Thanks for that - I know nothing about RF duplexers!
This is what I suspect, based on the fact that the distributed stray capacitance of the pickup winding only seems to have an effect on frequencies above the range of the electric guitar and it's speaker.
The thick brass(?) housing around the OEM humbucker in one of my South Korean guitars, on the other hand, seems to have a very audible effect. One massive shorted turn...
Here is a thread in which some people say they can hear a difference between a copper-plated nickel humbucker cover, and one that's not plated: Nickel Pickup Cover Material
-Gnobuddy
I have never tried to wind a conventional guitar pickup. Most of my experiments have been related to individual pickup coils per string, and have not been too successful, but I did get some more material for further experimentation down the road.
I went off on a photoelectric pickup tangent several years ago, with promising results......that all ended with the advent, and subsequent popularity of LED lighting. Much of that stuff is filled with high frequency modulation from the cheap, poorly filtered SMPS based power supplies.
Besides the usual MIDI aspects of hex pickups, there is still one aspect of the electric guitar world that remains unexplored. We all have heard the muddy ugly sound that results from playing full six string chords through a highly distorted amp. This comes from the non musically related tones created by the IMD products generated when two or more simultaneous signals are stuffed through a non linear device, like an amp turned up to 11.
It should be possible to route the output of each string through it's own individual amp, and speaker. Each amp could have it's own controls and speaker tailored to the frequency range it produces.
Many years ago I cut a couple single coil pickups up, and rewound them to be two separate single coil pickups each fed to their own amp. This was a step in the right direction, and afforded far more tone variations than the usual setup, but IMD was still a problem when fully cranked. One amp per string would generate zero IMD in theory since it only sees one tone at a time.
I have a piezoelectric hex pickup and some experiments with it show promise, but I prefer the sound of magnetics, or a blend of the two.
Note that some of the cheap little PC "beep" speakers are actually magnetic, and do make a fair single string pickup, albeit with a rather low output, requiring an opamp in the guitar, as does the piezo pickup, due to it's high output impedance.
I imagine a full hexaphonic system would have so many controls (like a modular synth) that it would be hard to master, and harder to play live without some kind of preset store and recall setup.
This was the reason behind my diversion into solid state guitar amp stuff in the 1990's using some SPI controllable tone, volume, and graphic EQ chips....neat idea, but it didn't catch on and the chips have since gone extinct.
I went off on a photoelectric pickup tangent several years ago, with promising results......that all ended with the advent, and subsequent popularity of LED lighting. Much of that stuff is filled with high frequency modulation from the cheap, poorly filtered SMPS based power supplies.
Besides the usual MIDI aspects of hex pickups, there is still one aspect of the electric guitar world that remains unexplored. We all have heard the muddy ugly sound that results from playing full six string chords through a highly distorted amp. This comes from the non musically related tones created by the IMD products generated when two or more simultaneous signals are stuffed through a non linear device, like an amp turned up to 11.
It should be possible to route the output of each string through it's own individual amp, and speaker. Each amp could have it's own controls and speaker tailored to the frequency range it produces.
Many years ago I cut a couple single coil pickups up, and rewound them to be two separate single coil pickups each fed to their own amp. This was a step in the right direction, and afforded far more tone variations than the usual setup, but IMD was still a problem when fully cranked. One amp per string would generate zero IMD in theory since it only sees one tone at a time.
I have a piezoelectric hex pickup and some experiments with it show promise, but I prefer the sound of magnetics, or a blend of the two.
Note that some of the cheap little PC "beep" speakers are actually magnetic, and do make a fair single string pickup, albeit with a rather low output, requiring an opamp in the guitar, as does the piezo pickup, due to it's high output impedance.
I imagine a full hexaphonic system would have so many controls (like a modular synth) that it would be hard to master, and harder to play live without some kind of preset store and recall setup.
This was the reason behind my diversion into solid state guitar amp stuff in the 1990's using some SPI controllable tone, volume, and graphic EQ chips....neat idea, but it didn't catch on and the chips have since gone extinct.
