Newbie with a ticklish problem on an Epiphone

[Richard Freeman]

Hi all,

 

Just signed up and looking for help - or at least some new ideas. I have an Epiphone PR300 dreadnought, not my favourite guitar, bought it by accident, but it's better quality than my beloved old Yamaha FG160. It's developed a clear octave harmonic when plucking the open first string, unless you pick right over the 12th fret. No similar effects playing the same E elsewhere on the neck. A local repair man (a guitar tech, not a luthier, I'll warrant) can find nothing wrong, no loose or cracked components, saddle, nut or tuner issues. Same effect through several changes of string.

 

My next plan is to swap first and second strings and see what we get. Then maybe turn the saddle round to see what happens. But someone out there may know the answer. Any ideas would be most welcome. So many thanks in advance.

[Richard Freeman]

Good question. The answer is a definitive yes. My wife hears it.

I've spent a while plucking at the second string fretting the E at fifth fret. Yes it does sometimes cause the annoying E octave ring - but not anything like as loud as the open first string. Damping the top string makes no difference.

I'm left with two "almost certainties": 1 - it's the open first string that's got the problem; 2 - it's the 330 Hz frequency that is the problem.

I've tried to identify where the sound comes from - nut or saddle. The answer is both. Something is resonating with that 330 Hz frequency and setting off the annoying octave ring.

Process of elimination is the way to go. I'll switch strings around and try a substitute saddle. Watch this space.

[Richard Freeman]

OK, I've put an old 0.011" string in place of second and wound it up to first string pitch. Exactly the same effect - a niggling vibration pitched at the octave. OK when you pick at 12th fret, but clearly audible when you pick over the soundhole.

I guess this eliminates any issue specific to the first string - saddle, nut or tuner. I need to check out the truss rod in case it's loose. Otherwise it must be a natural resonance in the guitar or some damage which the repair man missed.

I'm rapidly running out of ideas here. Is it possible to damp a guitar to change its resonant frequency? Or will I have to keep this thing in open G or DADGAD for ever?

[Paul Verticchio]

Hi Richard.

I first wish to state that what I'm about to say is in no way disrespectful or snobbish.

I've assigned the term "cheap guitar syndrome" to these types of issues. I'm seeing more & more crazy issues with mega-factory Asian guitars (even from historically reputable manufacturers) sold on e-Bay or from big box stores.

About 9 months ago, a blowout sale on veneered figured topped Ibanez acoustics from a big box store that claims to be "our friend" brought in 4 models of the same guitar to the shop I do repair work for. The problem? A "sitar drone" from the G string on all 4.

I tried several levels of adjustment and repair and finally did a full blown fret level, re-crown & polish and replaced the nut & saddle on the first guitar that came in. No luck. The ONLY reason I did that much was because the customer loved the looks of the instrument and was willing to spend what I considered a grossly inordinate amount of money given the price & especially the poor overall sound of the guitar. He ended up returning the guitar and took credit toward a better model.

The next 3 that came through the door were given basic minor adjustments (to save the customers some $$) again with no success. I recommended the customers take advantage of the 45 day return policy the seller is famous for.

To digress just a bit, I've heard for years that the big box stores regularly receive "marginally acceptable" instruments from the manufacturers. They're big enough to survive the few returns they get from "picky players" and put their bets on buyers that "just won't notice" problematic issues.

The dealer I do work for has more or less confirmed that rumor to be fact. As explained to me, the lifeline to the better instruments is the independent retailer's sales rep who can better "guide" the properly crafted instruments to the dealer.

Whenever we have an instrument in the shop with some bizarre issue, I've begun asking where they bought the guitar? 90% of the time it's either "on e-Bay" or "I mail ordered it from [pick your favorite: MF, SA, ZZ, 123, etc.].

Back to the subject....What you have is a unique resonance caused by the specific properties of the wood & construction of your particular guitar. Let's face it; it's a $100 guitar and guitars can only be manufactured so cheaply before issues like these become more & more common.

Reality check: You have good ears as evidenced by your ability to identify the problem. Treat them to a higher quality guitar AND make sure you audition it before you buy it to avoid any more issues like this.

Best of luck and enjoy the music (:

[Rob Mercure]

What Richard stated makes sense. As a lot of you know I come to intrument repair from electonics repair and so this reminds me of a parasitic oscillation caused by unwanted coupling between circuit components. The solutions have generally been to lower the overall gain of the circuit slightly as the decrease in couping may not be proportionate or to add a specific filter that would eliminate the parasitic by removing it from the signal stream or shorting it out.

