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A "parasite" tone

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Re: A "parasite" tone

Postby Massimo Milan » Tue Aug 30, 2016 10:48 am

Bob Gramann wrote:I used closeup lens on a DSLR camera and made a movie of the string at the fret. It showed clearly that the string jumped off the fret after the initial pluck. I couldn't record at any more than the standard 30 fps, so I couldn't do a good slow motion video. But, I would assume that if there is enough energy at the initial pluck to lift the string obviously off the fret, there is probably enough to lift it on subsequent vibrations. I'm going with the jumping string theory.

On a steel string gutar, you don't get good tone if you depress too far back from the fret. I guess that's why this isn't an issue on the nylon string guitar when I play--I'm used to fretting right behind the fret.


One of the things i noticed is that the abnormal tone generates even plucking gently. Anyway, I'm asking which can be the physical difference between nylon and steel strings which makes the nylon string to jump off the fret and the steel one not. Tension? So High tension would help, but different nylon string sets did not show any difference. Mass? it is assumed that steel and brass have more mass than nylon. So what else? What could help, even assuming a defective playing technique, to minimize the "jumping off phenomenon"?
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Re: A "parasite" tone

Postby Massimo Milan » Tue Aug 30, 2016 10:51 am

Well (gosh!!) , this is what today says the guy who wrote a post back in 2013 in another forum:
"All you folks giving the op grief about it being his technique need to zip it. It is absolutely not his technique. It is NOT the kind of buzz you get if you are in the middle of the fret and not pushing hard enough. No, this is an unholy demon level buzz. I'm the one who started the other thread about this problem three years ago. Understand that this is not just your normal buzzing. It is almost as if a secondary note comes through. The Paul Mcgill article is a perfect illustration of the problem. As the article states, if you move even 1/8 of an inch from the fret this problem can appear. There is no way in all hell that every single finger on every single chord can be played 1/8 of an inch or less from the fret. The op does not sound like a noob when it comes to guitar, I'm not either. I teach guitar all day every day, have taught almost 40,000 lessons, do repairs and setups on the side, etc., this problem is as strange as they come. What Mcgill says is correct. The note j
ust "accelerates" off the fret, almost as if it is oscillating too rapidly or something. I was driven mad by this problem on a Cervantes Crossover. Had it worked on by the best repair guys around. Never got solved and ended up sending the guitar back after many weeks of trying everything we could think of. Bought a Kenny Hill and no issues.

It was literally the most frustrating problem I've ever had on a guitar in my 25 years of playing. I have owned dozens of guitars, but none had such a problem as this Cervantes. I've had back buzz problems, fret buzz, etc., and I always was able to fix those issues, but the demon buzz defeated me and was never solved. **** shame too because the Cervantes felt great."

Isn't it enough?
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Re: A "parasite" tone

Postby Eric Baack » Tue Aug 30, 2016 11:07 am

Oh for a high speed video camera....
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Re: A "parasite" tone

Postby Eric Knapp » Tue Aug 30, 2016 1:36 pm

Eric Baack wrote:Oh for a high speed video camera....

A lot of current smart phones can do slow motion video. For example, my iPhone did this.

https://youtu.be/prwutuwkBSs

That's a 2-year-old model. The current one can be twice as good. If you know someone with one you could capture something that would work.

-Eric
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Re: A "parasite" tone

Postby Bob Gramann » Tue Aug 30, 2016 2:22 pm

Eric's suggestion of the phone works. My wife's iPhone 6 records in slow motion. When recording from the side, it shows an initial jump at the fret. When looking down at the string, it shows the string vibrating side to side all the way back to the finger like Al Carruth mentioned above. I guess I'm going to use taller frets on classicals from now on (the earlier cited experiment with the inserted taller fret probably allowed the insert to slide back and forth). I expect the relevant difference between nylon and steel strings is flexibility.
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Re: A "parasite" tone

Postby Massimo Milan » Tue Aug 30, 2016 2:32 pm

Bob Gramann wrote: I expect the relevant difference between nylon and steel strings is flexibility.