In the 1990s I experimented with an optical pickup too (something I was already using in grad school to measure vibrations of a mirror suspended in a vacuum tank). But I had issues with shot noise, as well as fluorescent room-lighting flicker at 120 Hz. String-bending on the guitar was a problem too, as full-note bends would push a string entirely out of the light beam. So I gave up on the optical pickup idea.
I tried a brief experiment with a home-brew six-coil pickup in the late 1980s. I had no money at all, so I used a 4069 CMOS hex inverter for my six-channel preamp, biasing all the inverters into linear operation with a resistor connected from input to output. It worked, but badly, with lots of hiss. I never followed up that idea later.
I have a Boss DA-2 distortion pedal. One of the advertised features is that you can play heavily distorted chords and retain some clarity. It's a digital pedal, and I think it uses DSP to, in effect, separate out each of the six guitar notes (probably with an FFT), distort each one individually, and put them back together.
Craig Anderton's "Quadrafuzz" used a similar idea, separating the guitar signal into four frequency bands with analogue bandpass filters, then distorting each band individually before recombining the signals: PAiA: Quadrafuzz Design Analysis by Craig Anderton
-Gnobuddy
I tried a brief experiment with a home-brew six-coil pickup in the late 1980s. I had no money at all, so I used a 4069 CMOS hex inverter for my six-channel preamp, biasing all the inverters into linear operation with a resistor connected from input to output. It worked, but badly, with lots of hiss. I never followed up that idea later.
I have a Boss DA-2 distortion pedal. One of the advertised features is that you can play heavily distorted chords and retain some clarity. It's a digital pedal, and I think it uses DSP to, in effect, separate out each of the six guitar notes (probably with an FFT), distort each one individually, and put them back together.
Craig Anderton's "Quadrafuzz" used a similar idea, separating the guitar signal into four frequency bands with analogue bandpass filters, then distorting each band individually before recombining the signals: PAiA: Quadrafuzz Design Analysis by Craig Anderton
-Gnobuddy
I made a simple led / photocell setup which sucked for the same reason you mentioned, especially 60 and 120 Hz pickup. All of it was mounted near the bridge, and covered with a large bridge cover from an old guitar.
The next step was infrared led / sensor pair from TV remote control systems, better, but not perfect.
The next step was using a high frequency square wave lighting two LED's out of phase, and synchronously chopping and alternately reversing the sensor output such that low frequency stuff cancelled out. That worked pretty good until high frequency light noise from LED lights appeared.
I did not know that PAiA was still around. My first "modular synth" was a PAiA 2720 kit with shirt buttons for keys back in the early 70's. I got a keyboard out of a dead organ in the trash dump and wired it up. Neat toy, but wouldn't stay in tune for very long.
For now I'll play some more with the magnetic stuff. I need some good weather for some wood working time......I got another Dumm Blonde idea for a guitar with swappable / removable pickups and electronics. It would make experiments like these far easier and I wouldn't need to toss the guitar body when I change my mind, add or remove some controls, or something just doesn't work.
I learned it by watching this guy:
YouTube
The next step was infrared led / sensor pair from TV remote control systems, better, but not perfect.
The next step was using a high frequency square wave lighting two LED's out of phase, and synchronously chopping and alternately reversing the sensor output such that low frequency stuff cancelled out. That worked pretty good until high frequency light noise from LED lights appeared.
I did not know that PAiA was still around. My first "modular synth" was a PAiA 2720 kit with shirt buttons for keys back in the early 70's. I got a keyboard out of a dead organ in the trash dump and wired it up. Neat toy, but wouldn't stay in tune for very long.
For now I'll play some more with the magnetic stuff. I need some good weather for some wood working time......I got another Dumm Blonde idea for a guitar with swappable / removable pickups and electronics. It would make experiments like these far easier and I wouldn't need to toss the guitar body when I change my mind, add or remove some controls, or something just doesn't work.
I learned it by watching this guy:
YouTube
Cool trick! Reminds me of the optical choppers and lock-in amplifiers I used to work with.
