Guitar & Bass Magazine
Guitar & Bass Magazine
VGI / Valhalla
Dirk Wacker – Premier Guitar / Valhalla
Hello, and welcome back to “Mod Garage.” Recently, I’ve received a lot of emails about tone caps for Stratocasters. I’ve discussed capacitors in general a few times before, and those earlier columns are a good place to start if you want to find out more about tone caps for guitars and how to determine the best value for you. Based on those, we’ll dig deeper into the subject, and concentrate on caps for Strats. I can give you advice about what to try based on my experience with different caps and Strats over the years, but there are no fixed rules. It’s your guitar and your sound, and there’s no law that says you can’t try whatever you want. Be brave and go wild, and maybe you’ll find something by accident that suits you exactly. One customer of mine uses only caps from a specific old German radio from the ‘50s. For him, it’s the perfect tone. If you have some old, obsolete electronic products in your cellar or attic, they’re a good source for some wild experiments. I received an email from a guy in Arkansas who opened up some old military stuff from the ‘50s and found tons of Sprague Bumblebee caps… some of them are now living their second life in his Les Paul and SG guitars, and providing superb tone.
In a nutshell, a capacitor is an electrical/ electronic device that stores energy in the electric field between a pair of conductors (called plates). The process of storing energy in the capacitor is known as charging, and involves electric charges of equal magnitude but opposite polarity building up on each plate. Capacitors are often used in electrical and electronic circuits as energy-storage devices. They can also be used to differentiate between high-frequency and low-frequency signals. This property makes them useful in electronic filters, and that’s exactly what we use them for in our guitars. Basically, our passive tone control can be used to dampen the high frequencies. When you close the tone pot, it rolls off the treble response, resulting in a more mellow tone. Adjusting this control affects the sound very noticeably, but it’s still recognizably the same guitar. As a basic rule, you could say the bigger the cap, the darker the tone. Depending on the cap’s value, or capacitance, the effect can go from slightly warmer (2200–6800pF) to a “woman tone” (0.01–0.047uF) up to completely dark and “clinically dead” (0.1uF and higher). Another thing to remember is that the tone cap is always part of the circuit and even influences the guitar’s tone when the tone pot is left fully open—that’s the reason the tone cap is such an important part of the sound.
Here are some caps you should try in your Strat:
These legendary caps were formerly produced by Sprague. Today they’re made by the American company SBE, but with the same old machines and the original tooling of the golden days. They are film types, available in different voltage ratings, sizes, shapes and values. The typical Orange Drop caps we know of are used in high-quality tube amps, especially the 630V types. These have the most “Fendery” tone when used in a Strat: slightly scooped mids and a tight, percussive bass response great for clean playing (and overdrive too). There are several different series available. The most common ones available from guitar parts suppliers are the 715P and the higher-graded 716P series. Both are polypropylene film types. The 225P and the PS series are polyester film types. These are the ones you should try in your Strat. They sound even more “Fendery” than the 715P and 716P series. As a film cap, the Orange Drop caps are non-polarized, so their orientation makes no difference… at least it should make no difference, but that’s a subject for a later column.
These axial-leaded polyester film caps, or “poly-film” caps, are easy to identify because of their bright yellow color, similar to the old Plessi caps you may know from the Music Man amps. The Mallory 150 caps are made by the Canadian company DuraCap. Because of the axial-leaded shape, they’re very easy to use in guitars. They sound very punchy with a good edge—a perfect Strat tone cap for blues and rock. With overdrive, they sound very mellow and musical. This cap works perfectly with single-coil pickups, but will work with humbuckers as well. If you want a modern, round tone, this is a cap you should try.
ERO Roederstein MKT1813
Made by Vishay, these are also axial-leaded polyester film caps, and they’re also yellow, but not as bright and shiny as the Mallory 150s. They have a very woody and transparent tone; in a Telecaster they can sometimes sound like an acoustic guitar. If your Strat has a very woody and resonant primary tone, this cap will bring it all to the surface when amplified.
