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DarkAvenger last won the day on May 2 2013

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  1. Well, I was actually thinking about using a few small pole pieces that could be soldered into the board on either side of each coil. Mumetal tape will saturate very quickly, so it may need to be thicker to effectively shape a magnetic field.
  2. Getting more out of less. That's great with the SNR. If you could get more signal out of the coil with less noise, couldn't you use a more power efficient opamp? Also, reducing string pull is always a good thing. I guess I'm just giving you suggestions. I would also advise against mumetal at first, unless you have a source already. I've experimented with it and while it does help, I think you would benefit more from the overall magnetic design rather than jumping to mumetal. Certain stainless steels work well for this application and are easy to find. Also, I'm not suggesting anything too radical, just some simple experiments you could try. As I've said before, these modifications will need to be tuned to what your trying to do. The quickest and easiest way of doing this is with a few tests. Food for thought: Simply put, Inductance = Permeability x ((#Turns^2 x Area of core) / Length of coil) Neo magnets have a relatively low permeability but strong field strength. Shielding is merely an easy path for the magnetic field to travel back to the other pole.
  3. No, just steel. I know proportions and details aren't exact, but it's a rough idea. To be honest, FEMM isn't going to simulate a pickup. There are much more complicated things going on, in 3D and AC. It can help you visualize the basics though. What your looking at, there are six coils with smaller metal rods between them. The rods are much darker than the ferrite core of the inductors. The two smaller boxes on the outsides of the pickup are the adjustment screws, or a representation of them.
  4. Well, no. I imagine you will still have crosstalk relative to the original design, just to a lesser degree. It depends on how well the original design performs. Another factor to consider is how close the pickup can get. The closer the better, however if it's at the neck position this won't be possible. Also, if placed near the neck you will need to worry about string bends and the magnetic field. It's a lot of trade offs and balancing once things are refined, but the general applied concept could improve things. Basically, a larger magnetic field will have a bigger, possibly wider, sensing area but will be more susceptible to noise(magnetic) and crosstalk. A smaller field needs to be positioned more carefully. A stronger magnetic field relates to output, but does correlate since there are other factors to consider, largely inductance but there are a few more. Since the plan is to still use the neo magnets, the field strength may be stronger than the project above. Again, a lot of it is a balancing act of size and intended use.
  5. It's fairly rough, but as you can see there may be something to gain. A tighter field will result in less noise in, less string pull, less crosstalk, and in this case more output since the coil's core is now increasing the inductance. Less noise and more power in the pickup stage means less power can be used in the amplification stage and maintain a low noise level. The idea above is first use a ferrite core in the inductors and then shape the field using neo magnets. There is plenty of experimentation to be done to see output and noise levels with different configurations. A neo magnet has a lot more pull to itself and thus the relative usable field isn't projected as far, well sort of. This is good and bad. Another good thing about experimenting with this is the only modification needed to the original design in order to experiment is a change to stock coils rather than the neo coils. Another way to help shape the field is through the use of fins, or even small poles or rods, to give the magnetic field an easier path back to the other magnetic pole. This can also be good or bad. Good if balanced with your needs, bad if it removes most of the usable magnetic field.
  6. It's very rough, but... instead of this
  7. I like it a lot! Very clean. I'm still not convinced on the neo magnets though, and you could still improve the magnetic design aspect a bit. If you can squeeze a bit more output from these coils then that would be less noise out since a big source of noise is from amplification. Also, narrowing or manipulating the magnetic field will improve issues with noise and crosstalk. Do you have room under the pickup to place magnets? Or room for a small and compact enclosure system around the coil sets?
  8. FEMM 4.2 is a free magnetic modeling program. While limited, it can be very useful in visualizing magnetic fields and relative strength. I would suggest researching noiseless stacked coils for some examples of use of neo magnets. Lace pickups also have many interesting concepts, though many remain patented. As for the bifilar coils, I'd be more interested in output vs size (sensing area related) Of course, these coils would have little effect on noise ratios from a design standpoint, and would need to be wired as you are doing with sets.