Amazing, isn't it? These days even this this diyAudio sub-forum seems almost dead, and somehow PAiA soldiers on. My hat is off to the people running it!
Cool idea!
You might like this version of that concept - pickups that rotate in and out of place! YouTube
The crazy internal mechanical linkage (to the slide switches) looks too complex to home-brew well, but the rotating cylinder carrying the pickups seems do-able; flipping the pickup cylinder over with a finger would still be pretty quick and easy.
Way back in 2014 or so, Fender tried a much simpler version of the "quick sound change" idea - they sold a Stratocaster with separate "personality cards" that you could swap in or out to instantly re-wire the existing pickups, switches, and knobs. I don't think the idea caught on, but perhaps it might inspire you: YouTube
-Gnobuddy
I borrowed the idea from some Hewlett Packard and Boonton RF measuring test equipment. The Boonton measured millivolts of RF signals in the presence of large 60 HZ noise in an industrial setting. It used a mechanical chopper. I was changing those choppers at a 1 to 3 a month rate for over $100 each in the 1970's since the equipment ran 24/7.
The HP RF power meter did pretty much the same thing with some CMOS switches. One of my tasks was to copy the HP circuit, put it on a little board and use it in the Boonton to replace the mechanical chopper.
The Gyrock system is probably beyond my construction skill level, and I am more interested in experimenting with active electronics in the guitar than the pickups. Previously I had to remove all the strings to take the pick guard out which had the electronics on it. The cycle time from playing, disassembly, reassembly, to playing again was a couple hours if I didn't screw anything up, or lose my patience.
I am going to try a mount from the back approach for faster swaps. Since many of my dumb guitar ideas wind up in the trash, it will be ugly pine wood. It will serve as a test bed to try out dumb ideas that have been stuck in my brain since the 60's and 70's.
Here is another that I have experimented with off an on since my first day at Motorola in 1973 when I first met the Motorola Vibrasender and Vibrasponder (essentially the same thing).
Here are two pictures of a device that Motorola used to detect or generate fixed audio tones used for electronic signaling in two way radios. Larger versions were used back into the late 1930's. These are from the last generation in the 60's and 70's before an opamp based chip replaced them.
Inside you see a mechanical vibrating reed with two tiny magnets glued on the end that moves. There are two coils, one near each magnet. To me this looked just like the reed used in a Wurlitzer piano, so I spent some time playing with these and expanding on that idea.
In "sponder" mode an audio signal is sent to one coil, and the other coil goes to a level detector. When the audio signal is at the "wrong" frequency, nothing happens. When the input frequency is very close to the resonant frequency of the reed, it will vibrate, and the moving magnet will induce a voltage in the other coil, tripping the level detector.
In "sender" mode there is no level detector. The signal from the output coil is amplified and fed back to the input coil creating an oscillator, to generate the tone.
There was a bank of Vibrasenders in the dispatchers office, and a unique Vibrasponder in each taxi's radio so one radio could be individually called.
So the Dumm Blonde One wires one of these to a guitar cord and smacks it with a drum stick, and music was made. Then he learns how to take them apart and "tune" them to musical note frequencies with some well placed solder. He might have spent days experimenting with the coils out of these things and a guitar string stretched out on a 2X4. Maybe even mounted a few inside a kids toy piano.
The Vibrasponders came in two flavors, most were used in "subaudible" (low frequency) signaling, such that signaling and voice could be sent at the same time. The lowest available frequency was 67 Hz and the highest was around 200 Hz. The coils from these did not respond well to the higher notes on a guitar string. There was a much smaller Vibrasponder with frequencies from 1Khz to 2.something Khz used in pagers, but their tiny internals were too easily damaged for many successful experiments.
Once the idea was planted, it didn't take much for me to swap out the Vibrasponder coils for guitar pickups. Yes, it's possible to take two pickups and a healthy opamp and make a guitar string play itself. Hours of fascination ensued from 6 strings mounted on a 2X4, tuned to an open E chord, and a Coricidin bottle.
