Okay, the funky gold foil pickups found in cheapo Japanese and American gutiars in the 1950s and ’60s are popular again. And trend slut that I am, I’m smitten with them. But they do this one really weird thing ….
It has to do with the capacitive relationship between the guitar volume knob, pickups, and downstream pedals and amps. If you don’t use your guitar’s volume knob as an expressive device, this behavior probably doesn’t matter. But if you do, this is potentially a big deal, one worth considering before purchasing a pair of gold foils.
I first realized this as I was preparing my Gore Pedals demo for the NAMM show. Many of my pedal designs depend on the ability to alter tones from the guitar — it’s how I get away with using relatively few knobs. It’s the quality you hear in the first minute of my Cult pedal demo:
You just can’t do that with gold foils. Apparently, the rubber magnets in gold foil have a different capacitive relationship with downstream gear, relative to conventional alnico- and ceramic-magnet pickups. Some of the peaky, high-resonance sound you get when rolling back the volume knob on a guitar with gold foils are pretty cool, and I can certainly imagine using them. But I definitely have to modify my technique when using gold foils.
I recently reviewed one of the bitchin’ new Supro guitars for Premier Guitar. Their pickups are based on a different historic gold foil model, but they exhibit the exact behavior demoed in my first video above. After writing that review I spoke with Ken Calvet of Roadhouse Pickups, who created the excellent-sounding Valco-style gold foils for Supro. He acknowledged the unusual volume knob behavior and attributed it to the rubber magnets used in historically accurate gold foils.
My first video above demonstrates this property using a capacitance-dependent vintage-style Fuzz Face. Not only do you encounter the same thing with many non-buffered (i.e., cool) fuzzes and boosters, but also when plugging directly into an overdriven amp. You can’t summon clean sounds from a dirty amp via the guitar volume knob the way you can with most conventional passive pickups.
But despite all of that, I’m still crazy for the Lollar Gold Foils in my DIY Resistocaster:
Has anyone else noticed this quirky characteristic?
Huh! I tested this on my Gold Foil-equipped Partscaster – & you’re completely right! I do use my volume knob expressively often – especially because I use a Fuzz Face as a significant part of my pedalboard, which I’ve found is really built for this approach (Sam McCrae actually instructed me to dime the FF & adjust the amount of distorted tone with the volume knob. However, I apparently do this more on my P-90-equipped guitars (where the cleans are sweet & ringing). On the Partscaster, I don’t think I ever noticed because the Gold Foil there is on the neck, where if I engage usually have/want a higher-gain, non-clean situation going. (I had played Teiscos with original GFs but didn’t play clean ever – I get too garagiste excited!) My other, non-installed GF (a Lollar) is going on a neck as well. Useful!
So I’m not crazy! I had the experience, though not with a FF, but with my Cult pedal, which like the FF, relies on the capacitive relationship between guitar and amp. FWIW, I second Sam McCrae’s method 100%. It just doesn’t work very well with these pickups. (Though the full-on FF distortion is pretty epic with gold foils.)
Actually meant to include a shot of my guitar, not pedalboard…
That’s okay. Everyone likes red! 🙂
I hope someone can explain more than “rubber magnets” because I find this behavior baffling.
I think about guitar circuits in terms of impedance – which generally means that if something is inductive or capacitive then impedance changes with frequency. If you have an inductance and a capacitance interacting directly, you get a peak. Resistance is the case of an impedance which does not change with frequency. They are both measured in ohms. Other than that there is not much to say!
An impedance which is low tends to load down a connected impedance which is high, whereas as high impedance has relatively little effect on a connected low impedance. This is more about pickup impedance than normal people can handle: https://courses.physics.illinois.edu/phys406/Lab_Handouts/Electric_Guitar_Pickup_Measurements.pdf
So what the *&@#$(!$*& is the model for a gold foil pickup? If it has measurable DC resistance then it is not a series capacitance (e.g. a piezo pickup).
A guitar volume control’s fixed part hangs off the end of the pickup. If you have a low impedance hanging off the adjustable wiper, then the load on the pickup itself will be maximum when volume is cranked. When volume is low then the pickup itself is less loaded. Whether the pickup impedance is low or high, I would not expect this behavior.
