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Post by Charlie Honkmeister on Jan 3, 2022 11:06:29 GMT -5
Just FYI, I am also a big fan of Lawrence/Wilde (Becky and Shannon) pickups and have L-500, L-90, and Microcoils in my stable.
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Post by Charlie Honkmeister on Jan 2, 2022 20:14:30 GMT -5
Based on Charlie's experimentation, I figured I wouldn't worry about balanced output. But if it's that easy, sure, why not? Yes, floating balanced would work too. I experimented with floating (not very much) but that was with a 1K:10K submini audio transformer so there was a complete loop between the pickup and transformer.
You can in fact go single-ended and go into a balanced input, but you lose 6 dB (1/2) voltage signal and are more susceptible to noise from long cable runs or crapola shielding in the cable. This may or may not be an issue depending on your setup . The mic preamp I used, the ART Tube MP Studio, has both single-ended and balanced ins and outs; ART is still making them and they aren't super expensive .
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Post by Charlie Honkmeister on Jan 2, 2022 13:20:25 GMT -5
Mike, that's certainly another way to do it and it probably yields theoretical and practical advantages.
But from my experimentation a few years back, just "vanilla" humbucker construction, with the bobbins wound with AWG 36, even running single-ended, with normal precautions on guitar shielding and grounding, yields an exceptionally quiet signal anyway with a decent mic preamp, or transformer/medium gain preamp. I used an ART Tube MP Studio preamp to test.
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Post by Charlie Honkmeister on Jan 1, 2022 21:49:07 GMT -5
It's really easy to get a balanced output with a humbucker design - just invert the phase of one of the coils relative to a normal humbucker, and use the center coil split point as ground. But volume and tone control become more problematical since you have two signal phases. Not quite following how that would work. Is the second coil like a "dummy coil" then?
Sorry, that was confusing because I threw together two different ways of thinking about doing this. My bad and I hope that the following helps.
If you build a low impedance humbucker and let's say, just wire it exactly as a regular pickup would be with both coils in series, a ground and a single output, then to convert it to get two balanced outputs, one output from each coil, you just need to move the ground to the center series link between the coils; your old ground wire is one coil output and your old "hot" pickup output is the other coil's output.
In a regular single-output ("single-ended") humbucker, the two coils are connected electrically out of phase overall and the magnetic polarity is opposite between the coils, so the two reversals cancel for the string signal, and the induced current from the string motion on the single output is in phase, while the electrical hum/noise from each coil is out of phase and cancelled inside the pickup.
When you use a balanced input with 2 connections ("legs") and a ground, you do the exact opposite.
When you go balanced with a pickup, you actually want the coils to be in phase with each other so the hum/noise induced is equal on both outputs, and then that will cancel out downstream, because a balanced input rejects the same signal on both input legs and accepts differences between the two input legs. For balanced operation, you want the induced current from the strings from the different coils to be out of phase, or as different as possible, on the two coil outputs to the balanced inputs. So if the coils are in phase, then the two coils' outputs for string motion will be out of phase like you want, again because of the different magnetic polarity present on each coil.
An overall way to sum it up is that in a single-ended humbucker, the hum and noise is cancelled inside the pickup, but in a balanced output humbucker, the hum/noise comes out of the pickup, exactly equal on both outputs and is cancelled by the way the balanced input works.
This is the same idea for any hum/noise picked up in the balanced connecting cable; the induced hum/noise will be equal on the two signal wires in the cable and be rejected as well. Low impedance is much less susceptible to induced noise/hum anyway, so this is why low impedance balanced inputs are used for microphones and professional line-level audio connections, especially for microphones.
I hope that somewhat mangled explanation helps; I basically don't have a drawing tool handy to show this easily, but could be motivated to draw this up if there's enough interest.
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Post by Charlie Honkmeister on Jan 1, 2022 15:23:59 GMT -5
Hey there Mr. newey,
Here's a couple of tips. I did a whole journey on low impedance pickups a few years back.
1. Pickup Makers Forum - there's a years-long thread and significant other threads on low-Z pickups. A search will get you lots and lots of information. Of course the ultimate low-Z pickup is a single turn of very thick (so very low resistance) wire, or making the string itself the primary loop. The Lace Alumitone is a single turn loop (actually, two for humbucker) that actually is a transformer primary, with the secondary a conventional coil with very thin wire.
2. Personal experimentation
I was finding during my own low-Z experimentation that AWG 36 works well for both normal Strat-sized single coil bobbins and humbucker bobbins. Use "normal" pickup parts, magnets, bobbins, etc. Just fill the bobbins up. You end up with around 50-70 ohms DC resistance, 100-200 ohms source impedance, and that works nicely with a 600 ohm to 1K Ohm balanced mic input since the rule of thumb of source impedance to preamp input impedance is usually 1 to 10, but you can get by with 1 to 5.
It's really easy to get a balanced output with a humbucker design - just invert the phase of one of the coils relative to a normal humbucker, and use the center coil split point as ground. But volume and tone control become more problematical since you have two signal phases. You can run single-ended inside the instrument, like Gibson did with the Les Paul Recording models, and use an external transformer to convert to balanced. here's a thread on GNuts2 about the LP Recording model with a schematic:
Pickups with this voltage signal level need about 25-35 dB gain to be the same level as "vanilla" to hot hi-Z pickups. That's absolutely no problem for a mic preamp. If you also want a "normal" output on the instrument, there's a couple of ways to do it. It's tough (but possible) to get an onboard preamp with that much gain, that's also quiet, and does not pull so much current that it would suck down a 9V battery fairly quickly. Another approach to on-board is possible. Mini or submini audio transformers with a 1K primary to 10-15K secondary (or vice versa) can get you up to about 17 dB of this noise-free. A simple JFET preamp can get you the other 6-18 dB or so without too much noise. Putting the tone and volume after the transformer or after the preamp lets you get closer to "usual" or easily-sourced values for your volume and tone pots and tone cap.
The Fishman Fluence pickup line is built low-Z, with a multilayer PC board with printed wires and stacked, then has an active preamp with tone shaping to supply the gain and emulate the resonant peaks of conventional pickups.
