Peizo grounding question

Drew · #1 07-24-2002, 02:23 PM

so i broke my new 2027 out at a gig... The thing sounded unreal- more balanced and smoother than the 7620 i'd been playing. However, while i was running the magnetic pickups into my amp and the peizo directly into the board, i'd get these horrific buzzes whenever i switched over to the distorted channel of my amp- it wasn't a problem while playing, really, but for staccato riffs and the like, it was pretty irritating. At first i just thought it was sloppy shielding (irritating, but a fairly simple fix), but after a few songs i remembered hearing something about grounding issues with multi-amp setups, so i pulled the peizo patchcord and ran it all through one amp- problem solved.

The problem is, of course, the peizo sounds more like a singlecoil than an acoustic through my amp's clean channel (mesa/boogie). so, i LIKE going into the board. I know there are ways to fix this this- something to do with running off isolated power sources, i believe. However, i can't for the life of me remember. I don't remember the exact electrical setup of the place; i know my amp and the board were in different outlets, but i don't know if they were on the same loop or not. I can check thursday- it's a weekly gig. If you could suggest anything (plugging into the same outlet, running through a preamp before the board, etc), tha'd be awesome. thanks,

-Drew

Gresh · #2 07-25-2002, 04:40 PM

Look in the back of your Mesa and you should see a ground-lift switch. Use it. You have a ground loop going on as you alluded to in your post, very common when bi-amping. If you don't have a ground lift, then I would give Mesa a call and explain the problem...guarranteed someone will have a solution for you.

Brad

RSVampire · #3 07-26-2002, 01:55 AM

I 2nd Gresh.

vaijem777 · #4 07-26-2002, 11:13 AM

Now...to expand on this topic:

I'm running my EB/MM JPM's piezos through my Mesa Mark IV and the DiMarzios through my Rivera TBR-1SL. I'm getting horrible buzzing through the Rivera (which is overdriven). However, once I unplug the guitar from the Rivera, the buzz is gone. I can basically use the guitar with either the Mesa OR the Rivera without any issues, but the moment that I use two different amps, there's nothing but buzzing. I've tried this with several different amp combonations, and 3 different EB/MM JPM's and have had the same issue with all setups. I've tried every possible combonation of the ground lift switches on the two amps, and there is not change regardless of what I do.

Any suggestions at remedying this issue?

Thanks ahead of time,
Chris

Gresh · #5 07-26-2002, 01:47 PM

Is it just the piezo signal that is buzzing in all combinations? Does the EB piezo out use a separate jack or a stereo plug? Have you changed out cables? Does the piezo out still buzz when only using it with the Rivera...ie...you don't have the magnetic output utilized at all? All in all, I would try doing just one thing at a time to isolate where buzzing occurs and where it does not.

I would do that (you probably already have). Once you find out the item addition that introduces buzz then you've got it narrowed down. If you get piezo buzz running stereo to the TBR, but don't get it when just mono piezo and it's not a ground loop issue then I would suspect you have a wiring issue in your EB. But who knows.

vaijem777 · #6 07-26-2002, 01:56 PM

Hey!

The EB/MM JPM has dual outputs: (1) for the magnetic pickups only, (1) for that works for either the piezos alone, or for both sets of pickups if used in mono. The buzzing only occurs with the magnetic pickups, and it occurs only if I am using any combonation of two amps. I can run either/both sets of pickups through the Mesa or the Rivera mono (or singularly) and I have no issues at all. I have tried a stereo "Y" cable as well, utilizing only the "Mono/piezo" jack, and still have the same buzzing. The piezo is always silent, but the DiMarzio's are where the buzzing occurs (either through the Rivera or the Mesa). I've tried several sets of cables, and 3 different EB/MM JPM's, all with the same results. I'm baffled! Basically, it sounds like I'm having the exact same issue as Drew is, but the groundlift changes are having zero effect. For the record, I have been having the same issue when running the piezo directly into the PA as well.

Two hands31 · #7 07-26-2002, 02:34 PM

Could be a shielding issue between the two jacks, depending on how close they are to each other. I'm just guessing though. Since you can use one jack or the other with no problem, but when you use both it causes problems.

Rich · #8 07-26-2002, 02:37 PM

In my vast experience with electronics I can conclude one thing, a call to EBMM couldn't hurt

Gresh · #9 07-26-2002, 03:12 PM

Quote:

Originally Posted by Rich

In my vast experience with electronics I can conclude one thing, a call to EBMM couldn't hurt

My sentiments exactly! Sorry if I confused the issue, I thought your issue was with the piezo output. Two Hands, he's having the same issue when using the summed output for both signals so it can't be an issue with piezo output jack alone.

Two hands31 · #10 07-26-2002, 03:14 PM

:doh: Ignore me.