Joe are you aware of any patent drawings about these showing what the “gold foil” itself does or where it is structurally?
Does it only happen when you use it with a heavy load e.g. grounded emitter input with capacitor to base? Or does it also happen when you use it with a high impedance buffer or effect?
Hah! I was hoping YOU would explain it for everyone, man! I am utterly stumped. But it’s 100% repeatable, and lots of folks have chimed in here and on my YouTube channel seconding the observation. I’ll plug in a buffer and see what happens …
I’m a little hesitant to make pronouncements here after blowing lots of theoretical BS smoke over the years, the kind that I instantly regret. Even though I was using the best words!
It’s better just to ask questions and act confused, because I am. Terry’s description is nice but it doesn’t help me too much. I do like the tone of those pickups however!
I’m pretty sure the ‘capacitance’ of the magnet has nothing to do with it. The construction of a Gold Foil pickup is broadly like any other electromagnetic guitar pickup – a coil of copper wire and a magnet.
A Gold Foil pickup of the Teisco/Lollar type has a fairly wide flat coil of 44awg insulated copper wire with the ‘rubber’ magnet in the middle. This sits on top of a metal plate (I believe it is a nickel plated steel plate) which extends past the coil on one long edge and has a fold in it. Like a Strat saddle this fold or crease is drilled and tapped for six small steel screws. Several commentators have said that these pole screws have no effect on the pickup and are purely cosmetic. While may be true that they do not allow much in the way of string to string output balancing, they are made of a magnetic material and are next to the pickup magnet so I suspect they do influence the output of the pickup. The pickups have metal base plates and top covers. I do not know what these are made of, probably plated brass or maybe nickel.
Alnico magnets and steel poles are electrically conductive so induced eddy currents can flow through them, they also have a magnetic permeability which is greater than that of free space (air). So when inserted in a coil the inductance of the coil goes up. As far as I understand it because both ceramic and ‘rubber’ magnets consist of powdered magnet particles embedded in clay or plastic, they both have low eddy current losses and a low permeability. This would mean that a Gold Foil should have a relatively low inductance and measurements of the Lollar Gold foils show that it is on the low side, around 1.9H (typical Strat single coils are 3H and above).
The Gold Foil has a low flat coil with not a great number of turns so you would expect the COIL to have low capacitance and combined with the low inductance that should mean a low Q. Measured Q at 1000Hz is indeed quite low, 1.3 compared to 2.5 to 3 or so for a typical Strat single coil.
With a typical Strat pickup the inductance of the pickup, combined mostly with the capacitance of the instrument cable (into a 1Meg load) results in a resonant peak of at least 3 or 4db at around 4kHz with the volume at max. As you turn the volume down this peak reduces. You wont get such a pronounced peak with a Gold Foil and the response won’t change much as you dial down.
When plugged in to a Fuzz Face or similar then any guitar / pickup is heavily loaded by the low impedance of the Fuzz Face input.
I have recently fitted a Lollar Gold Foil to a clients Telecaster. I did wonder if Gold Foils had a ‘preferred’ control resistance and tone capacitor value. A quick internet search yielded nothing conclusive, other than the possibility that the old Teisco guitars may have used 100K controls. I fitted the pickup with the existing 250K controls and 0.022uF tone cap and I did notice that the tone control didn’t have much effect on the Gold Foil and I only started to get a little treble roll off at the extreme anti-clockwise of the tone control.
Terry = my hero.
Thanks for so much interesting detail. (And fair warning: I have another video coming in the next few days featuring a different historic pickup with its own set of oddball behaviors.)
Interesting about the tone caps. I never even checked that out on my guitar, ’cause I used a ToneStyler for top cut, and a 3-position bass-cut switch, rather than pots running to ground.
How about this for a theory –
I have simulated the guitar pickup driving a Fuzz Face in LTSpice. With ‘normal tone controls this shows that the gain of the Fuzz Face is greatly dependent on the impedance of the guitars volume control. Gain drops off very rapidly as the control is turned down.