3. Do you need "Flat to 20K" ?
The self-resonance of these pickups is way up in the ultrasonic range - 25-40 Khz. This means that by themselves they are ruler-flat in the audio range we are able to hear. That's OK if you are going to do all your tone shaping with electronic EQ. But for a guitar, do you need any output from the strings over about 7-9 Khz? The answer is, No. There's lots of funky noise up in and above that range you don't want to hear - string squeaks, pick noises, etc. Also, metal strings go non-harmonic up there just due to physics and so those "harmonics" aren't useful. Also, for the normal electric guitar sound we expect, almost all guitar speakers drop off a cliff in output over 5 Khz.
Don't let me talk you out of making low-Z pickups for that reason -- you can get wonderful, acoustic-like clarity and immediacy out of these pickups, and EQ is relatively easier with a flatter source. But be ready to apply EQ to get back to something that also works as regular pickups do with "normal" amps and pedals.
Take care and Happy New Year, -Charlie
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Post by Charlie Honkmeister on Dec 31, 2021 19:58:33 GMT -5
... What the main idea here is for experimentation, is to connect the two coil split points (AKA series coil link ?) from both the bridge and neck together, and use a series resistor/capacitor combo to connect that to either ground or hot to do the partial split.This is also true of the above wiring too (the Jazzmaster, not that it's any surprise that DW seems to have failed to notice this, or at least didn't understand the implication this has) — and to be honest I'd call this approach cheating. (This also partially answers sumgai's earlier musing of this idea: b) I have, without thinking about it at first, implied that one must use 2 resistors and 2 capacitors. If one were either cheap, or needed to conserve space in the cavity, one could just as easily combine the two switch pole terminals, and send the "single coil" connections to ground through the same resistor/cap combo. As to what the sound will be like in doing so, I haven't a clue ) When the series links of both humbuckers are joined together (and partially split via just one impedance), how many coils are contributing to the output? Say we have the neck partially split: we have the full output from one of the necks coils, reduced output from the other neck coil, and that's it right? Nope! With connected series links you'd also have a (roughly) equally reduced output from one of the BRIDGE coils! (Assuming your switching scheme doesn't deliberately avoid this by un-grounding the supposedly disengaged coil.) ... There's another way to look at this twist on the "partial coil split." Once we do a partial split of one PU and introduce some of the shunted coil back in, what we're doing just from the point of view of the output and the "naked" unshunted coil, is introducing another RLC element either above or below the unshunted coil. Adding the coil from the other PU to the shunt RLC just modifies that RLC that's in series with the naked PU coil(s) that is/are selected ( from a passive component point of view), and makes that combined shunt RLC impedance constant for any selected PU combination.
From a signal generation point of view, you have some sort of a constant filtered mix of both shunted coils that can add to (in a gross signal sense) whatever "naked" coils are selected on the 3-way. So, as you are pointing out, when you split in this way, you really never can get just one pickup any more when the split is engaged. But maybe that's not such a bad thing.
Because of seeing it done this way in both the Jazzmaster design and the Strandberg design, and also hearing the results when I tried the HSX, there's some indication that adding that constant mix of both shunted coils is sonically useful for all positions of the 3-way switch, maybe even better than partially splitting the pickups individually.
Thanks for catching that the Jazzmaster is connecting the split points together.
It ain't cheating if it sounds good IMHO, but if it makes some people happier, we can call it something else besides a "partial coil split." Maybe "aggregated hybrid coil split" or something like that.
Both in the Strandberg and in my own testing, the active coils are the inner (inboard) coils and the shunted coils are the outer coils. I haven't sussed out the S-1 wiring on the Jazzmaster but I wouldn't be surprised if it was set up the same way.
Along the lines of different RC shunts for the two pickups, I'd also like to suggest that one can put a resistor between the two pickups' split points to partially isolate or rebalance the "mix" and also be able to make a single RC to hot/ground have more effect on the neck PU side or more on the bridge PU side. Just tossing that out for the bold and adventurous with more time than I have.
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Post by Charlie Honkmeister on Dec 31, 2021 19:13:39 GMT -5
All of these circuits would meet your requirements for a single switch that splits both pickups at the same time with one switch. Possible exception of #1 below. ... 1. TDPRI Partial Coil Split Theory and Discussion TDPRI Partial Coil Split Theory and Discussion - Moosie... There's a 4PDT mini switch available if you can tolerate a separate mini split switch instead of a 2PDT push-pull switch that's ganged with a pot. While you could use a 4PDT for that scheme, a DPDT would also work (one SPDT per HB). That scheme is almost but not quite exactly the same as the one I posted above. Yes it's tuned and arranged differently, but the only real change is that Moosie's 6k2 resistor is in parallel with the coil rather than coil + cap combination. (The other resistor I have, parallel with the cap, is the counterpart of the later added anti-pop resistor.) Thus the 'fix' to turn mine into an equivalent of Mooise's is to swap the wires that connect either side of the cap to the switch. Yogi, I definitely buy the idea that your version would work; the bass cut cap placement isn't critical and using your scheme would save one set of switch contacts that would be needed in Moosie's version to short out the cap for full humbucker mode. I mentioned the mini 4PDT because I've recently been experimenting with this and the 4PDT allows a larger range of things to try.
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Post by Charlie Honkmeister on Dec 31, 2021 11:03:41 GMT -5
Hey, just another reference here.
(Please indulge me if you know this stuff already, but this thread is going to be found a lot in searches on the forum, coil splits are a very timely topic, and I wanted to give new folks a good set of references in the thread instead of them having to search in dozens of posts.)
If you are doing total or partial coil splits on both PU's with one switch, you have two pickups from the same manufacturer, and you want, let's say, the north coil on one humbucker and the south coil on the other humbucker to be active, you normally split one PU to hot and one PU to ground.
If you want to split both PU's to hot or ground, use north coil of one pickup and south coil of the other, and retain some hum cancelling when both bridge and neck are selected and the split is active, you will need to wire one of the PU's "inside out."
("Inside out" may seem confusing; what you really do is "re-stack" the coils from ground to hot, but "inside coil split point wires go to outside and outside wires become new split point" is definitely too long.)
