Jump to content
cruisinon2

Discovered Something Interesting About Piezo Crosstalk...

Recommended Posts

OK...I'll apologize for the length of this post up front.

 

The only nagging issue I have with my JTV69 is as follows:

 

Problem is limited to all the drop D tunings (drop D, drop Db, DADGAD, open D). 

Basically, when palm muting the open A string, and some fretted notes as well, with a high gain amp setting, I get some odd overtone(s) coming through...almost sounds like more than one string is being played...horribly muddy.
 
Easiest way to hear it is crank up the gain, and just do some palm-muted chugging on the open A string...if I toggle back and forth with the alt tuning wheel between standard tuning and drop D while chugging away on the A string, its terribly obvious.
 
I can work around it under certain circumstances by positioning my picking hand so that there's no contact at all with the low E string (which I kinda discovered by accident), but for some tunes contorting like that just doesn't work. Initially I had suspected that since avoiding the low E string seemed to fix it, that perhaps it had something to do with the piezo's sensitivity, picking up accidental noises just from resting my palm on the E string while playing. It never happens in standard tuning, or any of the other alt tunings...and this is what was nagging at me. Why some tunings, and not others??? And why only the various drop D tunings? I figured an overtly specific problem must have a specific cause. So I went into Workbench to do a little experiment....

 

I pulled up Lester-1, and I brought the A string volume all the way to zero. I then played just that string, carefully muting all the other strings down by the nut so nothing else would start ringing, also being careful not to touch anything with my picking hand but the A string. As expected, total silence.

 

BUT...as soon as I layed the palm of my picking hand across the rest of the strings, (normal palm-mute, "chugging" position) playing the A string now produced clearly audible notes. With that string's output at zero, the only possibility that I can see is that enough vibration is being transfered through my friggin' hand that is then propagating along the low E string to that piezo saddle (possibly others as well?). I suspect it's mostly by the low E saddle, because one's hand will rest mostly on that string almost by default, when palm-muting anything...mine does anyway.

 

It explains why this is only happening in the drop D tunings...when I palm mute and play the open A string, any resonance being grabbed by the low E saddle is then being detuned, and this has to be what's bleeding through. It also explains why it does not occur in any of the other tunings...in those cases, the low E piezo saddle is probably still picking up resonance from the A string, but since its not being detuned, is passes through unnoticed as the same pitch.

 
I'm no engineer, but I'm pretty sure that this is what's going on...the quesiton is, is there a fix? Do I have absurdly sensitive piezo(s)? Or is my right hand too dense? :P
 
Any thoughts would be appreciated....and thanks for reading if you managed to stay awake through all that!!

Share this post


Link to post
Share on other sites

There is also some crosstalk from one saddle piezo to the others.  They are not completely mechanically isolated.  This will produce some unwanted overtones especially when using alternate tunings.  Alternate tunings are never going to be perfect for this and other reasons. 

  • Upvote 1

Share this post


Link to post
Share on other sites

compliments for the clever experiment, and the subsequent deductions ..

 

If the palm of the hand transmits the vibrations to the other saddles, I believe that you don't have other chances than adapting your technique to avoid this issue..

More stubborn than clever...lol. It was driving me nuts. And I agree, its starting to smell like a technique issue.

Share this post


Link to post
Share on other sites

you could try to use fabric fingerless gloves in your picking hand for dampening the palm vibrations, who knows, maybe it helps..

 

Just currious to find out... :)

Share this post


Link to post
Share on other sites

you could try to use fabric fingerless gloves in your picking hand for dampening the palm vibrations, who knows, maybe it helps..

 

Well, it might be worth a try in the interest of curiosity...but I refuse to be seen in public playing  guitar with a glove on one hand, lol. Plus, I suspect that would deaden everything...including the string you're actually trying to play.

 

And if push comes to shove, I've got other guitars...I can always leave one in drop D ;). Nothing's perfect.

  • Upvote 1

Share this post


Link to post
Share on other sites

There is also some crosstalk from one saddle piezo to the others.  They are not completely mechanically isolated.  This will produce some unwanted overtones especially when using alternate tunings.  Alternate tunings are never going to be perfect for this and other reasons. 

 

This. I mess around with muting some strings in workbench and you can still hear sound when striking strings that are muted because it's resonating to the other pickups. It's VERY subtle and virtually invisible, but you can definitely tell it's there when you mute it like I did.

