Neck Pickup Attack

[bea]

Hi there,

may i ask another question regarding mostly (but not only) mudbucker clones?

The attack of my Epiphone EB-3 depends *hugely* on the chosen pickup: with the neck PU it is really fast and responsive, with teh neck sidewinder it is, however, slow. Slower tan i would like to. The PU in question is a modded sidewinder used by Epiphone: two additional Alnico magnets and a steel bar between the bobbins. Its resonance frequency is surprisingly high - 3.1 kHz under a load of 560 pF.

In direct comparison, the attack of Gibson's recent pseudo sidewinder is a lot faster (otherwise, the sidewinder would be the better PU).

I would like to understand what's going on - eddie currents? Where? In the steel blade connecting the bobbins? In the additional steel around the pole pieces?

(And of course i'd like to learn about curing the effect)

[Mike Sulzer]

Hi Bea,

The width of the resonance might matter, too. Does one have a higher Q than the other?

[bea]

I did not measure the Q, just determined the resonance from a Lissajous figure. But the Q of the sidewinder seems to be pretty large - without additional damping the resonance is pretty sharp, and it can output sharp peaks of about 4 V (!!). I actually varied the damping a bit, but that will not change the effect in general.

[Mike Sulzer]

I did not measure the Q, just determined the resonance from a Lissajous figure. But the Q of the sidewinder seems to be pretty large - without additional damping the resonance is pretty sharp, and it can output sharp peaks of about 4 V (!!). I actually varied the damping a bit, but that will not change the effect in general.

Maybe the thing to do is to try and find out if the sound you do not like is inherent or involves interaction with the external circuit. Suppose you play with a very short cable, or use a preamp with a very short cable from the instrument, thus reducing the capacitance quite a bit?

[bea]

The load capacitance is definitely not the cause. The instrument (btw meanwhile active) has a C-switch. To some degree it seems to be a property of these basses - i played three of them and already thought of replacing the fingerboard. But anyway, i am pretty sure that there is some influence of the pickup.

[David King]

Hi Beate,

What strings are you using? It's a 31" scale or something longer? So many factors fighting you here. ;-)

[bea]

The Gibson is 30", the EPi 30.75. They use different strings. Despite of that i know the Epi wuite well and have an clear impression of what comes from the strings, what from the instrument (neck stiffness) and what form the pickups.

The sidewinder is a modified one with an additional steel blade in the center and a pair of alnico magnets in addition to the stock ceramic magnets.
In the last days i applied a minor change to the sidewinde which produced a fairly large effect: i interchanged the magnets. Put the ceramics from the top to the bottom and the (weaker) alnicos to the top. Effect: the tone is lightened up a lot and the tone comes up a bit "faster" - even if i pull the resonance down.

[David Schwab]

The Epi mudbucker is wound with what looks like 36 gauge wire. I have been either rewinding these for people with 40 gauge wire, or replacing it with my own sidewinder.


The Gibson SG bass is a humbucker masquerading as a sidewinder. It has an aluminum bar on the top with fake pole screws. They use mini humbucker bobbins and ceramic magnets. For what ever reason they put the blades in the bobbins up side down, so they never get very close to the chrome cover. It's not a very well designed pickup.

[salvarsan]

The Gibson SG bass is a humbucker masquerading as a sidewinder. It has an aluminum bar on the top with fake pole screws.

If you replaced the aluminum bar with a non-metal, eddy currents would decrease and the high frequency response might improve. I wonder if there would be a worthwhile audible difference.

[Mike Sulzer]

If you replaced the aluminum bar with a non-metal, eddy currents would decrease and the high frequency response might improve. I wonder if there would be a worthwhile audible difference.

That does look like a lot of aluminum. if the pole screws are steel, could they have some role in guiding flux through the coil?

[salvarsan]

It's a blade humbucker with extra space between the coils. I suspect the screws are not merely ornamental but serve to soak magnetic flux away from the strings.

The blades are not in contact with the cover but are electrically connected by the aluminum block. Somebody with better insight could discuss the differences between the magnetic circuit and the eddy current circuit.

FEMM magnetic modeling software is now available as a 64bit executable so I think I know what I may do until the foot of snow gets scraped off the backroads.

[Mike Sulzer]

It's a blade humbucker with extra space between the coils. I suspect the screws are not merely ornamental but serve to soak magnetic flux away from the strings.

The blades are not in contact with the cover but are electrically connected by the aluminum block. Somebody with better insight could discuss the differences between the magnetic circuit and the eddy current circuit.

FEMM magnetic modeling software is now available as a 64bit executable so I think I know what I may do until the foot of snow gets scraped off the backroads.

So the screws really are located between the coils? That is derision worthy.

[salvarsan]

So the screws really are located between the coils? That is derision worthy.

Lookit dah pikchah.

Yes, a fool designed that pickup, someone who thinks bass players are idiots (and who never heard of Scott Ambush or Victor Wooten).

BTW, the 64bit FEMM won't run under Wine on Linux, so I'm sticking with the win32 release.

[bea]

...never get very close to the chrome cover. It's not a very well designed pickup....]

I agree, i knew when i bought that bass. I got it for a reduced price - cheap enough to justify new pickups. The pickup maker closest to me has got an order für darkstar-alikes under the standard covers. Thanks to this forum i could supply the specs.

The pole screws in the gibson beast do not have any noticeable effect. BTW: its sound is cold and it lacks "upper bass / lower mids". Like a heavy-metal-screaming-super-distortion guitar pickup would sound in that position (i had tried such PUs in my RD bass). Must be played REALLY loud in order to be audible.

[David King]

That sounds truly awesome! I'll take a dozen please with a side of kimchi.