Here's a good, well-written link with text and diagrams to explain this idea. It uses DiMarzio pickup color codes but you can easily understand and translate this to other PU manufacturer's products.
Flipping the magnet together with inverting the polarity of the pickup hot/ground connections would do the same thing as "inside out", but with the big disadvantage of having to open up the pickup.
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Post by Charlie Honkmeister on Dec 31, 2021 9:49:45 GMT -5
You're not going to get much by switching tone pot values; especially if you are doing the 3-way on-on-on series/split/parallel on the bridge pickup. Ain't worth doing IMHO.
A toggle switch which allows the series/split/parallel setup ( has 2 poles as DPDT on-on-on, and 1-2 poles of whatever) is going to be a very challenging parts search, as newey mentions above.
A tone pot with capacitor is still mostly just a resistive load to the AC pickup signal until it's around halfway down. So, unless you like mudtone, just shunting the 500K volume or tone pot with a 500K (470K or 510K standard value) resistor will do basically the same thing. But then, you've improved just one mode out of series/split/parallel.
I think that having one really good-sounding partial split is better than having series/split/parallel on the bridge. This thread is on the right track. I've tried a lot of things over the years. Partial split works better in not having the pickup sound too thin, it works better in terms of less output drop, and it works better in that you don't totally lose hum-cancelling, and you can trade off these qualities to a certain extent and have a greater chance to get to a sweet spot that you like and that works for your rig and what you're playing.
I do like parallel coils for the bridge, especially for super-hot bridge PU's, but it's such a radical change in inductance and DCR (1/4 of the inductance and DCR of the series coil connection) and output that you need to optimize the rest of the volume/tone circuit, and gain and EQ in your amp/pedals, to get the most out of it. And then, it's a hassle to try to make everything work in combination with the other PU's in the instrument. And then, tweaked as far as it can go, it still might not be as good as you want it to be for real single coil -oriented musical styles.
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Post by Charlie Honkmeister on Dec 29, 2021 9:42:05 GMT -5
Frets,
This is a very timely topic for me as well and I'd like to offer some really good links and a little bit of my own experience on partial coil splits. Some of this has been talked about on this thread, and I think you are well into approach #2, but I wanted to give some of the material "fresh" for reference for some folks in the community who might need it.
All of these circuits would meet your requirements for a single switch that splits both pickups at the same time with one switch. Possible exception of #1 below. Yeah, there might be a couple of parts hanging off the switch, but that's why God invented heat-shrink tubing.
1. TDPRI Partial Coil Split Theory and Discussion
Great straightforward explanation and diagrams here. Moosie mentions the PRS partial split method they use on the S-2 and Core HH models - a simple resistor shunt of one coil. He also mentions a method tried by Gibson - just a capacitor to shunt across one coil.
The interesting thing about Moosie's approach is that he uses a bass cut cap between the coils and then uses a simple resistor shunt to either hot or ground to attenuate the desired coil in the humbucker.
Moosie has done a lot of work on experimenting and listening (including building test rigs) and I think his approach is a great starting place. I have built this into one of my project guitars and it does work. (Really well, but I'm in love with approach 3 below.) Hats off to Moosie. Whether Moosie knows it or not, he's in the GNuts2 tribe.
There's a 4PDT mini switch available if you can tolerate a separate mini split switch instead of a 2PDT push-pull switch that's ganged with a pot. You could do just about any scheme you wanted (including series/parallel coil switching) with one of these. I have bought these and am using one, and they're just fine as well as very compact.
2. Dirk Wacker - Ultimate Guitar, Fender Select Carved Top Jazzmaster
Dirk discusses the partial coil split found on the Fender Select Carved Top Jazzmaster. It is a capacitor and a resistor in series, to shunt the selected humbucker coil.
There's some interesting discussion on different coil split approaches and suggestions for component values, but Dirk kept it pretty non-technical, which might slightly frustrate some of the electronics and theory folks here on GNuts2. However, Dirk did a great job of providing enough information to allow a good start for experimentation.
3. .strandberg* HSX Circuit
This is a partial coil split circuit that Strandberg (.strandberg*) has introduced in conjunction with their Michael Frank-designed pickups, on certain Strandberg models, particularly the
Strandberg Boden Fusion 6 LE Titanium.
The module is available from .strandberg* separately for $44.00 plus shipping.
The module has four wires - one wire to the coil split point, one to ground, one to pickup output hot (top of volume control), and one wire to the wiper of the volume control.
This is an epoxy-encapsulated sealed circuit and I haven't really tried to reverse engineer this, but as a total guess, this "looks" like a combination of a treble bleed across the volume, combined with a partial coil split which uses BOTH split points on both the bridge and neck pickups at the same time (in other words, connects the two "coil tap" points of the two pickups together regardless of which pickup is selected, and uses probably a capacitor and resistor in series from that point to perform the shunt/coil split. I could be and probably am wrong, but this is what it smells like. If you look at the wiring diagram above, this is done with a single 2PDT switch like you wanted.
What the main idea here is for experimentation, is to connect the two coil split points (AKA series coil link ?) from both the bridge and neck together, and use a series resistor/capacitor combo to connect that to either ground or hot to do the partial split.
A 3.9K Ohm resistor in series with a .047 uF cap would be as good a starting place as any for this mod, using Dirk Wacker's suggested values for a single pickup. Yes, I know that those values are suggested for a single pickup and we are doing both at once with one shunt, but let's start somewhere and season to taste.
Whatever the circuit topology is in that little module, the results as I tried in my own guitar with the splits engaged, are very close to PFM (Pure Freaking Magic.)
I want to add that my wiring configuration is shunting the outside coils of the neck and bridge and using the inner coils full strength. This is identical to what Strandberg does but it seems a bit counter-intuitive since the outside coils have the most bass and treble, one would think. But I can't argue with the results.
There's definitely a lot of midrange cut; the sound of both the neck and bridge pickups selected separately when split, sound definitely "acoustic-like" but also "single-coil-like". Super useful and musical.
However, the "both pickups selected position" - gives a very usable, Knopfler-eque, Strat position 2 (neck/middle) quack! From a 2 humbucker guitar no less! I would not have believed it if I hadn't heard it.
