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JTV strings signal annoying compression

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Hi, one of my friends has a JTV-59 which he bought because he liked the Variax concept after seeing/hearing me playing with my Variax 700.


I tried his 59 and I noticed on all strings a remarkable and quite annoying sort of limiter/compression effect with every model available which affects in a bad way especially the attack of the notes (trying to pluck the strings with fingers the issue is even worse)..


But when switching from models to mag PUPs (which sound louder) the guitar sounds just perfect.. which thing makes me think that the guitar physical setup doesn't need to be re-done, and it's not the culprit of the models signal compression I mentioned above..


My old 700 doesn't have and never had this sort of compression issue.


Doing my searches I've read somewhere that a solution to get rid of the unwanted compression could be to lower the strings global level and turn up the models levels to compensate, and probably I will suggest this type of solution to my friend.


But if this should be the best solution (waiting for confirmation), I still wonder why it is necessary to do this type of adjustment with JTV, where it has never been necessary with my old tech Variax.


Official (but not exclusively) answers/ideas would be very appreciated.

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If re-flashing the firmware doesn't make a noticeable difference then....


It may have been a post or two of mine where Global String Levels were mentioned along with compression or more specifically a lack of dynamics. I have no inside knowledge, but I do have a degree in electrical and electronic engineering and I work in computing... so a little knowledge could have lead me to completely the wrong interpretation. Or not. I have a much better knowledge of measuring signal levels now and could probably prove it with some measurements; except we have a 3 set gig tomorrow afternoon and all the kit is packed up.


I first tried adjusting global string levels after following advice about how to get better acoustic sounds by  switching strings to 11s, and while the tone was better there was no dynamics so I starting thinking about why it wasn't that great and then about why global string levels would exist as a configuration at all. I thought about a few of the variables:

  • The resonance of the wood the guitar is made of
  • The gauge of strings players use - from Billy Gibbons 7s to Steve Ray Vaughan 13s
  • Playing style and picks varying from featherweight nylon to solid metal or stone
  • The sensitivity of the piezoelectric pickups 

Any of the above will give a significant variation in the signal level coming out from the pickups. The signal that then feeds into a modelling process that include pitch shifting and most significantly effects that depend on the level of the signal: such as how much resonance or body do you get. The modelling has to have a sweet spot in the incoming signal level - too quiet and the sitar won't get resonating strings, too loud and they won't stop.


To get the signal into that sweet spot with the wide set of variables I couldn't see any way to cope without putting some form of compression and or limiting place. But the consequence of that would be that if you had sensitive pickups and resonant wood (which is good - right?) and used 11s and played with stiff nylon picks or fingernails then you could be hitting that compression very hard all of the time. And the designers must have known this and put in an option to reduce the signal level before the compressor  that would affect all of the models - because the root cause is the physical attributes of the guitar and player. Global string levels was exactly this sort of control.


So I tried it and was quite shocked to discover that I had to reduce the lower strings down to -10db or more before I could hear a difference in the sound level from the guitar. So I turned it back up slightly and repeated on all the other strings; the top ones were more like -5db. I then played quite a few of the models and the acoustics especially had a lot more dynamics to them. The only problem with the method is that you have to guess because all you can hear is the results after going through a model and you don't know what that is doing to the signal.


If I was to repeat it today - or more realistically on Sunday - I would be using a Loudness meter that gives me peak and short term loudness and dynamic range figures and I could probably achieve a more balanced result across a range of models.


So my answer to your question is that I think the only reason that Global String Levels exists is to allow for compensation in the variables I list above, and that it was put there to fine-tune the guitar. The reason why they come from the factory set to 0db on all strings is that it is probably a relatively costly step to tune them for each guitar when the result will probably be wrong anyway because of point 3: the player.



Or everything I wrote above is complete nonsense. Neither psarkissian or anybody else from Line 6 to my knowledge has never commented on this subject but I would love to get feedback from the software design team on the subject.

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1 hour ago, Rewolf48 said:

It may have been a post or two of mine where Global String Levels were mentioned along with compression or more specifically a lack of dynamics.


Yes, confirmed, it was you the author of the afore mentioned posts I was referring to.


The logic behind your hypothesis seems solid and interesting.


I'm still wondering why the first generation Variax like my 700 electric doesn't have the same problem of the JTV.


So I thought that since the JTV piezos should be theoretically better compared to the old ones, and the piezo pre-amp should be evoluted too, which are the other elements that differ between the 2 Variax generations: the modeling engine, the tuning system, and the presence of mag PUPs on JTVs.


So apart from the compression which could happen pre-modeling (as you assumed), or maybe as part of the HD modeling processing, I have a suspect also about the tuning system..

and I wonder: could be that when no particular tunings are required the tuning system remains somewhat active and doubles the signal creating a sort of off phase relationship with the original one, similarly to what could happen when a DAW track monitoring is enabled and the hardware direct monitoring of the AI/multifx (like a POD) is enabled at the same time??

which thing as you know could affect badly the notes attack and impart a certain nasality to the resulting tone..


