Drawing courtesy of SINGLECOIL
In general, it’s possible to use the Varitone/Tone Expressor system in any electric guitar as long as you have enough space to squeeze all the stuff into it. You can mimic a lot of different pickups with this system, but because it’s designed for guitars with humbuckers, that’s how it works best. It’s also possible to use it the other way around and thicken up single-coil pickups instead of slenderizing humbucker tones, and in a future column I’ll talk about what I like to call the “reverse Varitone” system.
For a good and simple overview about all the details from last month, I decided to use a technical drawing to show the isolated Varitone system, so it’s easy for you to identify the individual parts:
Diagram courtesy of SINGLECOIL
This is the basic structure of the Gibson Varitone system with the original values Gibson used. The inductor is a 1.5 H choke. The Epiphone Tone Expressor system is identical but uses a 15 H choke as an inductor. There is a second version of the Tone Expressor system found on the Al Caiola model using the same structure but with different values for the parts. I think this was because different pickups were used, so here are the values for the version of the system in the Al Caiola guitar:
• 15 H choke as an inductor instead of 1.5 H
• Replace the single 100k resistor with a 33k resistor
• .0033 µF cap is used instead of the .001
• .01 µF cap is used instead of the .0033
• .022 µF cap is used instead of the .01
• .047 µF cap is used instead of the .03
• .1 cap µF is used instead of the .22
For best results, use the original Gibson Varitone values along with PAF-style humbuckers—the second version will work best with mini-humbuckers or similar pickups. Depending on the pickups you use, you can experiment and make your own custom version out of it.
“You can mimic a lot of different pickups with this system, but because it’s designed for guitars with humbuckers, that’s how it works best.”
The differences are:
• Using a 15 H instead of the 1.5 H inductor will shift the notches of the filters created by the Tone Expressor system down approximately a fifth for a fuller and fatter tone. Because it is possible to combine several caps with this wiring, choosing a 15 H inductor was also a clever move to keep the tone clearer and more present. You can experiment with this, too. A choke with something between 7 and 10 H will be in the middle of both versions.
• Using a 33k instead of the 100k coupling resistor fits pickups with a lower output like the mini-humbucker perfectly, while the 100k is great for pickups with more output like a PAF.
• The different cap values also correspond to the combination of different pickups and chokes, e.g., for a twangy, Telecaster-type tone, you need a 0.22 µF cap along with a PAF humbucker, while a 0.1 µF cap will do the same along with a mini-humbucker.
So, here we go with the Al Caiola wiring, starting with how it looks in the original guitars from the ’60s. You can clearly see the big, silver-cased choke on top of the electronics as well as the caps, resistors, and the individual switches.
Photo courtesy of Bonfires Vintage
And here is the drawing of the Tone Expressor system I made for you:
Drawing courtesy of SINGLECOIL
All switches are DPDT switches, the tone and volume pots are both 500k audio, and the tone cap is 0.022 µF. A is the coupling resistor (33k or 100k), B is the five 10M ohm pulldown-resistors (one on each switch), which prevent popping noises when engaging a switch, and C is an additional 33k decoupling resistor on each switch that is necessary to decouple the switches from each other when you want to combine their settings. You don’t need that on the Varitone because you can’t combine several caps with the rotary switch.
Besides experimenting with the parameters of the choke, the caps, and the coupling resistor, you can enhance your tonal palette quick and easy by using a pickup selector switch that can engage both pickups together.
In closing, here is a scaled-down version of this wiring, in case you don’t want to use a choke or can’t find one.
Drawing courtesy of SINGLECOIL
As you can see, the coupling resistor (A) and the decoupling resistors (C) are removed. That’s because in the system with the choke (second order filter system), these are necessary, but without a choke, they’re not.
That’s it. Since we are still in the year of the Strat, next month we will have a look into the Fender Cory Wong Stratocaster, so stay tuned!
Until then, keep on modding!
This 1968 Epiphone Al Caiola Standard came stocked with P-90s and a 5-switch Tone Expressor system.
Photo courtesy of Guitar Point (guitarpoint.de)
The Epiphone Al Caiola model was built in the Gibson Kalamazoo factory and was similar to an Epiphone Sheraton, with a longer 25 1/2" scale. It was built from late 1963 until 1969 and was available with different pickups like Gibson mini-humbuckers and P-90s. The guitar would be renamed the Al Caiola Custom to make way for the Al Caiola Standard that was introduced in 1966, but both models had the Tone Expressor system.