The bridge by itself when split has a very,very slight touch of "quackiness", but sounds extremely good for a single-coil emulation. A hotter bridge PU might shift that balance a bit but I'm happy with what's there now.
There's been some discussion on the DiMarzio forum about the HSX and the poster (1) wasn't very impressed with the Fusion 6 pickups/HSX combination, (2) believes that the HSX would work best with vintage type lower output pickups, and (3) believes that you can get further for a lot less money with just a series resistor/capacitor shunt a la Dirk Wacker article under #2 above, just as I'm suggesting.
I was using a 4.3 Henry/6.1K DCR neck rail pickup (wound with AWG 41) built with Mojotone parts, and a commercial Calig rail pickup (Calig H67) with 6 Henry/8.8K DCR for the bridge. So maybe my PU's were in the range that the HSX will work best with. If you can replace a $44.00 module with 85 cents worth of parts, I'm down with that.
Also BTW, notice on the Strandberg wiring diagram that there's a 12K resistor on the tone control. This is a Very Good Thing; it lowers the tone control loading a little bit, and partially prevents complete descent into the "mud zone" that most of us despise with the traditional tone control when it's turned all the way down. Since someone decided to put that on a $3K+ guitar with a single tone control -- sure, I'm going to pay attention.
If there's any way I can get Michael Frank ( I believe this is the same person as Michael Frank-Braun, chief engineer at Fender) to reveal the HSX circuit for us DIY experimenter types, I will do that. But based on history and the Fender Jazzmaster circuit which I am inferring that he had a part in designing, I think we can get to a reasonable facsimile of what I found with the HSX by trying out the topology I outlined.
Take care, -Charlie
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Post by Charlie Honkmeister on Nov 4, 2018 1:23:46 GMT -5
Thanks, I'm only on here occasionally too so it might be easier if you just gave me the calculations that I need and I can figure out the numbers my self. More about the switching scheme of my guitar. So you say with this fancy tone knob I won't need all that? In case your interested this is how it's wired, I adapted it from Briguy on the SD forum: S1 volume that controls phase (it automatically selects the proper pickup based off the rest of the circuit) 3-way rotary switch. This switch works in combination with the 3-way pickup selector to get all the neck/middle/bridge in position 1, neck+middle/neck+bridge/bridge+middle (all in parallel) in position 2, and neck+middle/neck+bridge/bridge+middle (all in series) in position 3. And then the 3rd pot would be variable resonant frequency. With the variable resonant frequency control, what parts of this wiring do you think would be made "obsolete"? I tend to believe the 2.0 Henry inductance for the Wilde L-45's, but if you can measure it exactly with an LCR meter like an Extech or DER EE DE-5000, and also get me the DC resistance and either the pickup capacitance or the self-resonant frequency of the pickup(s), I can work the circuit simulation to give you a good range. It would be easier to share a Circuitlab link using a good set of starting values. But you need a good set of measurements on your pickups to really tweak the resonant frequency range of the tone control.
If we ignore output changes as you change your switching configuration, the electrical main effect of doing a pair of pickups in series rather than parallel is to double the inductance of the combination when they are in series and halve the inductance when they are in parallel, relative to a single pickup. This affects the resonant frequency given a fixed load capacitance or a certain fixed point on the variable frequency tone control. That being said, having a quick way to change parallel to series combinations can give a volume boost and a drop in resonant frequency before cutoff, which might be useful for, let's say, a solo break in a song.
The variable resonant frequency tone control typically will be dialed in for a bit under a 1 1/2 octave range, let's say for an example from about 1.7 KHz to about 4.3 Khz, which covers humbucker tonality all the way through bright Strat or Tele type tonality with cable loading, all by itself. This works the best with the widest range of amps and pedals. So I would say that sticking with either all series combinations or all parallel combinations of two pickups would be OK without having to switch to the other mode, and having both modes as alternatives to the normal single pickup selections is redundant.
I would vote for keeping just "normal" and series modes available because the lower resonant frequency at cutoff in series versus normal single selections or parallel is "better" for hitting good distortion tones from a pedal or amp, and it also gives you an output boost for the two-pickup combinations. But it's really all about what you prefer, your style/genre of music, and whether you are going to play the instrument live and don't want to deal with a lot of switching in mid-song.
The phase switch wouldn't be redundant in any case.
-Charlie
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Post by Charlie Honkmeister on Oct 31, 2018 20:53:26 GMT -5
Christopher,
I apologize that I haven't seen the board in a bit. I will try to answer your questions.
1. Yes, the component values have to be recalculated based on the measurements of the pickups you are using. I measure the pickups with the techniques found on this board, and plug in their values into circuit modeling. I use CircuitLab (www.circuitlab.com.)
If you can measure the pickups (inductance measured at 100/120 Hz, DCR, capacitance) I can plug those values in to get a good resonant frequency and Q range for the tone control, or, alternately, I should be able to share the Circuitlab link for the circuit so you can do this yourself (I think that you can run values for a shared link; you just can't save the circuit unless you are a member.)
2. Generally, different switching arrangements work the same way you would expect with a normal passive circuit (parallel, series, coil splitting, etc.) The overall inductance (primarily) changes with the switching arrangement so the "range" of resonant frequency adjustment changes. (This is oversimplified but mainly accurate.) In general, I have found that the variable cap tone control is so versatile that I don't find the need for extremely complicated switching arrangements. But they will work just fine with this circuit.
3. I don't have any sound samples yet since I am pursuing the "right" tone settings for several configurations (2 humbucker, 3 single coil, etc.) and still tweaking to get the best tones. But I am very close and will put up some sound clips fairly soon. I'm also going to do a longer post on this technique since the implications of this are pretty interesting - basically with this platform you can "tone-engineer" an instrument's electric voice within limits to suit the instrument construction, pickups, artist, genre, amp/signal chain, etc.
Please feel free to drop me a PM if you need some more information.
I agree with your taste in pickups - formerly Bill and Becky, and now Becky and Shannon are making some great ones.