However with a Tonestyler in circuit the resonant peak from the pickup inductance in parallel with the Tonestyler capacitance increases (output at certain frequencies goes up) because the volume control gradually isolates the resonant circuit – pickup inductance in parallel with the Tonestyler capacitance – from loading by the low impedance of the Fuzz Face input.
In effect although the volume control is reducing signal and decreasing the gain of the Fuzz Face, at the same time the output of the pickup is increasing. However it shouldn’t make any difference what the pickup is, this behavior should occur with any pickup.
The original gold foils I’ve seen do have fairly low DCR and used 100k volume pots.
One of the quirks of the gold foils comes via the folded base-plate which I understood to be soft iron and that this loaded down the coil in a way, increasing the inductance. I add the qualification here that electromagnetism baffles me completely, so treat this info gingerly.
The old Epiphone New Yorker pickups are similar. They LOOK like a minihumbucker, but are actually just another single-coil in HB clothing, with the “adjustable screws” very close to the edge of the pickup and contributing very little to the tone or string levels. before I gave it to Mark Knopfler in the late 80’s, I took one apart to see, and it is very similar to the construction of a gold foil, albeit higher quality and a bigger coil.
I have been slowly rewinding a busted original GF with a ceramic magnet. Once I’m done, I’ll have to see if it exhibits this behaviour. But my undereducated guess is that the effect is largely related to the pot value. Someone should try it out with other pot values and see.
Thanks for more smart insights, Mark! I don’t have time this week to swap the pot (’cause I have some work that actually, you know, pays). But I did a quickie experiment, running the output from the guitar’s wide-open A250K pot through an additional A100K in series on breadboard. (It’s not exactly the same thing, I know.) The result was similar: level attenuation about as you expect, but the A100K pot never delivers a clean tone on its way to silence. Tones are cleaner, but not clean, and always with an ugly/farty quaility that few players would enjoy.
Might be worth disconnecting the Tonestyler just to see if it is the resonance peak it introduces.
This is fascinating! I thought I was going nuts – I put a Mojo UK hum-sized gold foil in the bridge position of my main guitar and I LOVE the sound but the volume knob seemed not to be doing what it was supposed to. I’m mostly a picking-dynamics player rather than a knobs player so I’m not super stressed, but it would be nice to have the option… has anyone found a solution?
So Ace, are you, like Joe, talking about your guitars volume control behavior with a Fuzz Face style pedal, or are you saying that in general your volume control doesn’t produce a smooth change in volume with the gold foil pickup?
When not running into a Fuzz Face or similar and with normal guitar wiring, turning down the guitars volume (apart from its intended function of reducing the signal going to the amp) isolates the pickup from the capacitance of your instrument cable. This is audible as a change in the frequency and level of the resonant peak formed by the cable capacitance and the inductance of the pickup. As you back off the volume control this peak rises in frequency and gets smaller. If the peak with the volume at maximum is particularly strong (if you are using a long high capacitance cable) then there can be particularly noticeable change in the sound when you back off the volume just a little from maximum.
Try using a low capacitance / shorter cable or running a short cable into a buffer pedal to minimize this effect.
Although of course you might actually be liking the effect of the lower larger peak produced with volume at max and the capacitance of whatever cable you use.
The change in capacitance between various instrument cable types and lengths is what causes people to say a particular cable has a ‘sound’ of its own. This doesn’t normally apply to guitars with active circuitry. You can pretty much use any kind of cable you like with an active pre-amp equipped guitar (or bass). With the pre-amp isolating the pickups from the cable, the cable has no effect on the sound.
Is this a contributing factor to the tone Blake Mills gets on “If I’m Unworthy”? There sounds to me like there is an unnatural farting out sound that he gets.
Umm.. well I found a YuoTube clip of that track he’s playing for Fender and it sounds to me that he has the bass turned up quite a bit and there is some distortion / clipping going on in the low end, which may even be the loudspeaker/s breaking up. It sounds to me like on certain low notes or combinations of low notes the poor cones are just crying – mercy, just stop, I’ll tell you anything you want to know man.
