Fixing a faulty Variax model selector

Swiss knife of guitars, with minor flaw

The world of technology is in incredibly fast and constant move. I’ve got my first cellphone in 1996, an Ericsson 198, bulky as brick, with 2 rows LCD text screen. If somebody would tell me that I will watch movies, navigate in almost any places, create photos/videos, make video calls or even use its successor as a guitar effect and recording device 18 years later, I would rolling on the floor laughing…
While such a quick and thorough change in guitar technology isn’t so obvious yet (well, effects and amps are progressing much faster), there are clear signs of the challenge for luthiers and guitar techs to keep up with current digital technology. More and more guitars released with on-board digital components and if we consider Line 6 Amplifi that developed to use its full capacity only controlled by iPhone or iPad, there’s no doubt that a “brave new world” is approaching – like it or not.

Line 6 is a highly acknowledged name in guitar industry. Their POD digital multieffects and Spider amps are in the upper segment in view of the quality while the prices are yet relatively affordable for many players. They are experts of digital modeling technology and pioneers of modeling guitars producing the Variax series.

Digital modelling has come into fashion with the downsized high performance processors. It allowed to handle the high computing demand real-time tasks of busy audio signal processing with practically unnoticeable lag and acceptable quality in a compact unit.

Modeling means a simulation of the whole (or partial) audio signal chain based on the physical properties of components. The simulation software runs on an embedded processor called DSP (Digital Signal Processor) that is developed especially for audio purposes.
Of course, no simulation is equal to the real things. Real life phenomena are mostly so complex that a perfect algorithm would have too many variables and too complicated calculations. Modeling simulations use simplified approximations instead that could provide good enough result – but they are never perfect. People with trained ears and high expectations will surely notice the differences, especially in certain way of use. Otherwise the state-of-the-art modeling DSPs are practically good enough for most purposes. Moreover, some top quality gears, such as Kemper and Axe-Fx can satisfy even the most meticulous pros – but those systems are beyond the everyday players budget.

Line 6 products

Line 6 products

After the success of a couple of effect processors and modeling amps Line 6 came up with the idea: why don’t we drop the DSP into the guitar itself? A dream of many guitar player can come true: having multiple famous vintage or modern guitar tones in one axe!

During the development the research team did a thorough analysis of the physical parameters of the guitar components they wanted to include in the models. It covers a full spectral evaluation and testing the dynamic changes of attributes as well. Each model has its own algorithm  to deliver the desired tone in real time, with its dynamic characteristics. There are sub-processes for every single pickups and their combinations, for the different resonance characters of woods, etc. Such structured design allows the users even to define their own custom models, combining the components into wide selection of various tones.
The DSP designed to run those algorithms with sufficient speed and quality – and of course, to keep the production costs low (of course, such compromise always limits the capabilities).

The first Variax guitars were “DSP only” instruments. No traditional pickups, just a piezo in the bridge. That piezo hex-pickup is rather a sensor than a normal pickup, similar to the MIDI-converters made by Shadow, Roland, Graph Tech and others for guitar-to-MIDI devices. Signal of each string picked up individually as a source for processing.

When I tried the first Variax series, neither the tones, nor the design impressed me much. Their sound wasn’t really “alive” for me and the awkwardly blank look induced the feeling of ‘toy guitars”, although they were okay guitars. Especially I didn’t like the acoustic models. Well, many pioneering technologies bring up similar “tried hard but not good enough” impressions in their early childhood, but usually they got matured as the second generation released.

This is exactly what happened with Variax.

Second generation Variax guitars

Second generation Variax guitars

The second series of Variax guitars got significant improvements. Learned from the customer’s feedback about the flaws of the first models Line 6 realized that it isn’t enough to manufacture an instrument in Indonesia that feels rather like entry level synth-controller than a real guitar and rely only on the DSP, because the guitar community is stubbornly conventional.
To build a more appealing axe LA luthier James Tyler became the designer of the next series (JTV=James Tyler Variax) that are real working guitars with the addition of digital models – and they are cool!
Tyler is an acknowledged guitar builder and he designed the JTV series focused on the modeling yet to keep it a fully equipped instrument. The initial product line included 3 different guitar models: JTV-59, inspired by Les Pauls, JTV-69, a Strat-like axe and JTV-89, a kind of typical metal-guitar – I’ve owned this one for more than a year. The selection later updated with some more versions, as you can see on the image above.