-Charlie
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Post by Charlie Honkmeister on Oct 21, 2018 9:19:46 GMT -5
JohnH said: "The two piezo volumes will interact and affect each other."what about one of those dual gang blend (sometimes called pan) pots? I have one in a two pickup bass and LOVE it instead of the standard jazz bass wiring I had similar thoughts as John regarding master volume in addition to separate volumes for the magnetic pickups I would strongly suggest using at least 1 Megohm minimum, and 2-5 Megohm preferably, pots for the piezo discs.
500K , and especially two 500K's in parallel, will load the piezos down too much and mostly or completely kill the bass and lower midrange.
Buffering the piezos and mixing after the buffers would be a better solution. Another would be: going stereo output on the piezo jack, don't put any passive piezo volumes on the guitar at all, and buffer/mix with your external equipment.
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Post by Charlie Honkmeister on Aug 17, 2017 21:28:55 GMT -5
There's one more tweak to keep in mind on a piezo should you ever need it. If you put a small value capacitor (in the 1000 pF-.01 uF range for most piezo pickups) directly across (shunting) the piezo element, this pads down the output (reduces output level to better match the mag output or not overload the preamp,) can "tame" too-shrill highs, and also make the piezo less sensitive to resistive loading (giving more bass response for a given load resistance.) I'm glad as well you are making good progress on your piezo work. Thanks Charlie, and sorry I took so long to get back to you. First, your recommendations will be taken into consideration when the time comes. I and my friend are now trying to soothe some frequencies and boost others. John's preamp stands out, but to our ears, it lacks some tiny features, devil is in the details. We are mounting the piezo loaded saddles in order to find out whether those metallic, string-hitting frequencies are in fact due to the strings themselves or it's just a frequency-modeling feature a preamp must have. In order to achieve this, the piezo saddles will definitely guide us through. The preamp misses some bass thing and compression, needs some cutoff in the middle areas and also a boost in high frequencies. We don't want to bother you guys, but think it's necessary to keep you posted, since the project turned out to be available in this forum. If you're rolling your own piezo saddles and have some metallic, tinny, sounds coming out of the piezos, I've found that piezo saddle to metal contact (bridge plate, not strings) can cause this. I don't know how you're rolling these saddles so can't be more specific unfortunately. While you are experimenting, you might want to put some teflon pipe tape, either the standard thin kind or the 3 mil thick kind, anywhere that there's a significant area of metal to metal contact. The tape fills in the microscopic surface irregularities in the metal contact surfaces, provides a little bit of high frequency damping, and may help with zinginess or metallic high frequency harshness without impacting basic tone or output for the worse. Plus it's cheap and reversible. On some of the commercial stick-on piezo discs, the glue or adhesive probably provides this function and, as an anecdotal confirmation, at least one guy who makes high-end contact piezo discs, told me at NAMM that the actual adhesive he used was part of the reason his piezo sounded good. When you're doing piezos you need to look at the mechanical interface and attachment of the piezo first IMHO, then go for EQ when you know you have a good basically full range signal.
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Post by Charlie Honkmeister on Aug 10, 2017 15:40:17 GMT -5
The extra moving mass of a lower string compensates for it not moving so quickly. Here's how I idealise it: All strings in a set usually have about the same tension, so given plucking with a given force, they deflect about the same distance. The release of the string sets up a vibration amplitude which is about the same for all strings. Higher strings are moving backwards and forwards through this amplitude more frequently, so move faster than lower strings. Greater string velocity promotes greater rate of flux change and hence greater signal induced. But lower strings are heavier and so are moving more metal, which increases flux change to compensate for lower velocity. That's why naturally struck or plucked magnetic guitar signals from the strings aren't intolerably bright and the strings are relatively even in volume for a given pick stroke. We see the +6 dB/octave velocity "bias" of the fundamentals on the strings offset by the (roughly) -6 dB/octave contribution from the inductance of the pickup coil, and for the balance of all the string outputs, there's progressively reduced moving mass and flux generation of the higher-sounding strings for a narrow range of string tension.
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Post by Charlie Honkmeister on Aug 7, 2017 22:51:55 GMT -5
John, I appreciate it. Perfection can sometimes be elusive. I achieved much of my goal. I discovered the world of low cap values, such as .0033uF and .01uF, and am so far finding them better than the .022uF and .047uF values -- to my ear anyway. I may try the same concept with a 6-way rotary switch on another guitar to further check for "ideal caps" by cross comparing even more values. The G&L PTS (which you have written about) would also be great to try. You mention it may be especially useful on a humbucker rig, but I would apply it to a single coil setup, normal kind of windings, so not overwound at all but not true vintage either. Perfection can be tuneable. I'm really getting some great results with the bootstrapped variable capacitor using a buffer. Coil switching and serial/parallel switching schemes work fine but it's a different approach than conventional passive tone and volume controls. I'll have a new thread on this soon if there's interest. The old thread (albeit getting a bit dated) is at: Variable Resonance Pickups - Fun with Buffers -Charlie
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Post by Charlie Honkmeister on Aug 4, 2017 17:59:00 GMT -5
Well that's good progress. So are you now testing it in the guitar and hearing how it sounds? Before fine tuning, it would be good to know that your basic levels from the piezo and magnetic systems are close enough in volume to be useable. Then, its all down to adjusting tone and I expect it will be different in your case. If you have the full circuit built, then there are 3 EQ presets. R30 is a high-pass filter to control treble, it only lets signals through that are above a frequency determined by R30 and C6. Reduce R30 and this frequency rises. Similarly, bass is controlled by a low pass filter R29 and C7, increase R29 to lower the frequency below which it passes the bass sound. R13 pans between the treble and the bass. If you read through the first post, you'll see how in my case the main tonal fix that was needed was to knock down a hump at around 700hz. This was done by moving these two filters apart so there is a gap in the middle. Id recommend trying to test it the same way I did. Run the signal into the line-in on a pc and record it in an audio program such as Audacity (its free). Then you can see where your peaks are and decide how to set up the filter. Duncan's Tone Stack Calculator (also free)can be set up to match the tone stack in this circuit. There's a couple of other tweaks that you can try if you need them: If you are generally short of piezo volume compared to magnetic, reduce R23 at the first transistor Q1. If the piezo is lacking bass, increase the value of R2 (the 150k, as discussed before) If you need a little more very high frequencies add a small cap across R25 at Transistor Q4, maybe about 3.3nF. John, all I can say is that you rule man!!!! Your information always come in handy! Yes, we tested it on the guitar. It sounds good, but lacks some tweaking in the treble and middle frequencies areas in order to sound more electric-like. we are also trying to build piezo loaded saddles to get better and definitive results. I truly believe that we're gonna make it. we're not trying to exactly match GraphTech's results, but make a stand in the middle of acoustic and electric sounds. As soon as the sound files are decent, I'll let you know. There's one more tweak to keep in mind on a piezo should you ever need it. If you put a small value capacitor (in the 1000 pF-.01 uF range for most piezo pickups) directly across (shunting) the piezo element, this pads down the output (reduces output level to better match the mag output or not overload the preamp,) can "tame" too-shrill highs, and also make the piezo less sensitive to resistive loading (giving more bass response for a given load resistance.) I'm glad as well you are making good progress on your piezo work.
