The Last Bass Outpost

Hi guys, Thunderbucker here.  The usual reason an electric bass or guitar feeds back is due to the pickups, not the wood (an acoustic instrument can feedback due to the sound board being moved by the amp sound, just as the string motion would)

Pickup feedback is caused by something in the magnetic field of the pickup being able to move. Remember that the pickup works because the iron string is moving in a magnetic field, and that there is a coil of wire that senses the changing magnetic field.  And either changing the magnetic field, or moving a coil in it (the principal that a generator uses to make voltage and current) can cause an output.

So if anything magnetic can be moved by the amp sound (this can be the metal pickup can, nickel silver is slightly magnetic), or if any of the coils can move, then the pickup can become microphonic, that is, behave like a microphone. and of course, mics can feedback.

The most common cause is the potting (or lack thereof) of the coils.  Usually, the coils are wax potted (dipped in molten wax for 15-30 minutes, sometimes with a vacuum pulled to help get the wax into all the crevices).  You can see this in the Seymour Duncan you tube tour.  This is time consuming and messy, so companies often try to cut corners on this.  When CBS bought Fender, it was one of the first processes they cut, as a result, post CBS guitars fedback badly unitil they realized they had to bring back the potting process.  I had a CBS tele with this problem. Sounded great, squealed like a pig.

You can test pickups for microphonics by tapping lightly on the pickup with something non-magnetic (don't use a screwdriver!).  A wooden rod would be ideal (don't hit the strings, hold them very still).  Even with a well potted pickup, you will still hear some of the tapping come out of the amp.  But this test will clearly distinguish a very microphonic pickup from a much quieter one.

Thanks, guys.  Mike got his bass yesterday, so far he's digging it and raving about the sound...sometimes I think I'm only making a platform for Steve's pickups

And I thought I was only making pickups to go in your basses.  Hmmmm

Yes it sounds as if your Lull pickup has an internal connection between the black wire and the can, meaning that you can't reverse the phase connections without leaving the can connected to the pickup hot output.  That would cause all kinds of buzzing when you touch it.  Confirm this with the ohm meter, that one of the output wires is in fact permanently connected to the case of the pickup.  If that is so, then the pickup must be connected so that the case side is ground. 

And the other pickup must be phase reversed so that it sounds good.

PLS DO NOT DESTROY.  it is too easy to make a pattern.  Buy some contact paper, cut to rough size of the "flattened" part.  Stick to to your t-shirt couple of times to weaken the stick.  carefully wrap it onto the hand rest.  trim off excess with exacto, including the holes.  Ustick the pattern from the part, and stick onto stiff paper. Measure and add dimensions.

Now view the hand rest from the side, and measure the height, and width of the raised area. To estimate the bend radius, use a compass to make a series of small circles out of stiff paper, 1/8", 3/16" etc.  Cut out and compare to the bend radius on the part.  Incrementally zero in on the correct radius (of course, a set of radius gauges would be simpler)

There Ya Go.  Fully dimensioned drawing, and Mother is Still in One Piece.

Shipped today, 2 sets of 66 ThunderBuckers to addresses in Australia and a 63 bridge to Illinois! ThunderBuckers around the world!

My buddy Carlo sent me a Squire J neck to replace the cheap P bass neck on TestBass (the bass I cycle all the pickups I make through to test them out). That P bass neck plays like a splintery 2X4, except maybe not as good.

I was looking forward to a nicer neck, except the neck Carlo sent had a pronounced ski-slope about 5 frets from the nut.  Even tightening the truss rod to near infinity would barely take it out, and that was with no string tension.

So I remembered a trick I saw at Charvel's in Azusa in the late 70's, when it was in back of the strip club.  They had a jig where you could clamp a bowed neck straight, then put a heat lamp on it.  Kind of like steaming wood so that you can bend it.

I clamped my bowed neck to the workbench, with a shim so that I could actually reverse-bend it a little, and put a heat lamp on it (a chicken incubator, to be more exact).  I watched the temp with my IR temp sensor gun (don't want to set no fires or bubble no finish) and held it at about 190F for about 30 minutes.  Then I turned the heat off and let the neck cool in the clamped condition.



I took it out of the clamps, and wow, it was really straight!  Hard to take a picture of though...



Now it is ready to make its acquaintance with Mr TestBass.