If so, higher tension strings should give some good result.
The first string set I tried was a "high tension" set, but I presume that the classification of low, normal and high tension is not standardized; maybe giving a try to high tension set by different brands......
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Re: A "parasite" tone

Postby Doug Shaker » Tue Aug 30, 2016 4:27 pm

I have had strange second notes when the nut slots did not slant properly from the front of the nut back to the tuners. If there nut slot had a high point somewhere in the middle of the nut, sometimes the string would vibrate with that as high point as the end of the string and sometimes it would vibrate with the sides of the nut slot (the front of the nut) as the end of the string.

The test for this was to take a credit card and press down on the string just in front of the nut slot, making the credit card edge be the end point of the vibrating string. If the second tone goes away when you do this, you can assume the problem is the slant of the nut slot. If this is the case, reworking the nut slots so that they slant back from the front edge would fix the problem.

It sounds to me like you have already checked out any issues at this level, but I felt like I had to mention it in case you haven't.
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Re: A "parasite" tone

Postby Bob Gramann » Tue Aug 30, 2016 5:21 pm

High tension is still nylon. I have high tension one mine. I couldn't really tell the difference when I changed to them.
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Re: A "parasite" tone

Postby Brad Heinzen » Tue Aug 30, 2016 11:48 pm

Any chance the is the 'zip tone' problem again? That can be really maddening to diagnose, and it always exhibits that same fretting behaviour (it goes away when you fret right at the fret). It's usually only the fifth, and especially the fourth strings in my experience.
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Re: A "parasite" tone

Postby Massimo Milan » Wed Aug 31, 2016 2:02 am

Brad Heinzen wrote:Any chance the is the 'zip tone' problem again? That can be really maddening to diagnose, and it always exhibits that same fretting behaviour (it goes away when you fret right at the fret). It's usually only the fifth, and especially the fourth strings in my experience.


"zip tone"?
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Re: A "parasite" tone

Postby Alan Carruth » Wed Aug 31, 2016 1:48 pm

There is a longitudinal wave in the string that is more or less analogous to a pressure wave in a long pipe. Ralph Novak called it the 'zip tone', and it's one of the reasons behind his 'fanned fret' design. Piano tuners call it the 'clang tone'. It's the sound you hear when you rub your finger along a wound string; you can get it on a plain string as well by using a bit of rosin on a rag. The pitch of the 'zip tone' is a function of the Young's modulus and density of the string, and the length. String tension has almost no effect on it with steel, and only a marginal one with nylon, so it's not related directly to the tuning pitch of the string. Generally the zip tone on a guitar string will be somewhere between the 7th and 8th partial.

The mechanism that drives this in plucked or struck strings is a bit complicated: what's important is that if the frequency of the zip tone is a pretty exact match to the seventh partial of the string the longitudinal wave will build up in amplitude to where it can feed back on the transverse vibration of the string. You end up with a string that makes two notes at the same time, which, since they're usually very close in itch, sounds like a fret buzz. The tell tale is that it happens on one string, at every fret: remember that the pitch of the zip tone is governed by the length, so it tracks the fundamental of the string as you fret it.

This effect is extremely sensitive to the mass of the string, so that even small change there can bring it on or cure it. For some reason nylon D strings are really prone to this; they all seem to be built with a core/wrap ratio that puts the zip tone close to the seventh partial. Since winding the string onto the roller tends to unwind the wrap and change the mass a bit, changing the way you install the strings can help, as can removing an offending string from the tuner and twisting it to tighten up the wrap.
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Re: A "parasite" tone

