Need Help Fast!!!

bhenson · #1 08-09-2009, 11:56 AM

I Need Help!!! I have a Jacob Erich (carved top) bass that recently had some upgrades to it. I had been using the Fishman BP 100 and wanted to upgrade to the Full Circle (note: I had the Full Circle installed threads up and I use the Pro EQ Platinum). While it was in the shop, I decided to upgrade the end pin, the tail piece wire and a new bridge. After all was done, the bass sounds great acoustically. However, when it is amplified, all sorts of feedback occur. It mainly centers around the frequencies ranging from Ab-C. When playing these notes, the pitch is muddy and feedback develops. Upon further investigation, I have learned that the bridge is vibrating and providing extra tones and the pickup is taking off with them. If I use my forefinger and thumb to clamp down on the bridge, it goes away and all the notes are clear.
I used this luthier to fix a crack and thought highly of his work. He was close and reasonable, so I used him for all the upgrades. There are two things I have notice about the bridge work that seem suspect. First, the top does not taper down toward the strings. He left it at full thickness after shaping it. Second, the notches for the strings are very shallow. Should I go ahead and have him fix the bridge to where I think it should be, or is what I described not that big of a deal?
Does anyone have suggestions? Please?!? I am desperate and need this bass functioning NOW!
Thank you,
-b

salcott · #2 08-09-2009, 12:22 PM

Paradoxically, the better acoustic sound your bass has, the more difficult it will be to amplify. If doing the thing with your thumb and finger works, try using the mounting clamps from the BP 100 or a little C clamp to perform the same function and take them off when not needed.
The notches in the bridge should be no more than 1/2 the diameter of the string; if the string doesn't pop out when you play, there's no problem. As far as the taper, I think it's individual to each instrument; you could just ask. In my experience, most luthiers are happy to educate their clients.

bhenson · #3 08-09-2009, 01:02 PM

Thanks for the reply! I have tried all sorts of clamps (including the BP 100 clamps) and it does not work. I just now took the bridge off and was inspecting the installation of the adjusters. It looks like the hole in the E leg (the side the pickup is on) is fairly off center. I wonder if this would make the difference.

jallenbass · #4 08-09-2009, 01:14 PM

Quote:

Originally Posted by bhenson

the notches for the strings are very shallow.

That seems right to me. The notches should only be as deep as needed to keep the string in place.

CPike · #5 08-09-2009, 04:36 PM

Post some pics if you can...

Quote:

Originally Posted by bhenson

I just now took the bridge off and was inspecting the installation of the adjusters. It looks like the hole in the E leg (the side the pickup is on) is fairly off center. I wonder if this would make the difference.

Turnaround · #6 03-15-2012, 06:08 PM

I just did a Full Circle installation and though the Fishman is supposed to be very good at feedback rejection, this one just howls. I am pretty sure that it is doing so because the output level is diminished and consequently the amp volume is being turned up - thus introducing feedback.

The disk is sitting nice and flat against the foot (threads up in this case) but I have a suspicion that the unthreaded section is binding a bit in the foot when the whole thing is under string tension. That tension does change the geometry of the top and may cause a slight angling of the foot, causing the post to bind a bit.

The simple solution here is to increase the diameter of the hole in the foot a bit. I'm going to have a go at this tomorrow and will post the results. Meantime, anyone else have a remedy?

Heifetzbass · #7 03-16-2012, 04:03 AM

Does this luthier do a lot of bass work, or primarily vln, vla, and cello?

If you can afford to work with the luthier and let them try to fix it, hopefully for no cost, I would. Is this the first full circle they installed? Sometimes luthiers need to be educated on this stuff too. They might be able to consult with some more experienced luthiers on the PU installation and work everything out for you.

I would give them the chance to "make it right".

BG

Greg Clinkingbeard · #8 03-16-2012, 07:11 AM

I installed one that behaved like that. Although it initially looked like it was making complete contact with the bridge, upon closer inspection there was a small gap. The contact should be perfect, both from top to bridge foot and bridge to pickup.

arnoldschnitzer · #9 03-16-2012, 07:18 AM

Wind a piece of foam or cloth through the string afterlengths, to turn off the vibrations occurring there. I suspect that now that everything is vibrating effectively, the afterlengths are also, especially when you play certain notes. The pickup does not "know" it's not supposed to amplify those sounds.

robobass · #10 03-16-2012, 01:25 PM

Are you sure that the input impedence on the amp is well matched? A mismatch could be the problem. Try it with a different rig/good preamp and see if the problem persists.

fdeck · #11 03-16-2012, 06:35 PM

Do you have a wolf eliminator? I had one that helped with my acoustic tone but caused a sort of howling thump when playing through my Full Circle, with or without hi-z preamp.

