JP6 w/piezo: Bad grounding? loud hum

[Chaka5150]

Wondering if anyone has had this experience using their JP's loaded w/piezo.

The Problem: I get a loud hum when muting my strings. even if i hit the switch on my JP for piezo only...the hum is still present.

My basic setup: I am using a stereo splitter box connected to my Axe Fx Ultra (mags routed to front input and piezo to rear input right) all Axe fx I/O configured properly etc. If i use the mono/piezo ouput of my JP no problems...Its not cables as i've swapped around cables to no end to eliminate that as the culprit; second I believe I've eliminated the Ultra as the culprit as disconnecting the input to the Axe fx stops all hum.

I know its not my pickups or cables. Is it the stereo splitter box? well I removed that from my chain and no different. so not the splitter box. what i should add is that when I remove one cable (for piezo) the hum is massively reduced. this is with and without the splitter box in the equation. It is not the ground lift switches on my gear as ive played around with those as well. not anything to do with high gain presets on my axe as my other guitar (Axis) does not require any noise gate in my preset. when using my JP and routing for stereo/piezo i need the noise gate to be on big time. Again, as mentioned above, If i use the mono/piezo output of my JP (thus removing dual routing-dedicated piezo/dedicated mags in preset) there is no hum from this guitar; similarly when I use my Axis there is no issues at all. I suspect ground problems/shielding issues in my JP.

Hope this makes sense.

 

[joe web]

it´s a grounding issue while using the stereo output or both outputs in parallel on the JP.
you have two different ground connections on the Axe which connect to the same guitar. so you get hum.
while using the the stereo output or both outputs in parallel, i would recommend a DI box (with groundlift) for the piezo signal or any other groundlift box / hum eliminator for the piezo signal in your setup.

i don´t know much about the Axe, but i think, that the input is buffered and there you have another preamp besides the onboard preamp of the JP and this causes grounding hum.

it´s just like using two tubeheads in parallel at the same time with the same guitar and use only a Y-cable to feed them with the signal - ground hum is the result.

isolate one of your signal chains and you will have a silent setup.

 

[Chaka5150]

Thanks for the info...that makes sense. I do have a Big shot aby box with a ground lift, and the funny thing is it is what got me started in the first place messing around with my current configuration. Initially I was trying to isolate what seemed to be sucking the tone out in my signal chain.

For some time I have found that when running my guitars via the big shot (which is uber convenient for having a dedicated tuner out etc) the tone is colored and by colored i mean a pronounced midrange honkiness(nasal quality) much like rolling off your tone knob on the guitar. So i started messin around with different cables and then removed the bigshot alltogether from the chain and voila! that was it. unfortunate really. but now i won't use it as it colors the tone too much, not sure if there is some kind of buffering going on in the box but it really affects my tone. possible flash of genius here (well Joe Web, you actually can take partial or even full credit here i may be able to use the bigshot after my stereo splitter box just for the piezo line to benefit from the ground lift off the Bigshot. I'll give it a try.

 

[Chaka5150]

quick update: tried using the bigshot aby for the piezo line only (coming from the stereo splitter box) to help eliminate some of the noise. It does help quite a bit, but there is still a hum there now about half as loud. I'm relatively happy about it but would like to see it go completely away. this seems to confirm, in part that it is due to using either both outputs of my JP or the stereo output (with a TRS).

here is a pic of what i'm talking about. I use output b to utilize the ground lift and ISO switch that seem to make a difference.

 

[joe web]

if there is still a hum....hm, i don´t know what to tell you now.
have you checked the wiring in the guitar? maybe a bad solder point is the reason for it.
or your stereo splitter is not working correctly.

 

[DrKev]

Call or email customer service and they'll sort you out.

In fact, if ever there was case where calling customer service is required, this is one!