I found something interesting. I am not sure if it works with the JT Variax, but it sure did with my 700.
"Variax 500/700 Special Startup Modes
[Turn the Variax off by removing the batteries or the stereo cable]
1. Turn the volume pot up on the Variax in order to hear any audible feedback. 2. Apply power to the Variax with the model select knob in the up (save) position. 3. The Variax is now in the mode select state. Select a mode with the 5-way selector: 1st (neck) position - firmware version 2nd position - calibrate model select knob 3rd middle position- adjust string output levels 4th position - nothing 5th (bridge) position - nothing 4. Enter the mode by turning the tone knob to min and then to max. Mode Details Firmware Version 1. The firmware version is made up of 4 digits, for example 01.21. For each nonzero digit, the Variax outputs short, higher pitched tones to indicate the number. A zero digit outputs a longer, lower pitched tone. 2. When finished, the Variax returns to the mode select state. Calibrate Model Select Knob 1. The Variax outputs a long, low frequency tone to indicate entry into this mode. 2. The following steps apply only for a type 2 knob. The type 1 knob details will be detailed in a future revision. 3. Turn the model select knob from min to max to min. Repeat this until the Variax gives audible feedback. 4. When finished, the Variax outputs a short low tone followed by a short low, high, lowâ€¦ sequence followed by a longer higher tone. The Variax returns to the mode select state. Adjust String Output Levels 1. The Variax outputs a long, low frequency tone to indicate entry into this mode. 2. The model select knob determines which string level to adjust - High E = Custom 1 B = T-Model G = Spank D = Lester A = Special Low E = R-Billy The Variax outputs a short low frequency tone when one of these strings is selected to adjust. 3. Turn the tone knob to set the level. 4. ! Repeat steps 2 and 3 for each string. When finished, turn the model select knob to Custom 2. The Variax outputs short low, high, low, high, and low beeps after writing the updated levels to the flash and then returns to the mode select state."
The neat thing is that while the guitar is in this "mode", there is no processing whatsoever, and you will obtain that wonderful piezo sound (just like when you connect your acoustic guitar to a DI.
As long as you keep the pickups selector in the bridge position (which has no function on this mode) and the model selector in the save position (lifted), the piezi ar on and the volume knob functions as well.
What I liked most about this is that (at least in my Variax 700), the acoustic models have a big problem: the D string has to much mids (around the 500 hz) and without a proper equaliser, I simply cannot obtain a nice acoustic sound. I am also convinced that the batteries will last a lot more! :)
I hope this helped!