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Old 10-13-2014, 10:26 AM   #1
Guijs
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Join Date: May 2014
Fishman onboard preamp, no sound on higher E string

Hello,

I have a Gibson EC30 BKE equipped with Fishman Prefix Plus onboard preamp.

I haven't plugged it on an amplifier for several years, and today I realized that I have no output sound on higher E string.

I already tried removing the saddle to check the undersaddle pickup position and it seems that the pressure is even over the pickup, and the position is correct. The output on all the other 5 strings (E-A-D-G-B) are ok and sound even.

Is this a common problem with undersaddle pickups? Should I look for a replacement or do guys know another kind of test that I should do to resolve this?
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Old 10-13-2014, 10:44 AM   #2
Garthman
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Join Date: Dec 2013
Inequality of sound across the strings is usually due to poor contact between the UST and the base of the saddle. On a "bar" type UST with individual piezo crystals (these are visible as raised sections under the plastic covering) it could be caused by a duff crystal but this is rare.

Best way to test it is to remove the saddle - leave the UST in the slot - and connect to an amp. With the blade of a small scewdriver, gently tap the UST on each crystal (or along it's length if it's the co-axial type) and see if you get a sound from the amp. If you don't get a sound you have a faulty UST (which can usually be replaced), if you do it's a contact problem.

If it's a contact problem you will either need to sand flat the base of the existing saddle (you can use a shim to compensate for the loss of height if nec), or you could fit a new saddle or (and this is an excellent remedy) you can place a thin shim of self-hardening clay between the UST and saddle base. I always do this when I fit a UST - it enables a perfect contact, it's cheap and easy to do and it's completely reversible.

If you want more info, PM me your email address and I'll send you some instructions.
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Old 10-13-2014, 05:45 PM   #3
Tony Done
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Join Date: Apr 2014
Quote:
Originally Posted by Garthman
Inequality of sound across the strings is usually due to poor contact between the UST and the base of the saddle. On a "bar" type UST with individual piezo crystals (these are visible as raised sections under the plastic covering) it could be caused by a duff crystal but this is rare.

Best way to test it is to remove the saddle - leave the UST in the slot - and connect to an amp. With the blade of a small scewdriver, gently tap the UST on each crystal (or along it's length if it's the co-axial type) and see if you get a sound from the amp. If you don't get a sound you have a faulty UST (which can usually be replaced), if you do it's a contact problem.

If it's a contact problem you will either need to sand flat the base of the existing saddle (you can use a shim to compensate for the loss of height if nec), or you could fit a new saddle or (and this is an excellent remedy) you can place a thin shim of self-hardening clay between the UST and saddle base. I always do this when I fit a UST - it enables a perfect contact, it's cheap and easy to do and it's completely reversible.

If you want more info, PM me your email address and I'll send you some instructions.


I agree with all of that.

Just a couple of additional comments:

If is is completely dead, I'm betting on a dud piezo element under the offending string - the tap test should catch that.

If it is poor contact, it might be the bottom of the saddle slot that is at fault. Shims under individual strings can fix that, but it can take a lot juggling to get the balance right. I got so desperate on one that I made a jig, using medieval technology, to level the bottom of the fret slot. It still needed shims, but it was a lot easier. Pics availble if you are interested.

Another balancing option is to cut vertical keyhole slots in the bottom of the saddle to give it some flexibility, Fishman were selling one for a while, I think it was called the Fishbone. I've made these, and it works well in some circumstances.
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