Ok, this has been bugging me for a while. I finally got around to recording the warble noise I hear on my jtv 69 when using alt tunings. This example was recorded direct, with no speakers on during the recording. I have the current version firmware version installed on my jtv. I start out with no modeling, using pickup setting 2. From there I turn on the modeling (spank, standard tuning) and scroll through the various tuning modes (drop d, 1/2 step, drop d flat, one step down and baritone).
I have tried dampening the strings behind the nut as well as dampening the trem spring. The warble remains. The guitar is tuned to standard using 10 gauge strings. The trem is not floating. I think the warble/pulse is clear to hear.
Let me know if you hear it to.