outer "current coil" effect at play..?

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Georg
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outer "current coil" effect at play..?

Post by Georg »

Not very busy with steel these days - more important stuff on the table, but at times I need a break, so...

From the day I mounted a George L humbucker in the solid aluminum neck of my modded Dekley, the attack-sound from picking strings changed - very clear but not very strong attack-sound, compared with the same PU in a wooden neck where attacks sound not quite so clear but a lot stronger. The dampened attack-sound suits me and my style of playing fine, so up until now I never bothered studying why.

I know the solid and heavy neck/bridge construction resists string vibration - that's why I put it on, and this dampens attack some while aiding "sustain". But, if I place a PU upside/down above the solid neck - not inside it - the attack-sound relative to the "sustained" sound is stronger. This makes me wonder if the 20mm thick solid aluminum neck surrounding the PU completely - as a single-turn coil, actually picks up and "deflects" and/or steal/counteracts some of the initial peak as the string-vibration spread as an out-of-sync wave out from the pick-point until the string settles on a steady, "sustained", vibration. Whatever effect is at play here it certainly doesn't hurt "sustain".

As this is just a thought-experiment and I don't have the means/instrumentation to study any 'outer "current coil" effects', I am just throwing it out on the forum to hear what others may think or know.
richard37066
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Re: outer "current coil" effect at play..?

Post by richard37066 »

Ah, Georg - you've opened up another can-o-worms!

I'm mystified as to why the simple mass of the structure would attenuate an attack transient while supporting the decay ("sustain") portion of the wave. This implies that higher frequencies would be attenuated in like manner since the rise time of the attack should have a higher frequency component than that of the fundamental vibration - at lower frequencies, that is. Further, and as I understand it, there is a momentary period - measured in a few milliseconds - where the string vibrates at max amplitude before beginning it's approximate exponential decay. It would appear that there is another loss-factor at play, here. Hmmm. More electronic than mechanical?

In placing the PU upside-down you've probably altered the "capture aperture" - the length of the string being detected - thus the strength of the magnetic field surrounding the string. This, of course, is dependent upon the design of the pickup - a humbucker being an entirely different animal. Have you kept the pickup to string distance constant? In addition, it is the velocity of the moving string which generates an appropriate voltage output. That higher frequency component spoken about above. I'm far from being an expert in PU design and effects so I'll just toss these things into the air for consideration.

In an outlandish way, if the surrounding aluminum "single-coil" were not considered a part of the overall configuration then the only other thought that comes to mind is that of eddy currents being set up within the neck - a function of the proximity of the two. Haven't done my homework on this, but can this be considered another, although minute and momentary, "loss" that is unnaccounted for? Aaargh! Wish that my expertise were up to snuff in all of this.

Hopefully, I may have stimulated your fertile mind just a smidgen such that you'll persue this further. Just tryin' to help, as always.

Richard
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Georg
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Re: outer "current coil" effect at play..?

Post by Georg »

Richard, the "eddy current resistance" effect from the solid neck close to the strings - slightly closer than what's "normal", has crossed my mind.

The modded Dekley PSG with solid aluminum neck - as seen here...
Image
...doesn't really "bite" almost no matter how and where I pick, and I am unable to piece together all the electrical effects that may or may not be at play ... enough of a reason to perform thought-experiments around it.

What I am quite happy with but somewhat puzzled about when I compare my modded Dekley to my other PSGs - included an un-modded Dekley - through identical sound-chains:
- It doesn't "chime" easily - indicating attenuated high harmonics, resulting in a very clear, stable and dominant fundamental tone all the way up the neck.
- Output level at the moment of attack is to a large degree unaffected by "picking force". The peak is somehow naturally attenuated - maybe I can say "compressed", in the PSG itself.

With the PU temporarily fixed firmly above the neck in exactly same distance from strings and bridge, the attack-sound is a bit more like that of the un-modded Dekley. The sustained tone doesn't change noticeably though - the modded one "sustains" longer and more evenly.

Fun... 8-)
richard37066
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Re: outer "current coil" effect at play..?