GrowlerBox · #12 03-16-2012, 08:24 PM

Beware the zombie thread. I'm hoping the OP's problem was addressed at some point during the past 2 1/2 years.

fdeck · #13 03-16-2012, 10:15 PM

LOL, oops.

petesenkowski · #14 03-17-2012, 04:19 PM

Quote:

Originally Posted by GrowlerBox

Beware the zombie thread. I'm hoping the OP's problem was addressed at some point during the past 2 1/2 years.

True, but Turnaround experienced a similar problem and resurrected the thread to get help.

Turnaround · #15 03-19-2012, 08:36 PM

Quote:

Originally Posted by petesenkowski

True, but Turnaround experienced a similar problem and resurrected the thread to get help.

Interesting - I didn't realize I was ressurecting an old thread. I thought I was responding with additional questions to something current. Don't know how that wierdity happened.

In any case, I think the problem is solved - maybe. The problem occurred because I had to fit new feet to an existing bridge that was already equipped with Full Circle pickup. Installing bridge adjusters on a bridge that's in one piece is an exacting job, but doing it backwards courts disaster. How the heck can you line up the foot to the table and the predrilled hole in the bridge leg?

Well it can be done, though I don't recommend it. I cut new feet slightly too high and angled as close as possible to the leg of the bridge. I taped the feet to the bridge with the FC out of the equation. Then I proceeded to fit the feet to the table as best I could. Then I had to drill the new feet at the proper location and angle to match the legs. I used some lipstick on the end of the leg and pressed it up against the foot so I could see where the hole needed to be. They weren't centered on the leg properly, each leg was different, and one leg was almost 1/8" longer than the other. At this point I should have thrown in the towel and said it's time for a new bridge.

But because the player needed the bass right away, I persisted. I made a clamp to hold the bridge and lined up the bridge in the clamp on my drill press using a close-fitting drill into the hole of the leg. Now I hope I can describe this... the bridge in the clamp sat on top of a block of wood that sat on the drill press table. The block was high enough that it could accomodate the inverted bridge and allow me to find the drilling angle by running the bit into the leg hole. Once that was lined up used my drill press vice to clamp a foot while it was lined up and flush with the leg in the other clamp. That is, the drill press vice was resting with it's upper edge flush with the top of the bridge clamp, and the foot was flush with the leg of the bridge. That way I had established the correct angle for the hole in the foot. Drilled the hole and repeated for the other foot.

All seemed to be OK, but as I stated, the result was feeding back and had poor output levels otherwise.

On revisiting the problem, I discovered that as careful as I had been, the post was not aligning with the hole in the foot very well. And consequently the post-to-hole angle was preventing the foot from seating with the table properly and making uneven contact with the Full Circle. I have subsequently enlarged the holes in the foot (I should mention that the installation was with the threads up), to eliminate binding and recut the top of the feet to better contact the adjusters/pickup. Seemed OK in my shop. The owner hasn't got back to me yet, so his experience may differ from mine. But I'm pretty sure I would have heard from him immediately if the problem was not corrected.

So, at the risk of preaching to the converted, I will say that I do not recommend trying to install new feet on an existing bridge that has adjusters. It is simpler, more reliable and cheaper to replace the bridge entirely and install the adjusters/pickup the conventional way. Your results may vary, but I doubt your frustration level will be significantly different.

FWIW.

Turnaround · #16 03-19-2012, 08:47 PM

Quote:

Originally Posted by arnoldschnitzer

Wind a piece of foam or cloth through the string afterlengths, to turn off the vibrations occurring there. I suspect that now that everything is vibrating effectively, the afterlengths are also, especially when you play certain notes. The pickup does not "know" it's not supposed to amplify those sounds.

Thanks Arnold. I will look into this a bit. The owner of the instrument said it was playing fine, amplified and not, until I did the bridge work. There's a lot to this story, but in short the owner bought this bass from a light touch jazz player, but he is a rockabilly whacker. He installed his fave gut strings and cranked the bridge up HIGH. There couldn't have been a quarter inch of thread inside the bridge leg. We "discussed without agreement" (argued) a bit and I agreed (foolishly) to replace the feet on the bridge with higher ones. You'll get a fuller picture from my previous post. It just goes from bad to worse. I've been at this for decades but I have a soft spot for those poor working musicians that can barely eke out an existence. And you know, I don't really complain about this. I've done OK. And this is how I repay.

Greg Clinkingbeard · #17 03-19-2012, 09:00 PM

Couldn't you have glued some maple to the top of the old feet and drilled up through the bottom?

Turnaround · #18 03-19-2012, 09:23 PM

Quote:

Originally Posted by Greg Clinkingbeard

Couldn't you have glued some maple to the top of the old feet and drilled up through the bottom?

That was my first option with the owner. I know him well enough to know that his objection to this approach would be that it was unsatisfactory, even if it worked well. I won't go into the whole story here. I just wanted to share my experiece with anyone that finds themself in a similar situation - i.e. not a good approach if it can be avoided.