NOS Styroflex caps
Often called “polystyrol” caps, you can find them easily on eBay today, even though they’re no longer in production. Polystyrene capacitors are best used for filters, timing circuits, feedback circuits and anywhere high stability and low leakage is important, but they also are great tone caps for guitars, amps and stompboxes. Polystyrene (PS, often called “Styroflex” or “styrol” in Europe) has long been the material of choice for critical analog circuits. Polystyrene caps are a perfect substitute for silver mica caps, but much smaller and easier to find in the typical values we use for guitars. If you want maximum transparency and no tone coloration at all, this is the type of cap you should try.
Next month we’ll talk about paper-in-oil caps, silver mica caps, tropical fish caps, paper waxed caps and the good ol’ NOS “high voltage” ceramic caps from the ‘50s and ‘60s. Until then… keep on modding!
Hello and welcome back to Mod Garage. Before I continue with the list of tone caps to try in your Strat (see part 1), I’d like to say a few words about the popular Luxe repro caps (luxeradio.com) that popped up on the market some years ago. These are faithful recreations to mimic the look of old vintage tone caps, and these guys are really doing a great job. I had some of them on the workbench and compared them carefully with the original caps. There is absolutely no difference in appearance—they really look like 50-year-old caps, and they even feel and smell like the old ones. But keep in mind that they are replicas, so they don’t sound just like the originals. If you want the perfect vintage look inside your electronics compartment, this is the way to go. Don’t get me wrong, the people at Luxe Radio & Musical Instrument Co. are doing everything to get their caps to sound close to the originals, so they are using the same type of construction. For example, the Luxe Bumblebee repro caps are vintage-masked, new old stock (NOS), Vitamin Q-style paper-in-oil caps from Russian military supply. These caps sound very good, but not exactly like an old “Bumblebee” or “Black Beauty.”
OK, so let’s continue with the list of tone caps you should try in your Strat.
Silver mica caps are made from a dielectric of mica with a silver dip coating, hence the name. Modern silver mica caps are easy to identify because they have a typical hump in the middle of the body. NOS silver mica caps usually have a flat, rectangular shape. They can be found inside high-quality amps and stompboxes. They can also be used as an excellent high-cut cap on a guitar’s volume pot. If you can find the correct value, they’re also excellent as a cap for the tone control. Higher values are often hard to find, big in size, and very expensive—but worth a try. They really sound excellent, without any coloration. They’ll improve a guitar’s tone dramatically, and they’ll improve top end and clarity due to their low-loss design—they’re the absolute best-sounding caps for tone circuits, tone stacks, and filters. A good substitute for silver mica caps are the Styroflex caps I mentioned last month. They’re much smaller in size, and therefore much easier to handle as a tone cap.
Paper-in-Oil (aka “PIO”)
These caps from Jensen, Sprague (Vitamin Q), Mundorf, and some others can usually be found in high-end hi-fi equipment like audio power supplies, decoupling stages, and speaker crossover filters, as well as high-quality guitar amps. They are very expensive, but many swear by them. Naturally, you can use them inside a guitar if you have enough space for such a tone cap. These capacitors use oil-soaked paper as dielectric material and are therefore well damped and very transparent, smooth, defined, punchy, and natural sounding— bandwidth is very high and distortion very low. The very early Sprague Bumblebee caps from the ’50s are PIOs, and they’re easy to identify because of the blob at one of the leads. Plenty of NOS PIO caps are available, and they’re excellent quality—some are even military graded—and they’re often cheaper than caps from Jensen and others.
Mullard/Philips C280 “Tropical Fish”
Mullard/Philips C280 “Tropical Fish” capacitors
The Mullard/Philips C280 capacitor became widely known as the “tropical fish” cap because of its colorful stripes, which are used to indicate its value. This cap is a polyester film type from the late ’60s, and you can find it in a lot of tube amplifiers and stompboxes from that era. It’s the magical wah-wah cap as well, so this is your ticket to converting your modern wah pedal into a vintage tone machine. The “tropical fish” term is often mixed up with the Bumblebee caps, but this is simply wrong. These have been out of production for decades but are still available as NOS caps. They sound excellent in a Strat, offering a very fat tone that doesn’t turn into mud with overdrive or distortion. Compared to the Orange Drop polyester film caps, these have more midrange and less high-end sizzle. If you have a thin-sounding Strat, they are worth a try.