Post by richard37066 »

Georg -

I don't understand the apparent contradiction between a lack of "chime" and clear fundamental tones all of the way up the neck. The simplest example is that of a "chime" at the 12th fret - this should be an octave up from the open fundamental frequency and should be the easiest to play. Ditto with the 24th fret - two octaves up. Yet you seem to indicate that even this is problematic. It would appear that if you were able to play a "barred" note at either of these positions with good fundamental tone then a "chime" would be equally clear. Ya aren't playing on 13-year-old raggedy strings are ya? ???????????

I'm certain that you are aware of a phenomenon which has confused a bunch of people but it's probably worth mentioning in the context of this thread.

To wit: - Changes in "loudness" are more easily discernable at lower volume levels. As volume levels increase, the ability of the ear to differentiate between an equal change in db level - low volume to high - is diminished. If one perceives the attack level at a higher volume to be approximately equal between two such strikes when - in fact - they are some 4, 5 or 6 db apart, then the resultant decay (a word that I prefer) APPEARS to be longer than it really is with an attendant increase in volume - but one which is overlooked (or not detected) by the listener. The attack characteristic is rather harsh and atonal thus confusing the issue. The RATE of decay is the same - all other things being equal - yet the string appears to "sustain" longer because of the increase - albeit small - in picking force.

Which brings me to the modded Dekley. The increase in the rate of decay - "sustain" can probably be attributed in part to how lossy the combination of cantilevered neck and body are as compared to a "conventional" build. You have characterized the mod as a "charging" of the laminated aluminum structure with an apparent "bloom" of the struck note. If I attempt to put this into somewhat analogous electronic terms then it is akin to the charging of a capacitor in an integrator. There is a charging time constant which attenuates sharp rise times - a fundamental single-pole low-pass filter. Would you suspect that there is a mechanical "time constant" associated with the laminated structure such that is does, indeed, behave as somewhat of a sonic integrator to abrupt and short rise times but is still "charged" by repetitive cycles of the other frequencies of interest? This might very well be accomplished in just a few milliseconds - a time period not necessarily noticeable without actually measuring it or attempting to calibrate your ear. There goes your attack signal - relatively unnoticed although quite real. I might hazard a wild guess that part of this is masked by the apparent additive effect during the "blooming" period and which I assume to be immediately following the picking transient. These are just semi-educated guesses but prime fodder for an in-depth investigation. It would be a nice challenge to compare the two instruments on a test bench. Validation of such an endeavor is justified since the structures are quite dissimilar - quite different from comparing the unmodded Dekley to the GFI and looking for miniscule differences as opposed to what one assumes will be glaring aberrations 'twixt the other two. It'd be a ton of fun.

And the beat goes on.

Richard
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Georg
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Re: outer "current coil" effect at play..?

Post by Georg »

Richard,

New D'Addario and Jagwire strings ;) The 12th fret harmonics is good and clear, but sounds "rounded" (too sinusoidal compared to on my other PSGs) as if there are no overlayered higher harmonics. D'Addario strings "chime" slightly brighter at 12th fret than Jagwire LGs.


Regardless of string types sustain is quite good and even to above 24th fret, but triggering harmonics 12 frets up from anywhere is especially difficult on the modded Dekley compared to on my others, and they always sound "rounded".

No problem making the fundamental tone sound "chimy" the way I pick - light, but the peak-level doesn't rise nearly as much as on my other PSGs when I pick harder.

The loudness curve has been engraved somewhere in the back of my brain since I built my first amps, receivers etc at the age of 10, so no confusion (or tired ears) caused by varying base-levels and frequency-sensitivity here - I compensate mentally and not by turning knobs.
By myself I play at levels that don't require me to raise my voice to be heard, and I have a low voice. So, apart from that I have experienced inner ear problems after plane flights that have impaired my hearing (and playing) considerably in periods - something Bent know about from my visit at his place, my hearing and ability to analyze complex sound is well balanced and good for my age.

There is a mechanical time-constant in the construction, a few hundred milliseconds delay before the entire construction "plays" - vibrates - along, and I have contributed most of the attenuated attack, amount/level of harmonics and increased sustain to the mechanics - at least up until now.

I am just starting to wonder if some of the attenuated attack and reduced amount/level of harmonics can/should be contributed to electrical phenomenons in the construction. If so I will have to take them into account for my new project.
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Pat Comeau
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Re: outer "current coil" effect at play..?

Post by Pat Comeau »

Georg, do you have any audio clips of your modded Dekley?, one ear is different from another :P .

