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My new JTV-69 has bad modeling

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Hate to wade in here, but I still have a Roland GK2 Midi Pickup and the Roland GI10 midi interface. They are 2 totally different technologies.


In midi, the "note on" signal is the "trigger" -- it only detects that a note is "on", and the velocity or volume of the attack. In keyboards where midi was developed, the key was the note on trigger, and the striking velocity was, well the velocity of the note. Which key was hit was the note (or frequency) value, and when you released it, the note off midi value was sent. the midi module or synthesizer takes it from there and generates the actual audio signal.


Electronic drums use the trigger and velocity only, and you route each drum trigger to the drum module, each assigned to a particular drum sound and cymbals etc. Even in my Roland SC-55 and SC-88 modules, midi channel 10 is the default drum channel. Each note value is a different drum or percussion sound - pretty ingenious.


The way guitar synths and midi pickups work is they are hex - or 6 individual pickups that sense (in theory) only their string -- which is why you have many conductor pin jacks. It is actually taking the audio signal -- and it could work if piezos were used as well, again - some guitars with piezos have the many pin cables for a synth module. The interface has to decide for each string that there is a note present and its relative strength to generate a note on and velocity value, and also has to analyze the frequency to decide what note value to put out, and then decide when the note stops. It generates midi data which the synth module then puts out an audio signal for a trumpet or piano, or guitar....


All this has to happen in as near to real time as the processing can manage. In my experience with it, it tended to lag, as there is a lot going on before it ever gets to the audio output. They get fooled easily by harmonics, overtones, and string noise that is the bread and butter of a real guitar. I've heard some really well done midi or synth guitar, but it takes a lot of effort and quite a change in technique. The notes you hear are not the guitar's actual signal, but the module's voices that were triggered by the guitar's generated midi signals -- Note On, Velocity, Note Value, Note Off. With mine I was always fighting spurious notes. I did a few midi sequences with it, but never took it out live.


I have about 3 midi guitar examples on my midi site if your interested -- they're in the country section. Most my sequences are Beatles, Billy Joel, Steely Dan etc...


The variax is a DSP -- digital signal processor - it takes the actual vibrations of the strings and modifies them to make them sound like different guitars, but not like a drum, or a piano. The 6 piezos do put out 6 individual signals and each is processed within the guitar then combined into a total signal and send out the jack analog in the 1/4" output, and digitally down the VDI cable. The 6 individual string signals can be processed to increase or decrease their frequency by set amounts, which is why they can achieve the alternate tuning, and by differing amounts on each string to get open tunings and such. The piezos grab the signal at it's most basic, but does capture a bit of the body of the guitars -- my 59 and 69S models are damned close to each other, but not identical on the same patch, IMO.


Anyway, the processing in the internals of the guitar itself combine the total signal. To try to break that out would be possible, but it would take a total redesign of the whole DSP of the guitars. I don't think that's very likely. It'd be easier to add a midi hex pickup an run it into a guitar synth, like those who have done it already. Variax users like us are a fairly small subset of guitar players, and those who use guitar synths are an even smaller subset of guitar players, so Variax players who also do synth guitars is a smaller still subset of a small subset. I'm kinda doubting there's a huge market out there for it, so I'm doubting they'll tear apart a perfectly good design and do redesign for a very very small market segment...


My 2 cents...



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The other MAJOR reason for using Piezos is that they pick up each string's vibrations individually.  Can't do that with a Mag pickup.


That will come as a big surprise to those who own Roland 13-pin systems.  Given that piezo pickups suffer from vibrational crosstalk, there's an argument to made that a hexaphonic mag pickup can yield better isolation.  I think the choice of piezo pickups is more a matter of design aesthetics and cost savings.

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I still don't think it has anything to do with cost savings.


No modeling guitar uses triggers, midi signals, or any synthesis. That's why they're called modeling guitars, and not synth guitars.


The point is to recreate the tone of certain guitars, not to sample different tones of guitars.


Any guitar already has the required sound needed to use as a basis to simulate the sound of multiple other guitars, it's just a matter of capturing the sound of the strings before all the coloration of going through normal magnetic pickups, electronics, and tonewood things.


Piezos and the Roland pickup help get the sound from the string.


The piezos do get the sound individually, but there are hex magnetic pickups like the roland pickup out there.

It's just a question of which is a better reference point?


the piezos will yield a flatter broader frequency response, but have limitations/artifacts (Your hand blocks vibrations normally traveling from the string to the piezos when palm muting, making it sound muddy/Piezos are more sensitive to vibrations on the guitar, which can cause unwanted sounds in the signal)


the magnetics can be designed to have a broad and flat response, but not as well as the piezos, but you will exhibit none of the artifacts piezos bring. Your tone will sound less spot on but palm muting will sound better.



Either way, if it was trigger/midi/synth based, none of the pinch harmonics, artificial harmonics, and other nuances of your playing would show up in your tone.


No one is going to buy a synth guitar to replace their real guitar. The whole point is that it's an actual guitar, but it's replicating the sounds of multiple different guitars with the accuracy they can establish.

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