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John Myung Bongo 4

Piezo issue

D

darren

Well-known member
Joined
Jan 18, 2005
Messages
193
Location
Toronto, Canada
Hi, all

I'm experiencing a very minor, yet very annoying issue with the piezo system in my JP7.

I'm running a stereo rig. I just made a new stereo cable (pretty sweet... Canare cable and Neutrik connectors) and while testing it out tonight through headphones, i noticed something i've never heard before.

When running in combined magnetic+piezo mode with each signal going to a different processor, i'm experiencing a very slight bleed-through of the piezo signal onto the magnetic signal. It's not dominant, but it is audible, especially if you hold a chord and flip the switch from magnetic-only to the combined (middle) position.

When i flip the switch down to the magnetic-only position, there's no piezo sound at all coming through the magnetic side, so i know it can't be the cable.

When the switch is in the piezo-only position, the magnetic signal is completely muted, and there is no piezo signal bleeding through to the magnetic side.

The magnetic signal does not bleed through to the piezo signal at all.

Again, this is a very subtle bleed through in the middle position, and i've checked and double-checked the cable with my meter, and it's totally fine. The only places where the two signals could possibly be getting crossed seems to be in the guitar.

Has anyone else experienced this?

Thanks for any help!
 
I should add that i'm going to test it tonight with a pair of mono cables plugged into both outputs, to see if it might be an issue with the mono/stereo switching.

If anyone else with a piezo-equipped Music Man could try theirs out and let me know if they get any piezo bleed-through in the middle position, i'd really appreciate it.
 
Well, i just tried it out running separate mono cables, and there is no piezo bleed-through on the magnetic channel. This leads me to believe there's an issue in the jack or the switching circuitry that leads to some "crosstalk" between the two channels when using the "mix" mode with a stereo TRS cable.

If there were a problem with the cable itself, i would imagine i'd be experiencing persistent crosstalk in both directions: i.e. i would also be getting magnetic signal bleeding through to the piezo channel as well. This is not the case.

I've tested the stereo cable, and it's totally clean, with each channel completely isolated from the others, and no mechanical noise from poor solder joints or broken conductors. I was patient and did good work. :)

If anyone else has experienced anything like this, i'd like to hear about it. I'd prefer to use a single stereo cable instead of a "dual mono" setup. Hopefully, you guys can offer some feedback, but i'll likely be giving EBMM customer support a call tomorrow and see what they think.
 
I just spoke to Steve in Customer Service, and apparently this is "normal" when running it with a stereo cable.

Not the answer i was hoping for, but at least now i know i'm not crazy. And my guitar's not broken. Maybe i'll have to modify my nice new stereo cable and make it dual-mono at the guitar end. :(
 
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