He is playing finger style and the old thumb can get pretty heavy on those low strings, plus he’s muting and that alone can cause thumping farting sounds on the lows. He also seems to have a string through Supro style pickup in the bridge and may be banging the strings on the sides of the pickup aperture.
In contrast, the pickup pickup resonance peaks I have been talking about are all in the high to high mids range.
Also … I see he is fond of odd ‘farty’ sounds anyway and likes to ‘prepare’ (as in way the avant garde composers used ‘prepared’ piano) his guitars with bits of cardboard wrapped around the strings. He says strips torn from D’Addario string packets give the best tone 😉
Got it- Thanks Terry!
Sorry I’m late to the party. I wonder if perhaps the hysteresis of the rubber magnets is at work. Rubber has it’s own set hysteresis curves related to the expansion and contraction of rubber as well as a magnetic hysteresis. Add to this we are talking about physical actions as well in the rubber magnet. The magnet is attracted to not only the case surrounding pickup but also the strings your belt buckle, mic stand and everything metal. Next this rubber magnet is exposed to movements like the vibrations of the strings, guitar pick, any movement of your body. This may only cause invisible microscopic movements of the rubber magnet is rubber it bends and stretches. But those microscopic movements will effect the pickups tone and in a way that multiplies with more pickups like in the Supro guitar ( I just bought for $399). When I turn on 2 pickups it seems to sound even more Gold Foiled like it’s multiplied somehow. This is just one Matt’s opinion but I’ve been having some interesting ideas I plan to play with at first. Also consider that the windings are around a rubber not metal magnet so the capacitance maybe very different. If a wire is wrapped around the rubber magnet you may get a big change if the rubber acts like a dielectric (the stuff in between the plates of a capacitor). If that dielectric (rubber magnet) has those microscopic movements it may become a sort of tiny condenser mic that’s just my beginning theory.
I recently bought a new Supro Westberry and absolutely love it. I was practicing and getting to know when I realized that the G string at the third fret had no sustain, and the 2nd and 4th strings at the third were fine, unless you bent the note. Crazier yet was that on all three, as you bent the string up and down the note came in and out. Checked frets and all………..the problem completely disappeared when I turned off my EHX Hum Debugger, which had NEVER had that effect on any other guitar in the two years I’ve been using it…………but none of them had gold foils!?!?
I haven’t encountered that issue, but it’s not surprising. And actually, the guy who told me the “rubber magnet pickups are just different” theory is the fellow who designed the very pickups in your guitar.
Well the EHX Debugger is a dynamic digital notch filter and I had read reports of its hum rejection not always being completely ‘transparent’. It could well be that the Gold Foils on that guitar slightly emphasize or deemphasize certain harmonics and the debugger’s algorithm decided to notch that note out.
To say that “rubber magnet pickups are just different” is all a bit vague and doesn’t really explain anything.
Rubber magnets aren’t that different from ceramic magnets. Ceramic magnets are a similar idea – magnetic particles embedded in a medium. In the case of ceramic magnets it’s iron oxide and strontium carbonate fused into a hard ceramic material that’s called Ferrite. For rubber magnets its powdered Ferrite mixed with a rubber or plastic binding material.
And the ‘Gold Foil’ pickups aren’t the only pickups to use rubber magnets to provide the magnetic field. Lace Sensors use rubber magnet sheet.
As far as I know the main difference between ceramic and rubber magnets is that, because rubber magnets use a relatively large amount of non-magnetic binder in their composition in order to remain rubbery, they make quite weak magnets. On the other hand they are often manufactured with quite complex patterns of magnetization.
Pickups designed using rubber magnets would be ‘different’ in as much as they would have a relatively weak magnetic field and (like ceramic) the magnets would have low permeability and not be subject to internal eddy currents.
Just found this thread and thought I’d contribute my own observations. Put an original Teisco gold foil into the neck position of a tele parts guitar. Tone control was useless from a practical standpoint, so my trusted tech just wired the tone pot to the bridge pickup only.