Pat :)
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Georg
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Re: outer "current coil" effect at play..?

Post by Georg »

No audio clips of any of them. Those I have on videocamera with "automatic audio" don't count.
richard37066
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Re: outer "current coil" effect at play..?

Post by richard37066 »

Georg -

I'm tossin' things up into the air again.

Are you expecting too much from a humbucker? A single coil has that resonant peak just before falling off at a rate of 12db/octave. The location of the peak (and the "bandwidth") can be altered greatly by whatever capacitance is added in parallel to the coil by way of cables, etc.. The humbucker generally does not have that peak but is more or less rounded as it falls into an 18db/octave (?) slope. It is not affected, by and large, by added capacitance. IF - the pickup, itself, is the prime culprit then the rolloff of high frequencies will leave an essentially sinusoidal signal at the high end. One must not discount the position on the strings at which a barred note is plucked.

What is the distance of the center of the pickup to the center of the changer finger? Small changes in this dimension (among other things) can have a marked effect upon the number of higher harmonics detected. I have suggested to Ed Packard that I may investigate this at some point in an effort to find a "baseline" tone to my liking which then would require minimal EQ-ing afterwards. Got my fingers firmly crossed on that one. Although most manufacturers have more or less settled upon a "standard" distance of approximately 2", the fact that the pickup is locked into a "well" in the aluminum neck precludes the possibility of adjustment in this regard. Not discounting Ed's electronic version of the pickup (which, by the way, is SKINNY), the Lace Alumitone is thin enough to slide back and forth under the strings if one cannibalizes the unit by lopping off the mounting ears. To my tastes, the Alumitone puts the GFI II to shame in the basic tone department. Single coil - in a convoluted sense - versus the humbucker, once again. I may just get my brave streak going and hack away at the Alumitone that I now have on my E9 neck. I shudder at the thought but, as the man says, nothing ventured, nothing gained.

Tinker away, my friend. The answer is just around the corner.

Richard
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Georg
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Re: outer "current coil" effect at play..?

Post by Georg »

Richard,

Of course I kept distances relative to bridge and strings the same when I fixed the PU above the strings. Testing would not make much sense otherwise. Didn't loosen the original cable either, so all down the chain was unchanged as I "turned it over". 1 meter of "super-cable" before the load - a BOSS LMB-3, which is my normal set-up.

The humbucker on my modded Dekley is movable - approx 20 mm lengthwise. See the enlarged opening in the neck for the PU on the picture - it is in "bridge-position" in that picture. The PU isn't fixed with screws or anything, as a rubber-ring around it holds it on top of the neck and only the strings prevents it from falling out during transportation.
So, I have tested all that can be tested regarding PU position for/with the George L on the modded Dekley over the last 18 years or so, and it replaced the original PU in the same, un-modded, Dekley 5 years before that.


The movable/sliding PU is an interesting concept, and I use it as a very effective "tone-control" on the modded Dekley. Going seamlessly from "round" to "sharp" on the PSG itself, is practical. I have found the "normal" distance from bridge to sound well balanced - almost max distance on mine, so unless you want the "tone-control" there probably isn't much to gain on sliding the PU.

I would not butcher an Alumitone in any way. I have checked that mine will fit tightly in the modded Dekley (with insulation sheets on the sides) and remain lengthwise movable. I just haven't found the incentive to replace the quite good-sounding George L humbucker so far.


If there's a "coil surrounding a coil" effect created by the PU cavity in the solid aluminum neck, it is likely to be zero or not noticeable with the Alumitone. Will have to cross-check on some of my other PSGs with regular necks to make sure I am not looking for "ghosts" ... some day when I find the necessary incentive 8-)

Thanks for all input.
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Re: outer "current coil" effect at play..?

Post by richard37066 »

Georg -

All Right!

It has been difficult to discern what that dark "shadow" was in the photos on your instrument. Now I know! Lay it on me - within the limitations of your expanded cavity, have you been able to approach a condition where your personal tonal tastes are closely realized? You seem to be satisfied with the resultant range of tone and that is precisely what I am looking for - a range within which I might find a personal "sweet spot". And, yes, I am looking for a "mechanical tone control" beyond which I need only use a modicum of EQ in order to satisfy my own personal tastes.

Educate me, my friend! I'm all ears (eyes)!

Richard
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