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Signs of Failure in a Fishman Full Circle Pickup

Discussion in 'Amps, Mics & Pickups [DB]' started by jmlee, Jul 25, 2017.


  1. jmlee

    jmlee Catgut? Not funny. Supporting Member

    Jun 16, 2005
    Halifax, Nova Scotia
    I'm currently on my third Fishman Full Circle pickup.

    (i) The first one died when some kittens we were fostering chewed through the cable near the adjuster. Meow. No Mix.

    (ii) The second one failed outright—but in the couple of weeks before it did, the pickup became enormously more feedback sensitive, to the point where it was nearly unmanageable in any sort of loudish performance.

    (iii) Here's where it gets good. My latest Full Circle has suddenly done the same thing: becoming very feedback prone where it wasn't hardly at all beforehand. No other change in gear. It's still working, but it's a pain.

    Has anyone else experienced this phenomenon?
     
  2. Chris Fitzgerald

    Chris Fitzgerald Student of Life Staff Member Administrator Gold Supporting Member

    Oct 19, 2000
    Louisville, KY
    I'm also on my third Full Circle, but have never experienced the feedback phenomenon. The first one gradually got quieter, then would would occasionally send out a distorted signal on really loud pulls on a certain string - the distortion was my clue. The second one just got the distortion. My understanding of what fails in these pickups is that one of the Piezoelectric crystal inside the pickup cracks and loses efficiency. I'm sure someone who understands the mechanics better than I do can chime in with better information; I would be interested to hear how the failure mechanism could lead to feedback.

    A couple of questions:
    - Have you noticed the pickup losing signal so that you need to turn the amp up much louder to get a usable signal?
    - Have you tried turning the pickup so that the wire is oriented differently against the bridge feet corners? Does turning it change anything?
    - Where is your bass in relation to your amp when this happens?
     
  3. Distortion generates or enhances mostly higher frequencies. You get a higher output on these as before and there feedback starts, because it generates a resonance on these frequencies.
    Try to play a double bass with a fuzz effect and you get a lot of feedback. Guitarists who use distortions effects generally need a compressor/limiter to avoid using amp and speaker to limit the output on a high level.
     
  4. jmlee

    jmlee Catgut? Not funny. Supporting Member

    Jun 16, 2005
    Halifax, Nova Scotia
    - Yup, I think there is a loss of gain occurring. It's a bit hard to tease out of my set-up since i have an HPF2 on the bass, a SansAmp Para-Driver DI, and then my Acoustic Image head: each with one or more gain settings. Certainly, the loss of signal would cause me to increase the front-end gain and perhaps encourage the feedback problem.
    - Tried a 45° rotation on the pickup. No effect other than the change in character of the sound.
    - I haven't had any small ensemble work since the problem began, so just big band rehearsals and two gigs. At most of those, the amp and I are in the same positioning, with it about 5 feet behind me and off to one side. I use the phase switch on the HPF and the low pass filter there (or at the AI head) to get best feedback suppression. I had the same problem at the local Jazz Festival ten days ago with their backline in a different position.

    All said, I think it's the creeping gain loss that's the issue—matching your experience, Chris. I've not noticed the distortion effect though.
     
  5. Chris Fitzgerald

    Chris Fitzgerald Student of Life Staff Member Administrator Gold Supporting Member

    Oct 19, 2000
    Louisville, KY
    If you have multiple gain stages, you may also be experiencing a gain stage issue. Before I used my current setup that allows me to set the input gain, I often ran into a similar problem. The best solution I came up with was to either max out the master gain (or set it at 3 o'clock on the dial if you aren't comfortable with diming it) and then set the first gain stage to where you are getting a good sound with no distortion of feedback. I would try plugging into just the AI head and working outward from there. If the feedback is coming from just the AI head, then it may be a pickup problem; if not, then you may be dealing with a gain-staging issue. I have found multiple gain stages to be very sensitive and don't like dealing with them, to the point that if I am using a different preamp in front of an amp that already has two stages (like the AI) I'll bypass the first one and plug the preamp directly into the effects return.

    You may already know all of this stuff, but I thought I'd post in anyway just in case, and also for anyone lurking in this thread who may be having a similar issue. Good luck!
     
  6. lurk

    lurk

    Dec 2, 2009
    I've had 2 fail. I'm now on my first lifeline; can't decide if I like it more or less than the fc. Both of my FCS died the same way: intermittent cutting out that at first I thought might be my imagination it was so short. Gradually got worse and very obvious.
     
  7. james condino

    james condino Spruce dork Supporting Member Commercial User

    Sep 30, 2007
    asheville, nc
    The day you after pay for it, the full circle seems to hit the half life and they go downhill from there.
    It is a shame the durability is not equal to the sound you get out of a full circle. The irony is that the old BP100 sounded terrible but it held together for decades.....
     
