Fishman Blender Hum (ground problem?)

[Robby]

So I'm plugging in for praise band practice last night, and suddenly, there is a distinct hum/buzz coming through the PA and the Aviom units from my guitar channel. This is from my 2002 714ce through a Morley A/B/Y -- Boss TU-2 -- Yamaha AG Stomp and into the board back in the sound booth. To date, I have never had a problem with this guitar, in that noise from the electronics is usually almost non-existent in this setting.

After trying all sorts of different cables, batteries, and bypasses to no avail, it seems that it's some sort of ground problem (at least to me it does). If I merely touch the endpin jack with my finger or the AG Stomp with my foot, the hum disappears. We also plugged in two other guitars in this same setting without a hum, so we know it's related to my Taylor.

I even tried isolating myself from the system by plugging into my Sennheiser EW172G2 wireless unit, but the noise was still there. However, if I merely touched the G2 sending unit, the noise went away.

I can slide the blender over to 100% mic and the noise is gone, but this may be a function of the decreased eq impact from the internal mic. Or it may be related to the UST. I saw a couple of threads mentioning the UST issue, but it seems odd that an off-placement of the transducer in the slot would create that much hum, especially since I've not replaced the saddle.

Has anyone had this issue with the Fishman Blender? I know zero about guitar electronics and the circuitry involved in the blender unit, so if you say the words solder, voltmeter, milliamps, or ohms, you're over my head before you even finish the sentence.

Any info is greatly appreciated.

-Rob

[ljguitar]

Originally Posted by Robby

...Any info is greatly appreciated.

Hi Rob...
It could be a detached ground wire in your rig, or perhaps some other piece of gear in the church's system has been added, removed, changed or rewired.

Try plugging into a DI box with a ground lift and see if it goes away.

[Robby]

It's not in the system, because the several other guitars we tried on the same line were all silent. I tried 3 different DI boxes and flipped the lift on each of them. I even bypassed the DI setup and went straight out of the AG Stomp using the TRS/XLR convert cable included. Same result.

It has to be something in the internal pickup system. We played an outdoor Fall Festival last Sat, so I wonder if I knocked something loose in the electronics in all the load in/out.

[guitaniac]

Rob,

I had the same kind of problem with a Prefix Plus-equipped Wechter which I bought off ebay. It had a ground hum which would disappear when I touched the guitar cable plug (as ground hums always seem to react). In the Wechter's case, it turned out to be that some of the UST's shielding had been scraped off. I actually had to replace the UST to fix the hum. I hope that its an easier-to-fix problem in your case, but it may not be. Over the years, I've had to replace three USTs which had gone bad and were causing unacceptably noticeable hum problems.

Gary

[Brackett Instruments]

From Fishmans web site
http://www.fishman.com/support/techtips.asp?id=22

Joe's Tech Tips
My Acoustic Matrix pickup is balanced and sounds great, but I’m noticing a hum that sometimes disappears. I can make the hum disappear when I touch the endpin jack. Is this an electronic problem?

A humming pickup is almost never the result of an electronic problem, but rather the result of issues surrounding the installation of the pickup in the saddle slot. The most obvious reason to look for is a tear or rip in the foil wrap of the pickup. This material is the shield of the pickup and when disturbed will cause the pickup to hum. Another reason for hum is a poor fit of the pickup or saddle in the saddle slot. The Acoustic Matrix pickups ground properly when under correct pressure in the saddle slot. Anything than may impede the pickup from being properly compressed in the slot, can be a cause for hum. You should be sure that the pickup drops easily into the saddle slot. It should not be forced in to a tight slot. Also, be sure that the saddle slides easily into the slot while not being too loose. Because the bridge is made of wood, it will expand and contract with regard to humidity levels and temperatures. This movement can affect the pickup and saddle fit, which can result in the hum being intermittent. While this is the most difficult type of hum to correct, with a proper fit of pickup and saddle, it should be a rare occurrence.

[Robby]

Gary & Woody:

That is some really good info. I'll pull the saddle this weekend to see how the UST is sitting and if there's any shielding damage.

Plus, it will give me a reason to finally install that FWI saddle I bought from Colosi about a year ago....

Thanks again -- I appreciate both of you sharing your knowledge and experience on this. I'll let you know what happens.

[Hose64]

Hi Rob, I have just had the same problem with hum noise and the culprit was the Fishman Prefix Pro UST. Some of the covering had eroded and was causing the problem. So I had the idea of covering it with a thin carefully cut strip of aluminium foil. Neatly placed I then replaced the saddle and the strings and with fingers crossed plugged my guitar in. Not a whisper... no noise at all!! The guitar sounded great through the amp. I count myself lucky as I was expecting an expensive repair. I hope this is of help to you or anyone with the same problem. Regards, John M.

[zematynnad]

I'm going to try this as for the first time in 20 years I'm noticing a persistent hum from the pickup. Thanks for the info! I've got the stereo prefix blender on a 2001 714CE and I absolutely love the way it sounds.

[zematynnad]

Tried re-seating the pickup element - didn't change anything. Tried the aluminum foil thing - didn't fix it either. Still getting hum.

So I ordered a new UST and put it in. No hum, all is great again! Oddly though I could not see anywhere in the shielding around the old pickup element where there was a rip or tear - looked fine to me.

[Jimbo48]

I had the exact same issue with my 2002 Taylor 614 with the barn door Fishman system. From advice on the Forum, I pulled and reset the saddle - worked fine. Next time - worked fine. Third time - nope. Emails with Fishman customer service revealed the UST worn shielding problem - please purchase a replacement UST.