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Post by Charlie Honkmeister on Jul 27, 2017 20:46:02 GMT -5
Just as some new information, not necessarily a plug, I have found this piezo bridge to work well: brennerusa.com/product-category/piezo-one/This uses a single acoustic guitar saddle pickup (Artec) with 6 crystals in a common assembly with a single cable. Models are for Strats and Teles with modern string spacing, but they have been working on replacements for a wraparound Gibson type bridge. Besides putting one on a Strat, I have put one on a PRS SE trem and it works well there after milling a slot on the side for the cable routing. The bridge is designed so that each string saddle "finger" extension only contacts the piezo directly on its own element. Intonation and fingerboard radius compensation are machined in and can achieve good intonation and will work fine for Fender scale length (or PRS) and a normal range of string gauges. The entire bridge can adjust fore and aft, and up and down, in a similar way to a Gibson wraparound tailpiece. Pricing is extremely good on this unit ($65.00 US) compared to L.R. Baggs, Graphtech, and Fishman piezo bridges with individual piezo saddles (>$200.00). I have bought two of these and have a third going on my next Tele build. JohnH's preamp as well as other piezo buffers/preamps will work fine with this piezo. Fair disclosure: I found this bridge on Ebay, was intrigued by the design and pricing, bought one, called Mark Brenner to talk about it, and we ended up friends. But the innovative product came first. -Charlie
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Post by Charlie Honkmeister on Jul 8, 2017 23:26:56 GMT -5
That's the Guitar Nuts spirit, Antigua!
Nice post! You touched on several good points and again, great persistence on experimenting.
Really, on the difference between a HB in the Strat bridge and a SC , I would think you're right in that the lower Q of the humbucker plays a role. The lower Q, (and not everybody thinks about this), also means the rolloff after the resonance peak is not as steep. So the highs aren't getting rolled off as fast and apparently the slightly higher level of harmonics in the 2 KHz to 3 Khz range, where the ear is most sensitive, even if they're only a couple of dB different, could maybe make the sound a bit more articulate for the humbucker as opposed to a "fat" SC. Don't know, just something to think about.
There might be an effect also with a tube amp or amp sim where maybe a bit more low and low-mid frequency content of the humbucker could generate a tiny bit more distortion in the same 2 to 3 KHz range and even above, even when playing so-called "clean," that gives a perception of articulation and presence. That's the principle of the Aphex Aural Exciter - it generates a bit of high harmonic distortion which gets mixed back into the signal, and the audible result is more bright presence and "aliveness."
I'm also suspecting that the presence peak on classic guitar speakers may also interact with some of this, but you're starting in the right place.
It would be very interesting to chase this further with both a real tube amp, and a good amp sim like Amplitube 3, and then see how things pan out on this using the whole chain.
-Charlie
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Post by Charlie Honkmeister on Jul 6, 2017 22:03:44 GMT -5
I'm taking this guitar to Summer NAMM in Nashville next week as my electronics package demo instrument. Eklein/Flaxwood spruce composite neck, Zexcoil Z-Series ZVN5 noiseless pickup set, variable resonance tone control/system buffer on tone #1, neck/bridge blend on tone #2, Babicz full contact vintage trem, Ron Kirn silicone tubing trem mod, Wilkinson EZ-Lock tuners. Several design and component experiments were combined into this one instrument. They all worked very well and worked together, which almost never happens. I'm very pleased with the build.
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Post by Charlie Honkmeister on Jun 29, 2017 11:39:11 GMT -5
Of all the changes you might make to guitar controls, setting it up so that the tone control normally runs below ten is the simplest to learn to use because it just means that you use the guitar more like all your other audio devices that have tone controls. Also I find that a properly functioning tone control, which adjusts Q over the whole range, is more useful than a resonant frequency adjustment if you have just one of the two. This is especially true when the pickup is an sc replacement since you can set it up so that the res. fr. is at the top of the system response and then have a wide range of tones available with a single control. But preferences do vary, of course. To be honest, I'm not totally convinced yet, by listening and playing, that variable resonant frequency/constant Q is the absolute best way to go on Strat-type instruments, although I'm completely convinced on 2-humbucker guitars. So I appreciate your comments on using a conventional tone control with SC type pickups. One target for using a variable resonant frequency on a 3-SC Strat type guitar is to get the pickup resonance down to about 2 KHz, to be able to hit the Hendrix or SRV tonality with a Strat and still be able to "dial back up" and do all the other tones a Strat can do. Jimi did it (also by touch and technique, of course) by using a 50 foot crappy cable with a lot of capacitance, according to Bill Lawrence, and SRV did it (I think) by of course, touch and technique, but also by really large gauge strings, the tone control, and also paralleling to multiple amps, which added a lot of capacitance. I'm almost finished building a Strat-type instrument with Zexcoil Z-Series pickups, which has the variable resonant frequency tone control on the 1st tone pot, and a neck/bridge no-load blend pot on the 2nd. I'm eagerly anticipating testing and playing the new guitar and will be trying to discover whether conventional or "greasebucket" tone control, variable resonant frequency/constant Q, or variable resonant frequency/increasing Q with frequency, works the best. Since the guitar has an onboard buffer, any of those schemes can be done fairly easily without cable capacitance rearing its ugly head.