The reason I note this is that while at present I don't have a specific idea (I've been caught up in electronics repairs for the past few months and really don't have my "instrument" hat on) a more experienced repairman might think of how to bridge over or dampen the part of the instrument that resonates most at 330 Hz. Perhaps if some sort of "plucker" - a person or a machine with rotating fingers - could continuosly energize the string with the body flat on the bench then finger presure on specif spots might not a resonance. An alternative might be using an electret mic element mounted in a block of material to maintain a specific distance that's slowly moved over the top as the string is energized - while feeding the mic to an oscilloscope would be my technique a regular amplifier might reveal peak location. If the mic were coupled to the amplifier's speaker closely enough to be almost to the point of feed back that could make it even simpler - just sweep the mic over the table with the string energized until you get a horrible howl at one, or more, specific spots. Somewhere in my dusty, musty, distant past I remember "someone" repairing a similar situation on a Samick of some sort by locating a resonate spot and injecting some glue into the plies - I don't even think the spot was clamped afterward as the idea was void filliing and not strengthening (but I don't see how a void would howl so some of the memory might be bad).

If this were just one intrument developing a repair technique might not be worth it but it seems that finding some standard diagnostic and repair techniques - especially if they were quick and inexpensive - would pay off especially to those who solely depend on repairs for make a living.

Rob

[Richard Freeman]

Hi Paul

I have no idea where this particular guitar was bought - I didn't intend to buy it myself but after two years on loan from its previous owner, it was easier to send a cheque than return the instrument. It certainly didn't have the irritating harmonic at that stage.

I'm not sure it is a $100 guitar, but even if it is it should be possible to mass-produce these things to a consistent standard. "Epiphone by Gibson" believe themselves to be a strong brand (yes it does say "Gibson" on the truss rod cover) - the only PR model in their current range retails at $182. If you couldn't get a usable guitar for that price, there would be precious few young players coming through. I have a range of "cheap" guitars (all Yamahas) which have been excellent, especially the FG160, Taiwan-made Black Label model from 1975, laminated construction and sweet as can be.

I don't believe I need a better guitar for my purposes - I have several instruments to choose from and not a great deal of time. But my keen engineering mind is telling me that there is a fix for this problem.

[Paul Verticchio]

Perhaps I should have called it an inexpensive guitar. It's made for the beginner and casual player. In other words, it's not what I would consider a professional quality instrument.

I'm not insulting your guitar, I'm just stating my observations based upon my experiences.

When my Yamaha FG180 no longer satisfied my sonic expectations, I got a Martin D-28 (in 1970). When it went terribly "wonky", I got a Taylor which still meets my expectations.

Finally, IMHO, the brand name "Gibson" no longer represents "the pinnacle of quality" or a good value based simply upon their woeful QC and exorbitant prices. It recently took me 3 hours of work to get a brand new $8K R9 LPS playable for the customer. (fret level & dress, intonation was abysmal, numerous finish flaws, etc.)...well, something is wrong with that picture. Oh ya, and this guitar had the legendary Plek treatment. I guess no one was watching the machine while it did (didn't do) its job. Gibson is better at marketing its brand name than it is at actually making guitars.

May I make a suggestion: next time you have an issue, please do everything you can to try & eliminate the issue before you post. "Once I've eliminated loose truss rod or tuner components as possible causes, I'll have to try to shift that resonant frequency." All of these items should have been tried before you posted as it helps to keep the solution guessing to minimum. Guitar repair is a very precise art.

Best of luck (:

[Ned Knepp]

Paul,
I am not a pro at guitar repair but I have a lot of trouble shooting experience in other fields. Sometimes it helps a lot to "talk" it over with someone else, or in this case post questions/comments on a forum. Some of the process may appear obvious to you but not be so clear to others. What you would have done before you posted is based on your thought processes and your experience. Not everyone is going to have your experience or follow your processes.

Personally, I don't mind reading thoughtful posts from people that may not have tried everything else first. The process of trouble shooting is different for each problem and each troubleshooter. I do not think that it is necessary to have tried everything before posting in a forum. Besides, I think there has been enough discussion about minimizing repairs to keep them affordable to indicate that it is possible to make a guitar functional, but not precisely perfect.

Ned

[Arthur Sweeney]

Am I to believe then that my Martin DXM is a "cheap" guitar, because it has this issue also?

[Paul Verticchio]

In the context of quality components; yes. Although I consider Formica guitars more as a short step above toy guitars.

[Howard Klepper]

I must be missing something. Doesn't one always get an octave harmonic?

[Pierre-Antoine Roiron]

Yes you always have one, you can even train your ear to hear others. I believe the issue here is that this specific harmonic is too loud.
I think Paul and Rob pretty well made the point.

Richard, now you'll have to live with it or innovate. Maybe you could try to glue (or double tape) a heavy block of wood or anything else somewhere on the top and see if it can shift the 330Hz resonant peak to a frequency where it won't be that annoying. Of maybe try to put a plastic bottle or a box inside the guitar to change its volume and its resonant frequencies.... Be creative! Good luck.

[Richard Freeman]

Many thanks to Rob and Pierre-Antoine for these ideas. Once I've eliminated loose truss rod or tuner components as possible causes, I'll have to try to shift that resonant frequency. Early stages of my research indicate that 330 Hz is possibly too high to be the back, top or body resonance - more likely the two halves of the top interacting with each other (Hey, don't believe everything you read on the internet!).

I will be trying all the ideas above and more. Or maybe just tuning it to open G and getting on with my life.