Share this post


Link to post
Share on other sites

This. I mess around with muting some strings in workbench and you can still hear sound when striking strings that are muted because it's resonating to the other pickups. It's VERY subtle and virtually invisible, but you can definitely tell it's there when you mute it like I did.

 

That may very well happen on some guitars, I guess...but if that were the case with mine, I would have expected to hear notes from the Workbench-muted string ringing through other saddles whether or not I was resting my hand across any other strings, but that's not what happens. I did all this listening through closed-back cans, cranked louder than I proabably should have...doing nothing but plucking the Workbench-muted string, touching nothing else resulted in complete silence, but the second I lay my hand across any combo of other strings, and play the Workbench-muted A string, it rings through loud and clear....and I'm not touching the saddles themselves at all during any of this. So if there's direct saddle-to-saddle communication, or vibes being transmitted through the bridge to another saddle, I'm not hearing it. It's all about where my hand is.

Share this post


Link to post
Share on other sites

On the JTV-89F you can unplug individual piezo cables to each saddle. I unplugged the 6th "E" string to check how much string crosstalk occurs through the other peizos. There is definitely some crosstalk. You can still here the low "E" through other saddles. It's quiet in comparison, but still there. I don't know how much effect this has on different tunings.

Share this post


Link to post
Share on other sites

Unfortunately, with alternate tunings, you are going to get some of the wrong tuning in the crosstalk.  I suspect this is the cause of "ghost notes" that some complain about with alternate tunings.

Share this post


Link to post
Share on other sites

http://line6.com/support/topic/111-make-your-variax-sound-100-better/?p=20716

I had actually remedied most of the issues with this physical altercation to my guitars I have pictures of them in this link it may help you also...  Good luck

 

I appreciate the response, but I've already tried all that. Its pretty clear to me whats going on from the poking around I did with muting the string in Workbench and positioning my hand various different ways. At least in this case, its not the nut or the bridge thats the culprit. The crosstalk is definitely propagating from the A string---> palm---> adjacent string and it's saddle. Its the only possibility, as I've corrected for everything else, ruling out one thing at a time. I can produce the odd sounds, or make them vanish at will, and its all about where I put my hand, changing nothing else.

Share this post


Link to post
Share on other sites

I don't know if this will be of any help or not, but here is my experience. I have a JTV-69s and I have been experiencing ghost notes when using the piezo pickups in alternate tunings. After sending a recording of this to Line 6, they agreed to have me send it back to them to have a look. You will not believe what they said was the cause of these ghost notes!


 


Official word is that my guitar was set up with the strings a bit too close to the mag. pickups. Oh, and I also had changed string gauge to 9 - 46 custom set. This was set up with the same string heights as on my Strat. They said that the magnetic pickups were causing the ghost notes while I was in Piezo mode. I have not gotten it back from them yet, but when I do, I will update this. In the meantime, for God's sake don't change your strings to a lighter gauge and keep them away from the pickup poles!! Interesting. They said nothing about these restrictions in their glorious marketing materials or their Pilots Guide. Amazing...

Share this post


Link to post
Share on other sites

I don't know if this will be of any help or not, but here is my experience. I have a JTV-69s and I have been experiencing ghost notes when using the piezo pickups in alternate tunings. After sending a recording of this to Line 6, they agreed to have me send it back to them to have a look. You will not believe what they said was the cause of these ghost notes!

 

Official word is that my guitar was set up with the strings a bit too close to the mag. pickups. Oh, and I also had changed string gauge to 9 - 46 custom set. This was set up with the same string heights as on my Strat. They said that the magnetic pickups were causing the ghost notes while I was in Piezo mode. I have not gotten it back from them yet, but when I do, I will update this. In the meantime, for God's sake don't change your strings to a lighter gauge and keep them away from the pickup poles!! Interesting. They said nothing about these restrictions in their glorious marketing materials or their Pilots Guide. Amazing...

 

Well, blended mags and piezos will certainly create a problem in alt tunings...you'll have competing signals producing different pitches, so that's not hard to believe at all. And since blending the signals is a feature, if something is wrong deep in the electronics somewhere, maybe this is the cause of your problem.

 

However, their explanation as to why this is happening makes absolutely no sense. I fail to see how the string's proximity to the mag pickups could possibly cause their output to be blended with the piezos. Ditto for the string gauge...the mag pickups neither know nor care what guage string is being vibrated in their presence. No way that's causing the issue either.

