors | Analysis | PG Approach | Comparisons | Conclusion

PGPG Intonation


          The quality of an acoustic instrument has many elements with the sound it makes one of the most important.  Intonation or how well it is in tune is a major component of sound quality.  Needless to say, a well-tuned guitar sounds better than one out of tune. To enable our efforts I have develop a set of technologies and a system that is compatible with an acoustic guitar.  The Portland Guitar Pretty Good (PGPG) Intonation System works Pretty Good, not perfectly, but pretty good.  The basic physics and mathematics of the system is well known and has been for a very long time.  This new system is flexible and adaptable and can be changed as the guitar matures and changes.  The system should be applicable to other stringed instruments.  The real opportunity here is crafting a new class of instruments that raise the level of quality by several factors, but a rearguard action can be taken to retrofit instruments already made. 

Although not trivial to manufacture, the components for the system are straightforward, simple and intuitive.  If getting to perfection is an admirable but fool’s errand it comes at the price of manufacture complexity, setup and maintenance, or else simplicity.  The PGPG Intonation system works well for this purpose.  It is easy to build if you have the right tools, is mostly intuitive, addresses intonation in-situ and respects the guitargeist of the instrument.  But, it is much more complex than a straight line bone saddle and nut which works well enough for the majority of instruments.  Using this system should help when the errors of the standard systems are not acceptable.  If it has to be as right as possible however, this may be a way to get there. When the setup and maintenance steps are an acceptable burden then the results of this system may well be worthwhile.  On the other hand, perhaps it is time we finally hear our guitars in tune.  Even given the increased complexity of the PGPG system, so far it seems to be stable and robust and easy to implement.  Only patience will tell if it will stand the test of time… or is that the test of tune… we shall see.  My hope is that this system helps us enhance and enjoy the beautiful sounds these wonderful instruments make.



An Amusing Antidote

            When I was developing this technique I had finally put everything together and tuned up my new guitar.  I then started to apply the PGPG intonation process and watched the graphs converge on the zero line.  I kept working at it and started to get frustrated with the variation.  I poked and prodded and re-measured every note a dozen times.  I finally gave up and said that this is as good I can do I guess.  I thought to myself that this works, but only to a degree.  Then a brilliant idea, let’s check another guitar.  So I grabbed my Collings D2H since if I had to face the music as, it were, this was the guitar to compare.  I started to go through the process and got the first results.  I finished up and looked at the graph and compared it to my new guitar and then went back and forth.  Hmmm, maybe I’m on to something here.  I promptly stopped working on my guitar and celebrated… Hazzah!


What’s Next, Follow-On Research and Development

Make measurements easier: One has to admit that measuring every note on the guitar several times is a tedious, boring time consuming process.  It would be desirable to find a proxy for a full set of measurements, that is, what is the minimum number of measurements that need to be taken to get the same results as when a full set of measurements is used.

Reduce measurement error: Presently measurement error seems to be the limiting factor to improving the results.  If we can increase the signal to noise level of the intonation measurements we should reveal the individual errors that the frets are introducing, and perhaps the resonance interaction will become more apparent.  The fact that the notes pitch follows a trajectory that takes it from sharp to flat to sharp to whatever as it loses energy is a particular problem.  To improve accuracy there are at least two paths to follow.  One is to use a spectrograph to record the data.  This increases the complexity of the measurement and can increase the time required for each measurement depending on precision.  The results from a spectrograph are high quality and the method is worth pursuing although cost is prohibitive.  The second path to pursue is to develop a transducer that can be lightly coupled to the strings.  By using a high precision audio generator we can fret each note on the fretboard and then tune the generator to excite the fundamental of the string.  This method has the advantage that the measurement is made at a steady state condition and should eliminate frequency wander.  The disadvantage is that the coupling between the transducer and the string may alter the resonance slightly.  This would need to be investigated.

A lot can be learned about the intonation characteristics of guitars by conducting a survey of instruments.  What we don’t know is what we don’t know and it would be nice to shed some light on the subject.  I would like to measure as many guitars I can get access to.  It will be important to examine the gamut of instruments form off the shelf to custom high performance guitars so that we can see what works and what doesn’t.

Continue to develop the adjustable nuts into more elegant a sophisticated designs.

Spread the word about this new development.

And finally and most important, build more guitars.