Paper-Waxed (aka “PIW”)
An example of a paper-waxed (aka “PIW”) capacitor
This type of cap is one of the earliest constructions and it’s considered obsolete today. Paper capacitors are typically constructed of thin, flat strips of metal foil conductors that are divided by waxed paper. They’re sealed with wax to prevent the harmful effects of moisture and to prevent corrosion and leakage. You can find this type of cap in very early tube radios, TVs, and guitar amps as well. Fender used this type (which usually looks like a thick, rectangular blob of wax) as a tone cap in the earliest Broadcasters, Esquires, Telecasters, and Stratocasters. At that time, the 0.1uF value was standard, and it provided a very dark and muffled tone (I refer to it as “clinically dead”). The choice of this value was Leo Fender’s idea, to provide a “bassy” tone so the guitar player of a band could also play some bass lines if necessary. The most famous PIW tone cap in the guitar world is the tube-shaped Cornell-Dubilier “Grey Tiger” that Gibson used until 1956. Their construction aided and abetted a muffled tone with a dampened high-end and prominent bass and mid frequencies. Personally, I don’t like the sound of these caps, but they are original equipment on the earliest Fender guitars—so if you want to duplicate the early vintage circuits, there’s no way around them. The only application I would recommend for such a cap would be a very ice-picky, harsh-sounding Strat with tons of treble. These have been out of production for many years, but you can find them used (OS or “old stock”) or NOS on eBay.
NOS “High Voltage” Ceramic
A NOS “high voltage” ceramic capacitor
“High voltage” ceramic disc caps (aka “pancake caps”) from companies like those from Sprague, Centralab, Waldom, Mepco, and Erie were the standard tone caps on all Fender guitars during the ’60s and early ’70s. They look like brown chocolate drops, and many of them have voltage ratings up to 1kV and even higher. They are out of production now, but some companies still stock NOS supplies of these excellent-sounding caps. Another option is to get some consumer electronic devices from that era, like old TVs and radios, and cannibalize them. To achieve true ’60s vintage tone from your Strat, Tele, or P- or J-Bass, there’s no way around the original. They sound totally different from the modern ceramic caps. The difference really is stunning, and there are several theories as to why they sound so good. From a technical point of view, these caps are far from being perfect as capacitors, so lots of harmonics and upper tones pass through without being blocked—which is why most people say they sound excellent. They’re among my favorite caps as well, and often they are the difference between a very good-sounding guitar and a fantastic-sounding guitar. I’ve tried lots of modern ceramic caps, but nothing even comes close to the old ones. If you can get some of these, do!
All right, that’s it. Many more tone caps are available, but it wasn’t my intention to make an exhaustive list. I wanted to focus on the caps that work well in a Strat. NOS Bumblebee caps, for example, don’t sound very good in Fender guitars, so we’ll talk about these caps when we switch over to the Les Paul and 335 mods. Next month, we’ll close this chapter by discussing the orientation of caps. I’m sure there will be some surprises in store. Until then… keep on modding!
Hello, and welcome back to Mod Garage. To start this last installment about tone capacitors for Strats, I would like to tell you a story that happened to me some years ago. I swear it’s all true. Hopefully you will not send me to the stake after reading it—and no voodoo, either, please!
One of our customers, a professional guitarist from Switzerland, called and wanted to bring in a vintage guitar he had acquired a few days before, because “there was something wrong with the electronics.” When he arrived and opened up the case, there it was: a 1962 Stratocaster in all its glory! The guitar had obviously been played a lot, but other than a bunch of dings it was in very good condition. The previous owner had said it didn’t sound very good and sold it at a price our customer couldn’t pass up.
First Nirvana, Then Blah
I took it out of the case, tuned it, and noodled on a few chords and licks without plugging in. I was instantly stunned: It was one of the most acoustically vibrant guitars I’d ever played! The whole thing resonated—from the end of the body up to the headstock—you could even feel some notes when you touched the headstock. The overtones seemed to jump out of this guitar. I was in playing heaven.