 

And why only with the alt tunings? The mag pickups are the same distance from the strings no matter what tuning you're in, so if that were the cause, you should have blending going on all the time...the models wouldn't sound right even in standard tuning, and I'm sure you would have noticed that, especially with the acoustics. As I said, if you blend the mags and use an alt tuning, you obviously will have problems...and that may very well be whats happening, but neither the distance to the pickups, nor the string guage caused it. I call BS on the "official" explanation...gotta be some internal electrical issue, bad board, etc.

Share this post


Link to post
Share on other sites

The pull from the pole-pieces of strat style pickups can cause very strange overtones.  Certainly possible that this would be audible on the piezo output.

Share this post


Link to post
Share on other sites

The pull from the pole-pieces of strat style pickups can cause very strange overtones.  Certainly possible that this would be audible on the piezo output.

 

I've seen his other posts...he's hearing two distinct pitches, which in an alt tuning could certainly be caused by the mag pickups' signal being sent to the output along with the piezo's. But I can't see the magnet pulling on the strings causing the two signals to blend, which  is what he said the "official" diagnosis is...unless I misunderstood his post.

 

I'm no expert, but if blending the outputs is the problem, doesn't that almost hafta be an electrical issue somewhere between the pickups and the output? A magnet too close to the strings by itself (assuming no other malfunctions) might pull them out of tune slightly, but how can it result in him hearing the kind of dissonance that you get when notes a 1/2 step apart are arguing with each other?

Share this post


Link to post
Share on other sites

Most mag pick-ups pass the current generated by the vibrating string through the pole pieces under all the strings. The effect that generates the current works in reverse too - a varying magnetic field can cause a string to vibrate, but at a low level because there are a lot of losses. Unless you pump up the current using an Amp circuit in which case you have a Sustaniac. The effect in both ways is proportional with distance, so the closer string and pickup the more it happens and the further away the less it happens.  The two sets of coils/magnets in Humbuckers will generally cancel each other out which is why it is most noticeable on single coil pickups.  

 

"And why only with the alt tunings?"

 

This is a physical sympathetic vibration thing (with or without the magnetic effect) - you play a bottom E for example and all strings will try to vibrate at the same frequency - none will achieve it, but depending on what you have fretted some strings will vibrate at the first or second octaves.  

 

So play just a bottom E and the top E will vibrate on E as well without you touching it, but you don't notice it because you can hear the fundamental E and sympathetic vibrations are completely masked because they are the same as higher harmonics on the plucked string.

 

Now Alt tune the bottom string down to Drop D.  The guitar is unchanged, the physical sympathetic vibration is unchanged, you played and E and the other strings are vibration to E, and because they haven't been alt tuned you will still hear that E, but the fundamental note you are hearing is the alt tuned D so the little bit of E doesn't go so well any more.

  • Upvote 1

Share this post


Link to post
Share on other sites

Most mag pick-ups pass the current generated by the vibrating string through the pole pieces under all the strings. The effect that generates the current works in reverse too - a varying magnetic field can cause a string to vibrate, but at a low level because there are a lot of losses. Unless you pump up the current using an Amp circuit in which case you have a Sustaniac. The effect in both ways is proportional with distance, so the closer string and pickup the more it happens and the further away the less it happens.  The two sets of coils/magnets in Humbuckers will generally cancel each other out which is why it is most noticeable on single coil pickups.  

 

"And why only with the alt tunings?"

 

This is a physical sympathetic vibration thing (with or without the magnetic effect) - you play a bottom E for example and all strings will try to vibrate at the same frequency - none will achieve it, but depending on what you have fretted some strings will vibrate at the first or second octaves.  

 

So play just a bottom E and the top E will vibrate on E as well without you touching it, but you don't notice it because you can hear the fundamental E and sympathetic vibrations are completely masked because they are the same as higher harmonics on the plucked string.

 

Now Alt tune the bottom string down to Drop D.  The guitar is unchanged, the physical sympathetic vibration is unchanged, you played and E and the other strings are vibration to E, and because they haven't been alt tuned you will still hear that E, but the fundamental note you are hearing is the alt tuned D so the little bit of E doesn't go so well any more.

 

All of that I'll buy...makes perfect sense they way you've explained it, and obviously you know more about this than I do, lol. Like I said, I'm no expert.