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Post by Charlie Honkmeister on Jun 28, 2017 21:07:18 GMT -5
I just wanted to make sure that in my last post I didn't sound contradictory to some of my other posts on this thread.
Having a pickup with a high intrinsic or maximum Q is a good thing because it means that from an engineering standpoint it is more efficient (there are maybe fewer eddy losses and lower wiring resistance, and/or a better magnetic circuit) and also it's more flexible in terms of being able to voice it externally over a wider range with resistive and capacitive loading.
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Post by Charlie Honkmeister on Jun 28, 2017 15:59:46 GMT -5
Even though the tone control can serve as a Q control, I'm thinking of this as a "trim" control, so that your primary tone control can be parked at "10", and then a separate control can finely tune the Q factor separately. Figuring out where to cram these controls is probably a bigger challenge than anything else. An alternative would be to have a tone control with a detent, so that it has a "sweet" center spot that is easy to find. The Fender passive TBX control pretty much does this exact thing. The relative lack of popularity of these things goes to show the extent to which guitarists are married to arbitrary conventions, which is partly why I'm into studying existing designs and no so much interested in pickup design. Good ideas fall on deaf ears. It bothers me that people accept what they do, and will wax poetic about for pages on end, without really caring to understand how it works at a fundamental level. Wow, Antigua, that's about three interesting and "don't get me started" topics rolled into one. Couple of comments: 1. Really moderate resonant peaks with 5-8 dB of peak before rolloff, is typical of vintage passive guitar pickups and electronics, through a cable, into about a 1 Meg amp input resistance. I've been experimenting with Q and found that keeping Q relatively constant in that range, with series and shunt resistive loading, and just moving the resonant peak around with varying shunt capacitance, works pretty well for humbucker style tonality all the way into some Gretsch/Rick/Strat/Tele bridge-y type sounds. The problem with higher Q is that it also means a faster rolloff after resonance. And, with most amps and guitar speakers, the speaker starts rolling off about 5 KHz so unless you have a relatively high resonant frequency (think Strat and Tele), high Q works against getting at least some of those highs out, for "clarity" in cleaner to light crunch styles. Once you get into moderate to heavy distortion, you should limit bandwidth, but I don't think a high Q low-mid peak helps you there except for maybe extreme metal leads with lots of FX. If you're staying with trying to emulate "traditional" vintage tonality, staying with low to moderate Q values is the best course. Having a Q control which controls resistive loading is possible but I have a hard time translating that into something that a guitarist can make sense of and use in a live performance. That may have been a factor in the demise of the Dialtone product. Just because it's infinitely tweakable doesn't guarantee that it's musically usable or desirable for the player. I think that a single-knob variable resonant frequency tone control with more-or-less constant Q is a lot more useful and makes sense as a performance control that guitarists already think they understand, therefore don't object to. Of course, I've spent the last couple of years developing exactly such a control, so please take my comments with that in mind. 2. That being said, having a way to "trim" Q could be useful in a scenario where you wanted to emulate several pickups, or wanted to compensate for different series/parallel combinations of pickups needing different loading, depending on the series/parallel combination, to sound the best. But that would be done better with switch poles, rather than having a Q "trim" control as a separate pot on the instrument IMHO. -Charlie
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Post by Charlie Honkmeister on Jun 19, 2017 19:42:24 GMT -5
You can believe what you want, but it is the facts that matter. (For me, the six cols is also a way to make it convenient to get a high Q pickup.) ... Something different is occurring in the signal of an inverted/summed individual string pickup vs one master coil. We're not arguing whether its marketable, affordable to produce, or has some other desirable net gain, just that it's not the same, which brings me to the following: So you do not "believe" that the Zexcoil "original" with six slanted blade coils avoids the "DG" problem to a useful extent? ... As a player, I've always been able to tell the difference between the feel of different pole piece types and materials. It's not about the resonant peak. It's about how the pickup communicates transients and polyphony.... What Salo and Zexcoil fail to do is put the same magnetic interaction beneath the strings that the die hard Strat fan wants, or thinks they want, or simply demands cosmetically. In that way, and only in that way, I am saying neither are "useful" to someone in the engineering department at Fender, who is calling out for a traditional looking Strat pickup. The stack designs (although I'm not a fan of the sound of Fender's offerings) succeed in this regard, and their market acceptance validates Fender's design requirement. In the same way, stacks from Dimarzio, Kinman, Duncan, et al succeed at this as well. Frank, you're right about the die-hard Strat fans. Many of them actually put up with the hum because they are convinced that nothing replaces a "vintage" type Strat single-coil and don't want to change anything, including even the vintage pole piece stagger (which we know isn't optimum for modern strings and fingerboard radius) and bevel. The current crop of top-shelf stack designs starting with Kinman about 15 years ago, is very good as you say, but if you are talking about dynamics, attack, and some subjective "response" qualities that the "die hard" Strat single coil player is looking for, all stacks AFAIK are just a little bit sonically different in small but noticeable ways to a certain percentage of players. Fender has come out with several generations of "noiseless" stack designs and if something along the way pleased everyone, they most likely would not have had to continue R&D on stacks. But they all look conventional, or have just a plain cover without pole pieces on purpose, as you are pointing out. Your other implied point is well taken, that even if the design were better in every way, that any difference at all , either visually, or dynamic response/tone wise, from the subjective view of what a "vintage" Strat pickup should be, would be singled out and picked upon by a certain percentage of players. Scott Lawing acknowledged in an interview at Winter NAMM that the original Zexcoil visual appearance, with slots in the cover, was polarizing and turned a certain percentage of the players off. The new Z-Series has a solid cover with an embossed "Z" pattern that disappears at more than a foot or two away. Solid covers are probably more acceptable to a larger percentage of players than slots or "odd" pole piece configurations.