However, after plugging the guitar into an amp, I was really disappointed. It didn’t sound bad—and the tone was noticeably Strat-y—but it was far away from being a fantastic-sounding guitar. None of the superb acoustic qualities were there. It just sounded average. As you may know, buying a vintage guitar does not guarantee good vintage tone. Over the years I’ve seen a lot of lemons from the Golden Age of guitar building, so I thought maybe this could be one of those guitars. I plugged it into my 1959 Bassman using a high-quality guitar cable, but the result was the same. I agreed with the customer that there had to be something wrong with the electronics. After unstringing the guitar, we opened it and found that most of the electronics were stock. There was one replaced tone pot, an Orange Drop tone capacitor, and a new ground wire running from the tremolo compartment to the case of the volume pot. That’s it, nothing too special. Pots can fail after such a long time, wires can break, and replacement tone caps are nothing uncommon. The pickups, switch, wiring, two of the three pots, and the output jack were absolutely stock.
The Ol’ Pickguard-Swap Test
My next step was to take out the pickguard, including the output jack, and put in an already-wired replacement pickguard that we use as a reference for testing. This pickguard is loaded with standard parts like CTS pots, a CRL 5-way switch, and a set of Fender 57/62 pickups. The goal was to create an average-quality pickguard for testing—nothing too fancy and nothing below average. After connecting everything and restringing the guitar, we plugged it in and it blew me away! Without any adjustment of the pickup heights, the sound was fantastic. Very transparent, punchy, and with all of the vintage Strat attributes we love. Our customer was totally freaking over how good the guitar sounded, and it took me some time to convince him to lay down the guitar again. You all know this special moment—playing and hearing your new guitar for the first time. It always brings a huge smile to your face. I guess you all know what happened then…after some adjustments, our test pickguard remained on the Strat as a loan while we promised to check and repair the original electronics.
To double-check everything, I temporarily installed the vintage pickguard on one of our test guitars, a standard Made-in-Mexico Fender Stratocaster. The result was the same. The tone was average and had no personality. I took some high-resolution pics for reference and then pulled all the parts out of the pickguard to test them. To make sure the pickups were OK, I soldered them, one by one, directly to the output jack. They all sounded fantastic. So it was clear that the pickups were fine and that the failure was somewhere in the wiring and/or the switches or pots. After unsoldering everything, I measured all the wires. They seemed OK. Same with the switch, the pots, the cap, and the output jack. After repeating all the checks again, I decided to reinstall everything and exchange one part after another to track down the faulty piece. After carefully reassembling all the guts, I was hit between the eyes: I put the pickguard on our test Strat and it sounded rich and beautiful— simply stunning. I tried to replicate the problem several times but failed. The guitar sounded great, and I had no clue why.
I compared the wiring and the arrangement of the parts with the pics I took several times, but it was all identical. I even marked all the wires to put them in the same place again.
Well, such things happen from time to time. The most important thing was that the failure was gone, which would guarantee me a satisfied customer. But the obscure phenomenon bothered me. So I let it cool down for a few days and then carefully compared everything with the pictures again. And there it was: I hadn’t noticed it before—because it shouldn’t make a difference—but I had installed the tone cap face up (so you can read what is printed on it, which makes things easier because you can clearly see the value). In the original configuration, the same cap had been installed face down, so it was 180 degrees reversed. I didn’t pay attention to this fact because Orange Drop caps are film/foil caps and don´t have an orientation like electrolytic caps. So the way they’re installed should not make a difference in tone. Since this was the only noticeable difference I could detect, I decided to test my own wits one more time. I reversed the cap the way it was originally installed, and I could hardly believe it: I plugged the guitar in and the average tone was back! It was like the life had been sucked out of it again.
An Orange Drop in the Forensics Lab
I wondered if the cap was faulty, so I tested it with a DMM and a scope but couldn´t find a problem. I handed the cap to a friend of mine who works at a test lab at the local university, and he did several intensive tests but couldn´t find anything unusual. It was in perfect working condition.
To find out how to avoid this same problem with your tone caps, stay tuned for next month´s column.