Postby Massimo Milan » Wed Aug 31, 2016 1:58 pm

Update.
Experiments were going on at lutihier's lab while we were discussing.
- A single steel 4th string was set up to pitch instead of a nylon, aaand....no buzz, no double tone but a clear tone.
- A single nylon 4th string was then set up to pitch, but instead to be tied it was fixed by simply three knots acting as a ball end
Aaaaaaaaaaaaand.......NO BUZZ! NO PARASITE TONE! A CLEAR HOLY NOTE! I still can't believe it's true, waiting for further confirmation. Thinking of it, I could......no no, I'll let you think about the possible explanation.
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Re: A "parasite" tone

Postby Bryan Bear » Wed Aug 31, 2016 2:31 pm

This is probably a dumb question but. . . do we know for sure that the effect was still present after the other 5 strings were removed but before the steel 4th was installed? By that I mean, did you test the guitar with only the old 4th string (no other strings) before you observed a clear tone generated by only a steel 4th string and subsequent test with a single nylong 4th string with the 3 knot anchor?
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Re: A "parasite" tone

Postby Massimo Milan » Wed Aug 31, 2016 2:42 pm

I'm waiting for more details about all the experiments, probably will go there next friday
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Re: A "parasite" tone

Postby Massimo Milan » Fri Sep 02, 2016 8:23 am

Last news, and good news.
Experiments included to try steel phosphor-bronze strings on the crossover, and nylon strings on an acoustic. Well, phosphor-bronze wound strings sound perfectly on the crossover guitar, while nylon strings generate the well known parasite tone on the western guitar.

Then two different D strings were put on the crossover, one D'Addario and one Aquila, the last being thinner than the first. Well the D'Addario sounded very bad, while the Aquila sounded significantly better.

So the problem was focused on the strings.
Nylon strings were not tied to the bridge of the crossover but fixed at the ending holes of the bridge by a knot: the parasite tone was reduced just a bit.

The Aquila strings were obviously chosen to go on with next tries.
But the most significative step was to twist on itself the string, ten-twelve folds, as to tighten the wounding, and while keeping it firmly twisted to fix it to the post and tension to pitch.
Gone. The parasite tone is completely gone on E and D strings and almost completely gone on the A string.
The plain nylon strings were substituted with ball end strings (some D'Addario EJ32) and that's all for now folks.

I have planned next tries with Thomastik "John Pearse Folk" strings, Thomastik "Classic N" and "Classic S" strings.
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Re: A "parasite" tone

Postby Alan Carruth » Fri Sep 02, 2016 5:09 pm

So it could well have been a longitudinal wave couple. Interesting.
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Re: A "parasite" tone

Postby Massimo Milan » Fri Sep 02, 2016 7:41 pm

More news.
after a warm up of the strings the parasite tone comes back thus confirming that it is a string problem.
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Re: A "parasite" tone

Postby Brad Heinzen » Sat Sep 03, 2016 12:08 am

Sure sounds like the 'zip tone' to me. I have no idea why it varies so much from guitar to guitar, but I've had a handful of really bad ones - maybe 4 guitars out of 50. On my guitars, I've always had the best luck with EJ4x strings, and the worst with Hannabachs. Augustines are somewhere in the middle. I've had guitars where the 4th string just screams with Hannabachs, but sounds perfectly normal with EJ46's.

On the occasional really bad guitars, I've always been able to get good results by twisting the crap out of EJ46's (tightening them to pack more windings in). Simply changing strings (to another set of the same type) has never worked for me - if the guitar exhibits this behaviour, it's always been completely consistent between different sets of the same strings. Different types of strings can give radically different results.
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Re: A "parasite" tone

Postby Massimo Milan » Sat Sep 03, 2016 5:16 am

Brad Heinzen wrote:...Different types of strings can give radically different results.


I am firmly convinced that, if for no other reason that the typical repertoire is not classical, a crossover guitar is not meant to be played like a classical.
I'm thinking of a hybrid set using say silk&steel E A D and nylon/titanium/carbon G B E
But I'l try before those unusual Thomastik sets: Classic N, Classic S, and John Pearse Folk .
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Re: A "parasite" tone

Postby Massimo Milan » Mon Sep 05, 2016 2:42 pm

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