    Don Kasper likes this.
  8. Chris Fitzgerald

    Chris Fitzgerald Student of Life Staff Member Administrator Gold Supporting Member

    Oct 19, 2000
    Louisville, KY
    To be fair to the FC, mine have each lasted about 7 years, which for me seems reasonable given the tension I keep them under and the amount of carefree playing I get out of them. The Realist I had at the beginning only lasted a few years before it started crapping out, and I really haven't found another pickup I like even half as much, so...
     
    jazzykitty likes this.
  9. Jon Mush

    Jon Mush

    Jun 3, 2015
    Winnipeg, MB
    Mine got quieter as well and distorted. When I got my new one I noticed a lot more high end when I replaced it. Same bass, same strings.

    If you are looking at another FC, remember that Fishman has a repair service. They charged me $50 and gave me a brand new one as it was deemed unrepairable.
     
    Chris Fitzgerald likes this.
  10. jmlee

    jmlee Catgut? Not funny. Supporting Member

    Jun 16, 2005
    Halifax, Nova Scotia
    Thanks, I am aware of all that and manage it pretty well. [I actually teach feedback systems in my day job...] I'm so obsessive about settings that, when I find a set which are near-perfect, I photograph them and have them on my cell for reference. What I was thinking was that I've been perhaps gradually creeping upward on the volume setting on the HPF right at my bass—and applying more filtration there as well.

    I did go back and look, and it's been nearly 5 years and a lot of playing since I last replaced the Full Circle. Perhaps that's not so bad. My suspicion is that the strain/vibration sensors inside the adjuster gradually delaminate, to the point where signal level degrades and the remaining adherent sensor can be overloaded with a hard pull. It probably takes time for a fatigue crack to develop and then propagate.

    The problem with sending the transducer back to Fisher for service is that, being in the bridge adjuster, I'd be without my upright until I got it back. Time to just suck it up and buy another one I guess.
     
    Chris Fitzgerald likes this.
  11. Jon Mush

    Jon Mush

    Jun 3, 2015
    Winnipeg, MB
    Yeah, I have a few spare adjusters lying around. They're probably cheaper to buy than another pickup, though.
     
  12. Kai Sanchez

    Kai Sanchez Supporting Member

    Sep 12, 2006
    Miami
    You can call Fishman's tech support and order a pair of adjusters. Ask for the dummy adjusters of the full circle pickup.
     
    Last edited: Jul 26, 2017
    Jefenator likes this.
  13. Weird! I've been using the same Full Circle, without issue, since they first came out (10 years ago?). It has been on at least 2 basses, has been giggled hundreds of times and has been totally trouble free. Lucky me, I guess.
     
  14. Ric Vice

    Ric Vice Supporting Member

    Jul 2, 2005
    Olivette, Missouri
    I think that old adage "results may varry" applies. Apparently there is more pressure exerted on the piezo crystals inside the full circle. Different bridges and tailpieces exert more pressure on the pickup elements. The same is true for the "Realist" Copper foil. The average being around
    4 years.
     
  15. bdowd

    bdowd Supporting Member

    Oct 27, 2005
    New Hampton, NH
    My most recent full circle has lasted 10 years, same bass, various strings, but is currently dying! Loss of volume, distortion when I dig in. Will Fishman really try to repair it if I send it in? How many of you guys have had that work out for you?
     
  16. Ric Vice

    Ric Vice Supporting Member

    Jul 2, 2005
    Olivette, Missouri
    Something was mentioned about that in the old Full Circle thread. I know you can replace Fishman's 1/4" jack assembly.

    Ric
     
  17. Jon Mush

    Jon Mush

    Jun 3, 2015
    Winnipeg, MB
    I did it about a year ago. You pay shipping,$50 max on repairs. They'll repair or replace (if over $50). Was painless and cheaper for me. The most you're out of pocket is shipped + $50.
     
    jazzykitty and Chris Fitzgerald like this.
  18. jmlee

    jmlee Catgut? Not funny. Supporting Member

    Jun 16, 2005
    Halifax, Nova Scotia
    Well, looks like the Full Circles have a finite lifetime: maybe 5-10 years. That's kind of disappointing given that they're not (at least in my case) subject to much abuse other than the vibration of a lot of playing.
     
  19. Ric Vice

    Ric Vice Supporting Member

    Jul 2, 2005
    Olivette, Missouri
    I'm not certian that vibrating the piezo crystals is what eventually causes them to degrade. From what I've read, it's the pressure exerted on the piezo elements by the bridge, that causes them to fatigue. Unfortunately, they aren't as robust as a microphone, but they're much

    less hassle to use and mount. Just my take of course. They haven't been sucessful at creating a everlasting gobstopper pickup.

    Ric
     
  20. jmlee

    jmlee Catgut? Not funny. Supporting Member

    Jun 16, 2005
    Halifax, Nova Scotia
    I'm thinking fatigue failure of the adhesive holding the sensors onto their substrate. I doubt they're directly compressed themselves, more likely the aluminum casing. Personally, I don't know that the sensors are piezoelectric, ferroelectric, strain gauges or what.
     

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