This the principle behind the "infinite sustain" systems seen today. My experiments at the time (early 70's) were done with a pair of plastic housed unshielded pickups from an old Hagstrom. I still have them. There was a very narrow range of feedback gain where a self sustaining string happened, and before utter mayhem broke out. This could be improved with shielding between the two pickups. Things might have worked out better with grounded metal cased pickups. Attempting to make all 6 strings play nice through two pickups creates all sorts of unwanted tones where harmonics of the bass strings tend to excite higher strings.
I want to explore a separate sustainer for each string, hence the hex pickups.
The popular Ebow works the same way with two metal rails on either side of the target string, with a coil mounted on each rail.
Attachments
Couldn't agree more!John Mayer is one of my guitar gods as well. What you perceive as John Mayer sound is
95% John Mayer
5% guitar, pickup, strings - the hole rig
So why waste your time with the most unimportant area?
Another example: If you didn't know, would you have guessed that Jimmy Page recorded any guitar track (with the exception of the acoustic ones and the lap steel, of course) for the 1st Led Zeppelin album using a simple Telecaster that he has been given by Jeff Beck previously?
Best regards!
@ Gnobuddy
I have an possible explanation for your observations when using a brass pick up cover.
Brass is very good at reducing magnetic flux/inductance (perhaps leakage inductance in particular?)
I guess it acts almost as an air gap does in a transformer core, lower magnetic permeability I think, perhaps then this shifts the flux pattern around the strings.
Sorry for the OT.
I still want to know why I prefer nickel strings over steel, I've tried many strings and always end up coming back to Slinkys, on all my guitars.
String composition has probably just as much influence on tone, though I dont understand why!
I have an possible explanation for your observations when using a brass pick up cover.
Brass is very good at reducing magnetic flux/inductance (perhaps leakage inductance in particular?)
I guess it acts almost as an air gap does in a transformer core, lower magnetic permeability I think, perhaps then this shifts the flux pattern around the strings.
Sorry for the OT.
I still want to know why I prefer nickel strings over steel, I've tried many strings and always end up coming back to Slinkys, on all my guitars.
String composition has probably just as much influence on tone, though I dont understand why!
It's interesting to look at the design of the Filtertron humbucker cover (image attached). The metal right around the pole-pieces is cut away, and there's also a gap cut in the metal so that eddy currents can't flow in a big loop that encloses all six pole-pieces.
Clearly, the designer of the Filtertron was thinking about eddy current losses in the cover more than his counterpart at Gibson did.
-Gnobuddy
Attachments
What guitar uses those?
They remind me of a Burns, only humbucking.
Eddy currents must have some impact, is it the only cause?
I guess it depends how the PUPs are constructed.
Usually a single ceramic bar and 6 pole pieces.
All the flux linkage is through the magnet itself, until a ferromagnetic plate is put in front of it.
A brass plate may be better, as non magnetic, but eddy currents still exist.
Now if you were to put a 0.005" brass shim behind a pole piece....I guess you could weaken the field intentionally...If that is a good idea (I dont know)
Right now I have a spare set of strings lay about for my LP smartwood, which could only be more awesome if it had chrome hardware, not gold.
They're EB Hybrid Slinky, usually I'll get these or Heavy Bottom Skinny Top (or is it STHB?). Super slinky were my go to string on my first guitar, a Strat clone, and they give a nice woody bass tone.
I just need some weight in bottom end, dropping to D, or CDAGBE, and after a week or so they start sounding rubbery. So the Strat is the only one that gets Slinkys now, the Trem is completely trashed, ant the guitar needs a refret/serious fret levelling and hard tail conversion.
The LP is a Gibson and has the normal PUP covers, sounds great, but I havent tried to take them off! I have a Vintage SG clone, with the same style PUPs and it sounds more vintage lower output and less growl.
I was never that good a solo player, but bending a 9 1.5 steps isnt too bad, 2 steps is more difficult.