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Post by Charlie Honkmeister on Jun 18, 2017 13:26:23 GMT -5
ms- I think you're both saying essentially the same thing, although your explanation is more exact. The cancellation is never going to be complete or perfect, so it's fair to say the field of the one coil "disturbs" that of the other. "Partial cancellation" of the field is perhaps more accurate. Well, I do not think so, sorry. I think he saying that the disturbances in the two opposing magnetic fields cancel. Very creative, and likely to be accepted by most of those who believe "the disturbed field theory". There is still one guy on another forum who denies that the permanent filed magnetizes the strings because it is all done by disturbing the field.. Mike, I was interpreting Jarno's explanation to say that the shape and intensity of the static field(s) magnetizing the G and D strings is "disturbed" because of the adjacent opposite magnetic polarities, relative to the static fields from the pole piece/magnets magnetizing the other strings. So a static context, not a dynamic one with strings vibrating. It's still string-centric if you think about what and how much static field is reaching the G and D strings to magnetize them. A 3-D FEMM plot (if that's possible with that tool) of the Super 55 would show "funkiness" (sorry, couldn't resist) or lack of symmetry or intensity in the 3-D shape of the fields in the immediate vicinity of those strings, relative to the other strings. Jarno actually says he puts in smaller "helper" magnets to help in the "seam" region. That's actually a pretty interesting idea. But other than that specific case, the string-centric theory would suggest that it doesn't matter too much exactly how the strings get magnetized, as long as they do, and with pretty close to the same field strength magnetizing all the strings , all the time, even with string bending. That last part of course is where the Super 55 falls on its butt.
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Post by Charlie Honkmeister on Jun 17, 2017 23:18:36 GMT -5
Thanks for the specs. That is a low capacitance. Sounds logical, since like the Super 55, you have series impedances with six small coils instead of a clumped capacitance in a single coil. Given that there are six little coils, I would have even expected the capacitance to be lower. Do you happen to know if the Zexcoil blades are grounded? Mike, I don't know if the blades are grounded or not, plus, the whole pickup is potted into the cover and the pole pieces are covered by the neo magnets on the bottom of the PCB, so no easy way to check. Maybe I could ask Scott. The 50 pF is just a rough estimate from the resonant frequency and inductance. It might be a bit lower than that and I'll measure a bit better later, but really, it's quite low and that makes it very,very suitable for electronically varying the load capacitance over a wide range for voicing. -C.
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Post by Charlie Honkmeister on Jun 17, 2017 10:15:54 GMT -5
Probably the best-engineered (IMHO) example of getting a split-coil type pickup in Strat SC size with different magnetic and coil polarities on the top and bottom sets of 3 strings, and having it work well with no funny business on the D and G strings, would be Scott Lawing's Zexcoil design. Lindy Fralin's split blade design reputedly works well too. Both of these gentlemen have probably put hundreds of hours into engineering their designs, so it is apparently a significant challenge to handle the magnetic field transition between the D and G in a single coil size without compromising tone or output on the two adjacent strings. Yes, SL's design is very good. The slanted elongated coils keep magnetization and sensing by the coil constant over a reasonable range when bending. I believe there is some compromise necessary, and it is not possible to get high output with simultaneous high resonant frequency, but that is based on description, not actual measurement, and so I might be wrong about that. Mike, I just got a pre-production set of Scott's Z-Series "vintage" wind Zexcoils, and am building them into an instrument. The Z-Series is the second generation of his design. linkI can't say about actual output at this point, but the self-resonance is over 12 KHz measured with my Syscomp and a driver coil. Here's the other measurements (average for 3 pickups): Inductance: 2.817 H (120 Hz, DER EE DE-5000) DCR: 5.524K That makes the coil wiring capacitance around 50 pF. I'm really looking forward to hearing these combined with the variable resonance tone control in this new instrument. -Charlie
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Post by Charlie Honkmeister on Jun 17, 2017 2:08:31 GMT -5
Probably the best-engineered (IMHO) example of getting a split-coil type pickup in Strat SC size with different magnetic and coil polarities on the top and bottom sets of 3 strings, and having it work well with no funny business on the D and G strings, would be Scott Lawing's Zexcoil design.
Lindy Fralin's split blade design reputedly works well too.
Both of these gentlemen have probably put hundreds of hours into engineering their designs, so it is apparently a significant challenge to handle the magnetic field transition between the D and G in a single coil size without compromising tone or output on the two adjacent strings.
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Post by Charlie Honkmeister on Jun 1, 2017 17:01:33 GMT -5
Static magnetic fields don't count at all, which I'm assuming is what Antigua is saying about the coil. There's no such thing as a DC eddy current. The string is magnetized by the static magnetic field of the PU magnetic structure, and is the only source of time-varying magnetic field changes. Dr. Scott Lawing (maker of Zexcoil pickups) recently had a good clear post with an experiment which showed this. linkI, too, have spent quite a bit of time in explaining how pickups work and how they do not work, and Sl's writeup that you linked to is great.. But I do not think you are interpreting what Antigua wrote in the way he meant it, but maybe he will comment on that. Yep, Mike, I looked at it again and I think you're right. Sorry for a slight misunderstanding, Antigua, but I was maybe thinking you were using the coil-centric paradigm of how the darn thing works. That's really the most prevalent view that's in most of the articles that folks can find when they are researching magnetic pickups, including for example Hartley Peavey's pickup article. The string-centric theory fits pretty well with stratotarts' research into eddies in which he found that baseplate eddies aren't a significant factor.
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Post by Charlie Honkmeister on Jun 1, 2017 8:50:43 GMT -5
It stands to reason, too, that the magnemotive force of the moving guitar string is a lot greater than the force of the coil's own magnetic field, and so it interacts with eddy causing metals more prominently. The loss induced in the electrical circuit by eddy currents is a function of the frequency dependent impedance of the circuit element they introduce relative to the other impedances in the circuit. It is not a direct function of the relative magnitude of the two fields you mention. Static magnetic fields don't count at all, which I'm assuming is what Antigua is saying about the coil. There's no such thing as a DC eddy current. The string is magnetized by the static magnetic field of the PU magnetic structure, and is the only source of time-varying magnetic field changes. Dr. Scott Lawing (maker of Zexcoil pickups) recently had a good clear post with an experiment which showed this. link
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