 

But L6 has apparently told him that the issue is one of blended mag and piezo outputs, and that's what I don't understand. Is it not possible to completely isolate the mag's output from the piezo's? Unless you've gone into Workbench and deliberately created a model that blends them (which can give you some really cool tones blending the acoustics with the single coils, btw), why would the mag output be bleeding through if you haven't "told" the guitar to do it? If you can't totally choke off the mags when using the models, I would think that just about every Variax would be useless in alt tunings. What am I missing?

Share this post


Link to post
Share on other sites

The close coupled mag pickups could have been causing crosstalk between strings.  I would wait to hear what he has to say when he gets the guitar back though.

Share this post


Link to post
Share on other sites

I've enjoyed reading all of your posts. What really intrigues me is that when I did all of my research before purchasing the guitar, nowhere did I hear mention the very problematic nature of this setup. Now, I do not know if other systems (i.e. Parker, Godin, Peavey AT100, PRS) have similar issues. If they do not, then wouldn't you think Line6 would have a responsibility to deliver a system that works. Imagine if you purchased a USA model and had the same problems?!? At least my investment was not at that level. I guess I wish I could hear from more folks who have a JTV that works exactly as advertised. I have not had that experience yet, and I've been through two of their guitars. Kinda like the forum member from Australia whose had multiple "flawed" guitars.

Share this post


Link to post
Share on other sites

Some more detail. My ghost notes were occurring when I was in Piezo mode, and in Workbench the settings were NOT in a blend mode with the magnetic pickups. 

Share this post


Link to post
Share on other sites

alot of those other systems/guitars you mentioned either use midi or just direct output the piezos... they don't have the analog alt tuning or digital models.. so not apples to apples.

Share this post


Link to post
Share on other sites

From what I've found, crosstalk would not be a correct terminology.

The tests I've made points to sympathetic vibrations from other strings,

especially if it's an open string. And that sounds thru its piezo and signal path,

and gets process like everything else.

 

Crosstalk, sympathetic vibrations, similar things the terminology tends to be used

interchangeably. Hope I clarified a bit.

Share this post


Link to post
Share on other sites

I would define "Crosstalk" in this context as any signal from OTHER strings getting into a Piezo.  This is unwanted and it doesn't hurt much when you are not using Alternate Tunings.  There is going to be some of this due to Mechanical coupling between saddles.  This will cause some unwanted artifacts with some alternate tunings since the alternate tuning algorithm is applied to all of the signal that gets into each Piezo pickup.

Share this post


Link to post
Share on other sites

O.K. the guitar is back from Line 6. Guess what? IMHO they did not fix anything. It sounds exactly the same!! Again to recap how I test it. (and I hope I am missing something)

Tones on all magnetic pickups  -  great. (remember, this is coming right off their bench and set up the way they say it is supposed to be)

 

Piezo mode. On the Alt. Tuning Knob it is set to Standard. On the model knob, set to Spank  -  Spank model and all others sound perfect. No ghost tones anywhere. 

 

In Piezo mode, turning the alt. tuning knob to any other setting, say "Blues G", I get double tones on the High E and G strings. Note: I get the multi-tones even when I pick the one string with my hand laying over all the others. This rules out the sympathetic response that was mentioned earlier. 

 

I will experiment a bit more. Recheck the settings in the Workbench and make sure nothing is set up to blend with the magnetic pickups. I am open to ideas - other then hitting something with the guitar!!

Share this post


Link to post
Share on other sites

O.K. the guitar is back from Line 6. Guess what? IMHO they did not fix anything. It sounds exactly the same!! Again to recap how I test it. (and I hope I am missing something)

Tones on all magnetic pickups  -  great. (remember, this is coming right off their bench and set up the way they say it is supposed to be)

 

Piezo mode. On the Alt. Tuning Knob it is set to Standard. On the model knob, set to Spank  -  Spank model and all others sound perfect. No ghost tones anywhere. 

 

In Piezo mode, turning the alt. tuning knob to any other setting, say "Blues G", I get double tones on the High E and G strings. Note: I get the multi-tones even when I pick the one string with my hand laying over all the others. This rules out the sympathetic response that was mentioned earlier. 

 

I will experiment a bit more. Recheck the settings in the Workbench and make sure nothing is set up to blend with the magnetic pickups. I am open to ideas - other then hitting something with the guitar!!

 

Sorry to hear that, but I'm not surprised. Their diagnosis made no sense in the first place.