Line 6 was smart enough to duplicate the selection by having a relatively affordable series (retail price about $1000-$1500) made in Korea and a high-end US made “custom shop” version, of course for way more bucks ($4000-$5000). My JTV-89 was a Korean-made and it’s a pretty decent guitar. It has reverse tuning gears, fast, slim Ibanez-style 3-piece maple neck, mahogany body, two powerful, metal-oriented high output pickups, Graph Tech TUSQ nut and Tyler wraparound bridge. A replaceable Li-Ion battery installed in the back is able fuel the electronics up to 12 hours.

My JTV-89 Variax

My JTV-89 Variax

The evolved Variax sports dual-core processor to handle much more complex tasks. For the best sound quality it combines high definition A/D-D/A converters and low-noise analog circuits. The signals from the L.R. Baggs Radiance piezo hex pickup are digitized by the 24 bit A/D converter. The processor applies all the numerous parameters of the model (interaction of the pickups, pickup position/height, magnetic attributes and nonlinear characteristics, type of wiring/pots/caps and the physical properties of the simulated body) on the digital data stream. There is no noticeable lag, all happens in real time. The D/A converter turns the bits and bytes into audio signal again and sends it to the output.

There are 23 type of guitar models including 6 and 12 string acoustics, banjo, resonator and even sitar. Most of them have several different settings. I found them quite impressive and convincing, only the 12 string models sounded a bit “artificial” for me. Another issue that most hard rock/metal players will face to: the system cannot reproduce properly the dampening with the right hand on the bridge. Again, it sounds less “alive”, doesn’t really “bite” as it should.
Other than that, it fits to virtually any style. The icing on the cake is the alternate tuning: 10 commonly used tunings included with the factory presets.

Variax Workbench

Variax Workbench

Moreover, the guitar can be connected to a Windows or Mac computer via USB with the included interface. Installing the Line 6 Workbench software (it needs to install the Line 6 Monkey software first – honestly, it wasn’t a smooth sail for me on my Macbook Pro, I spent a few hours with support to try to work it out) opens close to unlimited ways to extend the tones, because all parameters can be changed and combined.

We can say: the Variax is the swiss knife of guitars.
Model selector knob

Model selector knob

The control layout cannot be more simple – kudos to Line 6 designers!
There are usual master volume and tone pots . Two additional knobs are the model selector and the tuning selector. Those switches combined with the pickup selector multiply the choices. You don’t need any display, LED or other visual aid, the knobs are marked with the name of the models/tunings and lighted when engaged. After a few hours of practice it feels natural to use.
The selectors are not really the well known rotary switches, neither pots. The proper term is digital encoder. It has a couple of different positions, each one sends its own digital identification code to the processor. The model selector is similar to a standard pot knob, except it has the model names on it and a LED on the tiny circuit board of its base to light up the choice.

Li-ion battery of the Variax

Li-ion battery of the Variax

When I plug the jack into the standard guitar input, it turns on the battery and activates the standby mode of the DSP.
Without turning the models on, I can play the Variax as standard guitar using the magnetic pickups.
To engage the modeling mode I need to press the model selector down and release it. The micro-switch on the encoder shaft sends a signal to the micro-relay of DSP. The relay physically disconnects the analog wiring from the output and connects the DSP instead (I can’t mix the two signals). The delicate “click” of the relay is clearly audible.

Activating the DSP by pressing the encoder knob

Activating the DSP by pressing the encoder knob

When turned on, selecting the model is done by rotating the knob. Momentarily pressing and releasing the knob again will turn off the DSP and reconnect the analog circuit by the relay.

The tuning knob works similar way rotating it, the only difference is that the function is activated together with the model selector.

Guitar or computer? The heart of the Variax.

Guitar or computer? The heart of the Variax.

DSP lives here

DSP lives here

Within a the picked model the five way switch can activate different pickup combinations or even different instruments- for instance, the Strat simulation works the same as the normal Strats, while the acoustics selects different type of guitars.

It’s quite easy to get familiar with it, I had no problem to use it.

The whole setup is apparently a well designed and manufactured system. Well, at least, it seems to. Yet it isn’t perfect.
Some Variax owners experienced a very annoying problem: the activating function of the encoder works erratic. Researching the forums I’ve found it’s a common problem of that encoder design. The issue also known as “sticky selector” or “sticky knob”.

The symptoms are the following: after a couple of months of use engaging the DSP by pressing the knob needed more and more force. Eventually, it became impossible to activate the DSP. All attempts were vain.

First I suspected the encoder contacts. I pulled the knob off, took the electronics apart and removed the encoder.