I also noted to wild-and-wooly character of the gold foil, which hit the front end of my amp hard and had an impressive bass presence. I had my tech install the “treble bleed” mod (my tech HATES this name, as it actually sends the bass frequencies to ground, NOT the treble). For me, this is where it’s at. As you roll down the volume, not only does the pickup get quieter, but also “thinner” as the bass frequencies go to ground but the high end is preserved. I have found this extremely useful both clean and with gain devices, as it improves the gold foil’s articulation. You can wind the volume back up for solos or whenever you want that bold, slightly blown-out character the pickup is famous for.
Thanks for sharing that info, Red! I dig the (hehe) treble bleed mod and use it often. But I’ve opened up these damn guitars so many times, for the life of me, I can’t remember whether I have it in the guitar here. I’ll have to check. (And add it if I don’t.)
Hi Red,
Interesting what you say about the tone control, if I understand you correctly you found the standard tone control did not roll off the treble for the gold foil pickup?
I don’t mean to be rude by contradicting you or your tech but if, by the treble bleed mod, you mean the connection of a small value capacitor between the clockwise terminal of a volume pot and its wiper then what it does, as you turn the volume down, is provide a more direct path for the high frequencies to the output, while the lower frequencies are still divided down by the volume control. It is literally bleeding the trebles around the volume control and I cannot see how this can be described as sending the bass frequencies to ground.
I have just received a Lollar gold foil pickup in the poet today and I’m about to fit it to a Fender TC90 Thinline guitar.
OK so I have the Lollar Gold Foil neck pickup installed in a Fender TC90 Thinline. Turns out Fender fitted a slightly odd combination of parts for the controls; a 500K linear for volume, a 500K Log (10% or ‘audio’ curve) and a 33nF tone cap.
Played clean the Gold Foil is doing its thing, which I think I would describe as lots of warm bass tones, with a sheen of airy high presence. It also seems to have a wide dynamic range and is very responsive to picking attack.
I have tried playing it through a Fuzz Face copy I constructed using low gain silicon transistors. With this setup – this guitar, these controls and this pedal, I would say the Gold Foil cleans up as the volume is rolled down pretty much to the same degree as the Seymour Duncan P90 in the bridge position on this guitar.
Electronically, the Lollar Gold is much like an early low wind Strat single coil. So the LC frequency response of the coil combined with the usual passive guitar control components is similar to a low wind Strat pickup. It is also a single coil surrounding a single magnet with the north south axis perpendicular to the strings. I think this orientation of the field and perhaps the lack of induced eddy currents in the non-conductive magnet is responsible for the pickups dynamic response.
On the other hand it has a wider (single) magnet that a Strat pickup and a wider flatter coil. So the sensing ‘window’ extends further along the string than a Strat pickup. As a result the comb filtering effect of harmonic cancellation and reinforcement from that wider window accounts for the warm bass with high presence response of this pickup.
I suspect it may be the unique balance of frequencies from this pickup that accounts for the (not Gore approved) sound produced when trying to achieve a clean/er sound through volume roll off when using a Fuzz Face related distortion pedal.
These at least are my initial thoughts. I used a 3.5 metre Fender cloth covered instrument cable for my testing so far. I don’t actually know what its total capacitance is. I have a Lava Retro-coil cable and a Monster Jazz cable I could try out.
Joe,
What Fuzz face are you using when you play that strat? It sounds amazing. I would like to get one. Thanks
tonefiend by joe gore
1 second ago
It’s this one, made from a kit:
https://buildyourownclone.com/products/esvfuzzpnp.
It sounds at least as good as any Fuzz Face you’ll find, and much better than most. It’s also a great project for someone learning to build for the first time, ’cause it’s relatively easy and has great instructions. If you aren’t interesting in making your own, this one is real good:
https://buildyourownclone.com/products/esvfuzzpnp.
You can spend a lot more on a Fuzz Face, but I recommend you don’t. These two sounds as good as anything. Whatever you do, get one with germanium transistors instead of silicon
ones. The silicon ones don’t sound bad, necessarily, but their tone is very different from what you hear here. I hope that helps! :)
Will the lollar gold foil fit the same routing hole as a soap bar p90 like say a fralin or Gibson etc?
Yes. Also, Lollar has introduced a humbucker-size gold foil: https://www.lollarguitars.com/novel-foil
I haven’t tied it, but I want to!