Share this post


Link to post
Share on other sites

Regarding string gauge,....

 

If you want to use 9's, that's okay,.... but you'll need to take it to a guitar tech to have the

set-up adjusted for that gauge set. When you change gauges, you change the tension,

when you change the tension, the set-up is off and needs to be adjusted.

 

That info might not be in the brochures, because it's just a common aspect of all guitars.

Change anything that alters the string tension, and you alter the set-up. It's like that on all

guitars, not just JTV's.

 

Also, climate of your location also affects the set-up. When you get a guitar back from a

distant shop, the set-up should be done with your location in mind, so give it a couple days

or more to settle in. If it is still a little off, take it to a local guitar tech for that final dial-in.

 

 

Share this post


Link to post
Share on other sites

Regarding string gauge,....

 

If you want to use 9's, that's okay,.... but you'll need to take it to a guitar tech to have the

set-up adjusted for that gauge set. When you change gauges, you change the tension,

when you change the tension, the set-up is off and needs to be adjusted.

 

That info might not be in the brochures, because it's just a common aspect of all guitars.

Change anything that alters the string tension, and you alter the set-up. It's like that on all

guitars, not just JTV's.

 

Also, climate of your location also affects the set-up. When you get a guitar back from a

distant shop, the set-up should be done with your location in mind, so give it a couple days

or more to settle in. If it is still a little off, take it to a local guitar tech for that final dial-in.

 

Any thoughts on the crosstalk issue?

Share this post


Link to post
Share on other sites

Regarding the palm mute,.... which version firmware do you have loaded in? 

Version 2.00 program has a routine in it for palm muting.

Share this post


Link to post
Share on other sites

Regarding the palm mute,.... which version firmware do you have loaded in? 

Version 2.00 program has a routine in it for palm muting.

 

I'm running 2.0. This is a totally different, very specific problem. Affects only the drop D tunings. Palm-muting the open A string results in some weird overtones coming through.The original post all the way at the top of this thread describes it in great, gory detail. No point is typing it all again here, but here's the Reader's Digest version:

 

In short, the low E saddle/piezo is hearing the A string. I verified this by turning A string's volume to zero in Workbench, and then compared plucking the A string with no palm muting vs. resting my picking hand across the strings (in typical palm-muting fashion), and playing that A string again. With no palm-muting and the A string's output at zero, I hear nothing...total silence. With palm-muting, and A string's volume still at zero, I hear clearly audible notes. Only explanation is that one or more other piezos are picking up the A string's vibration through my hand being in contact with, in particular, the low E string. Hand placement is the only variable in the equation.

 

If I contort myself so that my hand is not touching the low E string at all, no odd sounds...but this is easier said than done.

Share this post


Link to post
Share on other sites

I have a Variax500 fitted with graphtechs which was working fine. Yesterday i  found I had a simila problem with alt tunings. i discovered My D string was being picked up (albeit quetly) from the Low E piezo and A piezo .The low  E was being heard in drop tuning presumabley though the adjacent A piezo. 

I think my problem may be because the ground feed to the vax electronics is not good, so effectivly two piezos are in sort of series and even if one of them is muted, the signal from it will be added to the active piezo. There appears to be one ground for VDI on the ribbon and another for analogue connected to the bridge screw. Im going to make sure both are good. I'm sure when i tested it originally I had no crosstalk from each of the piezos

Does this make sense to anybody?

 

I noticed from the variax schematic that the piezos all go through a 10k resistor and that the ground ( fed from the out put jack unit is labeled screenpaint ground which leads me to beleive that the original idea of putting the wire under the bridge screw connected it to the bridge and the screenpaint which runs all over the cavity. Not sure if similar thing is on JTV. When I took my bridge off i noticed my ground wire had broken.

And it was all going so well- I hoping the answer is a simple bad ground

Share this post


Link to post
Share on other sites

IMHO - Mechanically coupled adjacent string piezo saddle crosstalk is the "limiting factor" for accurate DSP created Alt Tunings on All Variax's 

 

The Graphtech Saddles have a wider surface area that reacts to any vibrations - (including adjacent strings)which means Variax Alt tunings will suffer odd sounding anomalies compared to a Variax with stock factory LR Baggs piezo saddles - 

 

The ultimate expression of focused vibration piezo PU saddles technology is sold by RMC pickups in Berkley,CA  - this is what the high end Godins with 13 pin Synth Access employ    

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×