Anyway, I'll suggest to my friend (JTV owner) to do a FW reflashing, if it will not solve the issue I will suggest to try the solution kindly suggested by you, and if still necessary, investigate a little more the tuning system to see if it could be the culprit or not.


Thanks a lot for your contribute.

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  • 2 weeks later...

It would be good to know from Line6  where in the signal path the Global String Levels takes effect. I assumed it was on the output coming from the modelling but I see your thinking that it might be on the input. But worth a try and if you find it improves things for you, then all for the good. I seem to have a weak A string piezo and have reduced all other strings by -10db to -6db to get them balanced. Not noticed any effect on the sound but not really tested for that.

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8 hours ago, odersfelt said:

It would be good to know from Line6  where in the signal path the Global String Levels takes effect. I assumed it was on the output coming from the modelling but I see your thinking that it might be on the input. But worth a try and if you find it improves things for you, then all for the good.


It's my friend who owns the JTV (I own a 700), when I'll see him again in a few days I'll tell him what to try to do to improve his instrument response, based on what have been suggested in the previous posts in this thread.

I'll report the results when done.


8 hours ago, odersfelt said:

I seem to have a weak A string piezo


Careful cleaning of the piezo and its slot in the bridge saddle, plus turning the piezo 180° could solve some piezo issues..
it worked for me in the past

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  • 5 months later...
On 7/11/2019 at 3:46 PM, psarkissian said:

Follow the instructions on re-Flashing the firmware to the factory defaults.


I have had the exact same problem since I purchased my 2nd hand JTV. 


Did the re-flashing work for your friend?


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2 hours ago, sgreb said:

Did the re-flashing work for your friend?


Although it may seem incredible, since I wrote in this thread, my friend/student owner of the JTV has not yet tried to re-flash, otherwise I would not have forgotten to report the results here, which I will do when it is finally done.


If I had been him, surely I would have done the test immediately, since I use the instrument a lot, for pleasure and job, and I would not bear to play an instrument that does not respond as it should.


But he evidently gives less importance to the problem than I do,
or maybe he's simply lazy.


To be honest I still can't figure how a re-flashing could ever solve this type of problem, but since it has been suggested to me by "psarkissian" who knows surely more than I do about it, it would be stupid at least not to try.

After all except for some time, what else is there to lose?

If you try first, kindly let us know your results.

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6 hours ago, sgreb said:

Unfortunately it did not work. 


But damn it!

Thanks sgreb for reporting.

Unfortunately I don't have the opportunity to try other JTVs to make comparisons and see if they all respond in the same way (to the same player)..
who knows, maybe all JTVs in general respond in a normal way only in the hands of those players who use a very light touch.

If this is so, surely they would not be suitable for me as I have a very dynamic way of playing (going from delicate to strong), luckily my old 700 does not limit/compress my playing in any perceptible way..

I'll see if my friend will get the same disappointing result you had after the reflashing .. but honestly I tend to pessimism in this case..

He doesn't know it, but I feel a little guilty with my friend, after all I was the one who convinced him to invest money to buy a Variax (in origin he wanted to buy a real LP but he liked also a few other standard guitars), then he decided to take the JTV-59, assuming it should have been even better than my old 700, but it was not so, this is the simple truth.
Too much hassle to get a normal working instrument which didn't cost little brand new.
I wonder if there is a quality control check on the instruments that leave the factory.
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5 hours ago, klangmaler said:


You're reporting for half a year of a guitar that your friend bought...

Maybe it's time to make it a little more concrete, for example with a recording of the problem - otherwise it's hard to judge over it ;-)


I can not make easily recordings showing this specific issue since I don't own the guitar, and the owner who lives 20km away from me I see him at his home only once a week for a lesson of about 1 hour and a half, during which we play almost all the time.


However at this point I don't think audio demos are really so necessary, some who have replied previously in this thread clearly have already understood the problem very well (without audio demos), also because it is not an isolated case and has already happened in the same way to several other people.


As suggested by the service engineer psarkissian my friend will do a re-flashing at some point (hope soon), and if it doesn't work, he will try to follow the suggestions given in Rewolf48's post which seem very logical to me and I believe that most likely they can improve the functioning of the instrument.


Since not all JTV owners complain about the same problem, but only some of them, I wonder if some piezo sets and/or internal preamplifiers more powerful than others have been mounted on some JTVs, which would trigger an internal limiter/compressor more easily, thus denaturalizing the sound.


In any case, whatever the cause of the problem, I believe that the various checks on the proper functioning of an instrument and the necessary adjustments should be done by the factory before sending it to the shops, especially if the instrument is not cheap.


In this case I would say that if a functioning check has been done, it was quite summarily.

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