The guitar has a Telecaster-like wiring configuration: two pickups, master volume and master tone, 2-way pickup-selector switch. Since the circuit only has a 2-way switch instead of a 3-way switch, you can’t play both the neck and bridge pickup at the same time. (Maybe Al Caiola didn’t like a middle-position sound; who knows?) There are also five additional mini-slider switches labeled 1—5 which make up the Tone Expressor system.
“With the individual slider switches of the Tone Expressor system, you can combine all five switching positions in any way you like, so you have countless possible combinations.”
Having a look under the hood reveals the Gibson Varitone system used on the ES models. My first thought was this was new wine in old bottles, but after having a deeper look, there are differences between the standard Gibson Varitone and the Tone Expressor system. The Gibson Varitone uses a 1.5 H inductor, while the Tone Expressor system has a 15 H inductor on board. The Varitone is a rotary switch, so you can only dial in one of the switching positions, no combinations. With the individual slider switches of the Tone Expressor system, you can combine all five switching positions in any way you like, so you have countless possible combinations. Electronically, the Tone Expressor is a switchable band-rejection filter; mids are attenuated and the result is a crisp, more twangy tone.
In this first of two parts about this very special circuit, I want to describe the switching positions of the Tone Expressor system. First, here are the individual parts:
• 500k audio master volume and master tone pot with a 0.02 μF tone cap. This configuration will work with mini-humbuckers as well as P-90 pickups.
• 2-way pickup-selector slider switch. Having the possibility to engage both pickups together (no matter if in parallel or in series) would enhance this wiring noticeably.
• 15 H inductor (choke). The inductor in this circuit creates a series of notch filters together with the caps of the individual switches, so the circuit doesn’t remove all signal above a certain frequency, but only a certain amount above and below that frequency. There is a lot of debate about using an inductor or not, and if so, what type.
Personally, I think adding an inductor is not the best choice. The design may have worked at the time, but today, most of us are looking for different sounds. While the Varitone has its fans, it was never very popular because it can suck tone, and a lot of people say that it doesn’t have a major effect anyway.
If you want to use an inductor and find a matching one, these have center-tapped primaries and secondaries. Use the entire primary or the entire secondary, and ignore center taps for the Varitone wiring. I had the chance to measure several original inductors (labeled TF-90-1C), and they all showed something between 12 H and 17 H; keeping their tolerances in mind, you can use any inductor in this ballpark.
• 10 M resistors. There is a 10 M resistor connected to the circuit in series to each of the five caps. These “pull-down” resistors prevent loud popping noises when using one of the switches—standard when switching capacitance like on the Varitone system.
• 100k resistor. Together with the caps on the switches, the single 100k series resistor creates a frequency selective voltage divider, which is essential to create a proper frequency notch. The value is well-chosen so there is no need to replace it.
On the Varitone rotary switch, position No. 1 is the bypass mode. The Al Caiola, with its slider switches, naturally doesn’t need an extra switch for this. When no switch is engaged, the Tone Expressor system is in bypass mode. In general, we can say that the bigger the cap, the thinner the tone, and vice versa. Or in other words: The bigger the cap, the more the humbucker tone is tidied up towards a more twangy and single-coil-like tone.
An up-close look at the controls for the Tone Expressor system.
Photo courtesy of Guitar Point (guitarpoint.de)
Here is what each switching position does:
• Switch No. 1 with 1000 pF cap corresponds to position two of the Varitone rotary switch and has a very subtle effect. It’s an unmistakably PAF-style humbucker tone, but with the bass frequencies tidied up a little. This setting can help cut through a mix and will prevent a boomy, woolly tone when playing full-tilt.
• Switch No. 2 with 3000 pF cap corresponds to position three of the Varitone rotary switch and is my favorite setting. Still a PAF-style humbucker tone, but tighter and with more transparency. This tone never gets too boomy and rides on the edge of the P-90 territory.
• Switch No. 3 with 0.01 μF cap corresponds to position four of the Varitone rotary switch. This reminds me of a typical P-90 tone with a tight bass and clarity in the high frequencies—very cool for some break-up blues playing.
• Switch No. 4 with 0.03 μF cap corresponds to position five of the Varitone rotary switch and is a very twangy and single-coil like setting that sounds like a Stratocaster—very useful and versatile.
• Switch No. 5 with 0.22 μF cap corresponds to position six of the Varitone rotary switch and is the most twangy setting. It reminds me a lot of a good Telecaster, especially with the bridge pickup.
Next month, we will look into different ways to set up and mod this circuit, so stay tuned!
Until then ... keep on modding!