Until then, keep on modding!
Hello, and welcome back to “Mod Garage” for our last installment on tone caps for Stratocasters. I’ll also take a moment to finish the story about how our obscure tone cap turned out.
After receiving the Orange Drop cap back from the lab, I replaced it with an NOS Sprague “high-voltage” ceramic cap from the ‘60s to get the Strat as close as possible to stock ‘60s specs. Our customer was happy, and he’s still playing the guitar as his number one axe. I kept the Orange Drop cap for further testing and as a souvenir of a lesson learned.
Unfortunately, situations like this—when something is working, but nobody can tell you why—really bother me. We had traced a problem and found a workaround, but that’s an unpleasant situation. So I decided to dip deeper into the obscure world of film and foil caps.
Let’s resume: we have a 100-volt Orange Drop film and foil cap, formerly made by Sprague, today built by SBE with the original Sprague machines and toolings. These caps are produced by taking a long narrow strip of insulating material and placing a strip of metal foil on both sides of it. The two pieces of foil become the plates of the capacitor, and the insulator the dielectric. This long strip is then wound into a cylindrical shape, two metal leads are attached to the two foils, and the entire construction is potted and sealed in some type of material designed to keep moisture out of the capacitor and to keep the capacitor mechanically stable. Since the capacitor is wound into a cylindrical shape, one of the foil sides is on the outside (referred to as the “outside foil” end), and the other on the inside (“inside foil” end).
Standard film and foil caps don’t have a certain orientation like electrolytic caps, so, in theory, the way they are installed inside a guitar should not make any difference in tone. So why is this important when it doesn’t make a difference, tonally? Well, the outer-foil side can be used as a shield against electric field coupling into the capacitor—very important for tube amps. In order to take advantage of the shielding properties of the outside foil, the cap must be connected in the circuit in a particular orientation, which is the low impedance side of the amp circuit.
In a passive guitar circuit, there is no low-impedance side because we use the tone cap as a bypass cap to ground, so the outside foil should be connected to the grounded side in this case. The outside foil will act as a shield against electric field coupling into the capacitor, so you want it to have the lowest impedance return path to ground. With this rule in mind and all the caps connected this way, a tube amp will be much less susceptible to interference from fluorescent lighting and hum, oscillations or frequency-response peaks due to unwanted feedback from nearby signals within the amp.
So, I started to reverse the tone caps inside different guitars, and to my surprise, I discovered the following:
So why is he talking about all this, you may ask? I simply want to encourage you to keep your ears open! If you have a good-sounding guitar that has a bad amplified tone, try reversing the tone cap(s) before you blame the pickups and spend a lot of hard-earned bucks on a new set.
Unfortunately, identifying the outside foil end of such caps isn’t always easy. Some caps have a mark to indicate this side, but because the procedure takes time, most manufacturers don’t mark their caps. To bust another internet myth, I spoke with a SBE engineer who had also worked for Sprague in the past. He said that neither Sprague nor SBE marked the outside foil on Orange Drop caps! (He did say that there are plans to offer that option in the future for custom production runs).
According to the same engineer, the banded mark you can find on older Sprague Orange Drop caps was related to the production process Sprague used at this time, whatever that means. I crosschecked this with several old Orange Drops and can confirm the banded mark is not indicating the outside foil side.
So what if the cap is not marked? To find out where the outside foil side is connected, you will need some know-how and a good scope. I don’t have the space to detail this testing procedure, but if you are interested, please send me an email. That said, since there are only two terminals, you have a 50-50 chance to get it right from the start.
The moral of this story? If you love to mod your guitars and your guitar is loaded with Orange Drops, Mallorys, Roedersteins, WIMAs or similar caps, listen to the guitar’s amplified tone, reverse the tone cap(s) and listen again. Chances are that you will hear a noticeable difference in tone, as long as you aren’t using single-layer or high-voltage film and foil caps. Who knows—maybe you will discover one of your old guitars again, unplayed for years because of a less-than-great amplified tone!
Next month we’ll return to Stratocaster mods, and I will detail a very cool mod called the “vintage coiled guitar cable simulator.” Until then, keep on modding!