My band mate used to laugh at my attempts performing Cockerel Rock 80s Hair Metal guitar solos when I briefly changed to an 8 high E, I just ended up doing bend vibrato around a step, floyd rose tremelo style, with a cheap strat. Broke strings more often than I changed my underwear if I recall. So I just settle for a 9 E. I'm just too hamfisted!
They remind me of a Burns, only humbucking.
Eddy currents must have some impact, is it the only cause?
I guess it depends how the PUPs are constructed.
Usually a single ceramic bar and 6 pole pieces.
All the flux linkage is through the magnet itself, until a ferromagnetic plate is put in front of it.
A brass plate may be better, as non magnetic, but eddy currents still exist.
Now if you were to put a 0.005" brass shim behind a pole piece....I guess you could weaken the field intentionally...If that is a good idea (I dont know)
Right now I have a spare set of strings lay about for my LP smartwood, which could only be more awesome if it had chrome hardware, not gold.
They're EB Hybrid Slinky, usually I'll get these or Heavy Bottom Skinny Top (or is it STHB?). Super slinky were my go to string on my first guitar, a Strat clone, and they give a nice woody bass tone.
I just need some weight in bottom end, dropping to D, or CDAGBE, and after a week or so they start sounding rubbery. So the Strat is the only one that gets Slinkys now, the Trem is completely trashed, ant the guitar needs a refret/serious fret levelling and hard tail conversion.
The LP is a Gibson and has the normal PUP covers, sounds great, but I havent tried to take them off! I have a Vintage SG clone, with the same style PUPs and it sounds more vintage lower output and less growl.
I was never that good a solo player, but bending a 9 1.5 steps isnt too bad, 2 steps is more difficult.
My band mate used to laugh at my attempts performing Cockerel Rock 80s Hair Metal guitar solos when I briefly changed to an 8 high E, I just ended up doing bend vibrato around a step, floyd rose tremelo style, with a cheap strat. Broke strings more often than I changed my underwear if I recall. So I just settle for a 9 E. I'm just too hamfisted!
Last edited:
Some Gretsch guitars come with them (Filtertron pickups). I don't own any Gretschs, but I think it's interesting to see how different engineers tackled the same problems. Gibson and Fender didn't always come up with the best solutions.
Speaking of Fender, Leo seems to have stolen "his" pickup design wholesale from the one invented by John De Armond, and sold by his older brother, Harold De Armond - six Alnico magnets serving double-duty as pole pieces, pushed into a slender elliptical bobbin wound with a single coil of #42 gauge copper wire: The Pickup Story, Part II: De Armond Guitar Microphones )
Alnico conducts electricity, but poorly - it has a rather high resistivity (about 70e-8 ohm metres) compared to, say, copper (1.7e-8 ohm metres). So eddy currents can barely flow in Alnico pole-pieces, which reduces high frequency losses, which is probably one reason why De Armond's pickup design produces those bright sparkly trebles everybody expects from most Fender guitars.
Dunno if it's the only cause, but in the case of the thick brass pickup covers, I think it's a major one.
Maxwell's equations tell us that eddy currents increase with frequency (the dB/dt in Faraday's law of induction), so eddy currents do tend to affect high frequencies most. These currents decrease if the material is a good conductor (low resistivity), and also increase if the material is thicker (low resistance). So thick brass is a pretty bad choice.
Gibson humbucker pole-pieces are ordinary steel screws (conductivity about 12e-8 ohm-metres), so they're more prone to eddy current loss than Alnico pole-pieces. Add in more inductance from the two coils (instead of one), and finally plop a conductive metal shell over the whole thing, and you can see why Gibson's humbuckers would be less bright-sounding than De Armond's pickup design as used by Fender.
To complete the full magnetic circuit, the flux also has to go through the pole-pieces in the coils, and the guitar strings hovering just above them, and the little air gaps between pole-piece tips and guitar strings.