In general, Leo Fender’s credo was that “the design of each element should be thought out in order to be easy to make and easy to repair.” His approach was to build high-quality instruments while maintaining low manufacturing costs with mass production. When thinking about the design of the Stratocaster, there are at least two elements where one can have some doubts about the easy-to-repair approach, at least from today’s perspective: pickguards you can’t take off without removing the strings and truss rods you can’t access without removing the pickguard.
Within the historical context of Leo Fender’s time, I think he would say that he did everything right. Right from the start, the Fender company cared a lot about setting up their guitars before they were shipped out. The setup was meant to be set-it-and-forget-it, so truss rod access was not very important—accessing it from the neck heel was the design following function.
I’m not sure if this was really easier to build this way compared to accessing it from the headstock, but it was the method that offered better headstock stability and longevity. Nine out of 10 Stratocaster headstock repairs I see in the shop are guitars with truss-rod access from the headstock. Because of its design, this is a weak spot in the wood, so drilling a hole to access the truss rod will weaken it more. In old Fender papers I found an interesting bulletin that the neck was never meant to be repaired or refretted. Instead, a customer was simply meant to change the complete bolt-on neck.
Back in the ’50s, things like replacement pickups, mods, push-pull pots, multi-stage pickup switches, and the like were not yet invented, so there was no need to design the Stratocaster pickguard for easy access. It would only have to be removed for a serious repair, which shouldn’t have happened very often.
Times have changed noticeably, and today it is usual to perform a setup regularly to compensate for changing weather conditions, different string gauges, and so on. And trying new pickups, tone caps, mods, etc. is a kind of popular sport among most guitarists—set-it-and-forget-it was forgotten long ago!
“Back in the ’50s, things like replacement pickups, mods, push-pull pots, multi-stage pickup switches, and the like were not yet invented, so there was no need to design the Stratocaster pickguard for easy access.”
The design of the Stratocaster hasn’t changed much since the mid ’50s. Of course, standard procedure is now to have truss-rod access from the headstock, so at least the setup thing is finally solved. But Stratocasters with access to the pickguard from behind is something that would make a lot of things much simpler. Let’s see what can be done to make things easier and, of course, faster when you do have to remove your guitar’s neck or loosen the strings to get to the pickguard.
The gold standard way of servicing a Stratocaster is to remove the old strings so you have full access to the pickguard. This is especially perfect when you want to do some work under the hood of the pickguard like changing a pot, pickup, or any other electronics work. You can test everything before you put on the new strings and there is no additional work to consider. For setups this is a great starting point—you can roughly pre-adjust the neck to your preferences, but for the final setup, there is no way around putting on the new set of strings. Here are two of my favorite hacks in the shop to save some time and nerves.
The IKEA Hack
You all know these plastic kitchen sealing clips for resealing opened bags and packages. I like the IKEA model because they’re super sturdy, well-made, and will last a very long time. Take one of these clips—we will need the large version—open it, and cut six small grooves in it using a round needle file or any other similar tool for this. Try to come close to the string spacing behind the nut with your grooves. I usually take a black sharpie to mark the spacing on the plastic clip before using the file.
Photo courtesy of SINGLECOIL
After you’re finished, loosen the strings but don’t take them out of the tuner posts. Slide the opened clip under the strings behind the nut, put each string in one of the grooves, and close the clip. Now, you can pull the strings out of their posts and put them aside to have full access to the pickguard and the neck-heel truss rod. Because the modified clip will hold the strings in place, they will not tangle up into a bird’s nest of strings. For vintage-Kluson-style tuners or locking tuners, it can be very easy to pull the strings out of the posts and back in. For other types, you’ll need a little bit more patience to get the strings back in place, but it’s worth the effort.
The Old-Style Capo Hack
My first capo that I got when I was around 10 years old or so is still alive and employed in my shop. It’s a Dunlop 11C toggle-action capo that is still in production, and I bet a lot of you started with this capo, too. I use the curved version that my parents bought by accident for my classical guitar because they didn’t know about flat and curved fretboards. This one works great on all electric guitars.
Photo courtesy of SINGLECOIL
Loosen all the strings slightly so they will not slip out of their posts. Put the capo on the first fret and close it. The strings can no longer slip out of the nut, the string trees, and the posts of the tuners.
Photo courtesy of SINGLECOIL
Now, when you remove the neck, the capo will hold the strings in place. Putting the neck back on will be very easy: Fasten the screws, take off the capo, and tune the strings to pitch.
You see, there are at least two alternative ways to avoid changing the strings, especially if they are as good as new with only a few playing hours upon them. Often, little gizmos make a big difference.
Next month we will dive down into Epiphone history and see what they electronically cooked up in the mid ’60s, so stay tuned.
Until then ... keep modding!