  9. Nice! Looking good so far! For a low power version, perhaps there are other opamps to consider? You could probably run on less than 1mA... for all 6 coils. I suppose your using neo magnets? If you haven't already, I'd suggest playing around with FEMM a bit to see if you can improve magnetic containment a bit. To be honest, I'm not sure neo mags are the best way to achieve what your trying to do. They can be useful, look at ways they have been used in pickup design historically. I suppose in a way this goes hand in hand with bifilar winds too. Speaking of, did anything come of the bifilar windings? Any reason for or against it? I still have a project(on hold for the moment) based on bifilar designs. Keep up the good work!
  10. In all honesty, I tend to find harsh criticism very helpful when forging new ideas... as long as it's not taken personally. I don't think that line has been crossed here, but others may feel differently. Back to the question at hand... Yes, you can do it that way. It's harder to do with very little benefit and more risk, but possible. I think there are ways to mimic the look of a one piece neck that would be easier to pull off with less risk and more precision. Also, don't fall into that 'tone' crap everyone rants about. A more important aspect to the success of your projects is quality, the best theory with bad quality is still crap.
  11. Unfortunately it is a million miles away. Also to clarify, there are multiple ways of wiring a bifilar coil and one is relevant here, 'bifilar series constructive' as I call it. Anyway, a stacked coil is basically adding a dummy coil to the bottom of a single coil to cancel EM noise. The dummy coil is magnetically isolated, to a degree, therefor when wound backwards relative to the coil above it does not cancel out the magnetic signal from the string's movement.
  12. In all honesty, I think moving toward a trussrodless design could be a good thing if done right. Agreed, a trussrod is an elegant solution to an undeniable issue. However it's also a 50 year old solution, and as far as I'm aware carbon fiber wasn't as reliably available (or cost effective) back then. There are some benefits to a CF stabilized neck. For one, there are not moving parts in the neck and if done correctly could benefit the setup process and reduce the time frame on the first setup. I usually wait a minimum of two weeks for the wood to settle in after the initial setup on a new guitar, a CF neck might not have these restrictions. Also, you might be able to create a new stable neck joint style if you're creative with it. Carbon fiber seems to be one for those building materials that guitar players like, for whatever reason, and is generally considered to be a 'neutral tone', so you'd have that going for you too. There's nothing wrong with moving on from tradition, you can look at advancements in many industries these days and find traditional methods being replaced with simpler solutions that weren't possible originally. Truss rods aren't going away(ever ever ever) but they aren't necessarily an end all solution. There is a bit of room in the industry for ideas like these, if pulled off correctly. Back to the original subject... I wouldn't put a truss rod under a glue joint. I have no basis for this, but I don't see a point to do it this way either. I'd just glue a matching fretboard on if I wanted the neck to appear one piece.
  13. A bit late, but I'd say a guitar without a truss rod would be entirely possible. Similar to your idea, you could route a deep channel on both sides and insert a thick strip of something like carbon fiber. A bit expensive, but it should work. There are also ways to stabilize the carbon fiber in the wood, if you were to try it then it's something to consider. You could also devise interesting ways of connecting the neck to the body with this method. Or you could cheat and use nylon strings =p
  14. It's fairly hard to compare such different designs. Impedance and inductance and a number of other factors influence the sound. In practice, testing will prove more vital since I honestly don't know where that cutoff point will become noticeable. There is also still the question of whether high frequencies are desired and to what point. The simple answer, preference.
  15. Why not use/make step up transformers? Or for that matter, wind larger pickups, higher output, thus less amping needed. I don't think it will alter the result too much, maybe to a slight degree but nothing too dramatic. However, keep the drivers the way they are. For the pickups, once the impedance (not resistance) is greater than about 25k, you will need a small jfet preamp to lower the impedance when inputting to an lm386(50k input?). However, with a larger input you will need less amplification, eliminating oscillation from high amplification and reducing the power needed in addition to the possibility of reducing noise in the system which in turn will improve your results. Just some thoughts to leave you with, the inductance of a coil is related to the square of it's turns. Inductance relates to output. A coil less than hmm... say, 1k ohms? is probably wasting output with very little benefit. There are quite a few other variables that effect such things such as design or wire gauge or metal mass nearby, I'm not quite sure where a DC resistance measurement would be exactly... but that's my guess for your design given the facts I know. The best test will be to wind something up an try it!
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