I think of these electromagnetic guitar pickups as variable-reluctance magnetic circuits - when the string vibrates and changes the air-gap to the tip of the pole-piece, the reluctance of the magnetic circuit fluctuates, and so the amount of magnetic flux fluctuates, and so the coil generates an EMF, just as Faraday said it would nearly two hundred years ago. Pretty much exactly the way a moving-iron microphone worked, with guitar strings replacing the magnetic microphone diaphragm.
I don't see terms like "reluctance" and "magnetic circuit" used in modern books on magnetism, only in older ones, but I think they make it much easier to visualize what's happening, as we can use our understanding of Ohm's law and electrical circuits to visualize what's happening in a magnetic circuit. More reluctance, less flux. Less reluctance, more flux. Just like a varying resistor in an electrical circuit!
I have one guitar with gold hardware. It looks awful after ten years, pitted and stained and ugly. Never again!
I'm guessing Gibson makes those covers out of much thinner material than the ones in my South Korean guitar, or maybe Gibson used a material other than brass, with higher resistivity, and lower eddy current losses. Stainless steel would probably be pretty good, except you can't stamp it out with a die and a press!
The guitar I was talking about - an Agile AS-820, probably made by Cort, and definitely, erm, inspired by a Gibson ES-335 - has quite thick brass PUP covers. The pickups weighed a tonne when I pulled them out - there's lots of heavy brass there!
I play both acoustic and electric guitar. Acoustic guitars have a longer scale length, a higher action, and tend to use much heavier-gauge strings, so the more acoustic guitar I play, the heavier my left hand gets.
I put 10-gauge strings on my acoustic (most acoustic players use 12 gauge), and even so, 10-gauge strings on my Les Paul copy feel too floppy (because of the shorter scale length). I have a tendency to pull some notes in a chord slightly out of tune on the Les Paul and 335-type guitars unless I consciously use a light touch with my left hand.
11-gauge strings seem to feel about right on a Les Paul scale length, but that will change quickly if I stop playing acoustic guitar for a month!
-Gnobuddy
There is no Agile guitar factory. Welcome to the world of sub-contracted manufacturing!
Yes, I bought my Agiles (I have a few) from Kurt Zentmaier of Rondo Music, who has them manufactured by a large South Korean guitar manufacturer to his specifications. Most likely he picks choices for woods, tuners, hardware, etc out of a list offered by the manufacturer, the only truly custom part being the trademark Agile headstock shape.
Just one or two large South Korean manufacturers build guitars for many other brands sold in North America (LTD, Jackson, Dean, Hamer, Epiphone, Fender, Ibanez, Yamaha, Schecter...). These brands don't have their own factories there - that would be prohibitively expensive. Instead, they sub-contract one of the South Korean factories to do a run of guitars for them. The same factory might build, say, Jacksons one day, and Deans the next, and Epiphones the day after that.
It's not 100% clear exactly which large South Korean manufacturer makes guitars for Kurt. It is most likely either Cort or Samick.
The important thing isn't where the guitars are made, or by whom. It's how the guitars are made. And my experience is that all the Agiles are well made, all are great bang for the buck, and some are really excellent guitars straight from Rondo.
IMO, the only weak point is the OEM pickups in some models. My AS-820 always sounded dull with the stock pickups, no matter what I did. I recently replaced them with a pair of Seymour Duncans, and that has transformed the guitar's sound. It was a tedious job, fishing all the bits and pieces through the f-holes, but well worth it in the end.
-Gnobuddy
True. I'm not on any of the guitar forums any more. I tried a few when I got back into music around 2009, but I felt the main focus on the guitar forums really wasn't about music or learning how to be a better musician.
Rather, the majority of posts and threads were about buying stuff, showing off the stuff you had, asking what stuff to buy next, and maybe putting down the other guy's stuff because it wasn't as special as your own stuff.
This wasn't really what I was looking for, so I stopped being active on any of the guitar forums.
These days I find I have plenty I can learn by working through one of Justin Timbercoe's video lessons on You Tube, or watching Danish Pete play on the Anderton's Music channel, or from videos of other inspiringly good musicians.
-Gnobuddy
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.