Based on the numbers on it I did my homework with Google and found it’s a korean made Belton BTDS20HPT encoder (if you need to replace it). I tested it and checked the functions – it looked okay. Just in case, I sprayed some DeoxIt contact cleaner in it. I put together the guitar and tried… it worked! What a relief!

The encoder

The encoder

My happiness didn’t last long. The same problem happened again soon. More research on forums has proven that it’s a common issue.

Actually, the problem is a simple mechanical flaw: the internal part of encoder knob is all plastic, apparently made by injection molding. It has a sleeve that accommodates the truncated cylindrical shaft of the encoder. The sleeve is conical, wider at the open end and tighter inside. It intended to hold the knob on the shaft by the friction of the conical sleeve. But there is a design issue: in its normal position the shaft doesn’t go all the way up to the end of the sleeve. there is a small clearance over it.

The shaft is short and can't go all the way up in the knob

The shaft is short and can’t go all the way up in the knob

The conical sleeve - it can't keep the knob in the right position

The conical sleeve – it can’t keep the knob in the right position

If the plastic is strong enough to keep its shape and size in order to hold the shaft in fixed position even after several thousand of use, there’s no problem with the design. Unfortunately, it seems the plastic is weaker than it should be.
The repeated pushing on the knob slowly forces the conical sleeve to open up allowing the shaft to move upward, namely the knob will get closer to the base plate at the bottom.

To activate the on-off micro-switch the encoder shaft must move a certain distance – smaller movement can’t work. That is exactly what happens when the knob will slowly crawl deeper on the shaft because of the weak sleeve and reaches the position where its bottom contacts the base plate BEFORE the shaft moves enough to activate the micro-switch!

Emergency workaround: you need to pull the knob to force it back to the normal position – it can work again a few times but the whole trouble will repeat soon. That’s not going to work on a gig.

It should be fixed.

My idea was to extend the shaft until it will be long enough to touch the top of the knob while it’s in the desired position to avoid the crawling. I needed to figure out how long the extension should be, but I couldn’t take any precise measurement since I had no idea where is the proper original position by factory settings and where it ended up. Usually I prefer the rather accurate engineering approach, but I have no problems if the troubleshooting can be done by trial-and-error more quickly. 🙂

Punched disc from credit card

Punched disc from credit card

Macgyver-project started. I punched out some tiny discs from an expired credit card about the same diameter as the shaft. To fit to the truncated shape I cut a segment from each.
First I tried to use superglue with accelerator – but the result was a disc stuck on my finger instead of the shaft. The end of the shaft is slightly curved, I needed something else to fill the gap.

Next came the hot glue gun. That was the right choice. It can fill the gaps and it’s slightly flexible, yet strong enough.

The Ultimate Weapon :)

The Ultimate Weapon :)

Of course, one disc wasn’t enough. Finally, I ended up with 4 discs glued to the top of the shaft.

4 disc extension on the shaft

4 disc extension on the shaft

The result surely won’t get a design award but it worked well, no issues since I fixed it.

Honestly, I was slightly disappointed. It’s a $1000 instrument, with a really annoying functional failure that makes the main features of the guitar unreliable, sometimes even useless. Some of the guitar players might be able to fix it, but many others won’t. I haven’t heard about if Line 6 ever addressed this issue. I’m pretty sure that the knob is a very cheap part and an improved replacement can easily solve it.

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4 Responses to “Fixing a faulty Variax model selector”

  1. Thanks, you saved my day.

  2. I am experiencing this trouble too.

    Would it not be easier to poke some padding material into the cavity of the knob itself rather than lengthening the shaft of the encoder?

    That would make the knob sit higher??


    • Well, I’m not sure. Probably you can do that, but it was more easy for me to access the shaft than the inside of the knob.

      • hiya, just came across your article and was hoping you could advise.

        basically i have a JTV59 variax, and the problem you described is similar but not exactly the same. was wondering if your fix would work for this also (just your opinion, not holding ya to it!! he he)

        basically, i have no prob activating the DSP (i can select guitar models no prob)

        prob lies with my alternative tuning knob, when i turn it, it becomes erractic and doesn’t select the tunings (almost like its not reacting to the change in position (takes about 5-10 mins for it to start behaving as normal)

        i’ve checked over my workbench software and reloaded the firmware to no avail.

        was thinking it might be the prob you mentioned?

        any help you can give is greatly appreciated, line 6 offers no servicing in the UK anymore so i’m stuck

        john paul


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