
Dave Hunter kicks off a two-part primer on tubes with some general history on our glowing glass friends and an in-depth look at preamp tubes.
Welcome to a two-part feature in Premier Guitar that will give the uninitiated all the basics needed to help them launch their quest for tubehead status. We'll also provide plenty of under-the-hood details to further bolster the knowledge of players who are already in the know about these glorious audio devices. I'll discuss preamp tubes this issue and output (power) tubes next issue, but before diving in, let's take a brief look at how tubes perform their sonic magic in the first place.
Once upon a time, vacuum tubes were used all over the place. They glowed their little hearts out in our television sets, car and home radios, hi-fi systems, and guitar amplifiers, and were crucial components in myriad military applications, from radar technology to missile guidance systems and more. Bit by bit they have been replaced in all of these functions by other forms of more compact and more stable technology… except in guitar amps, where they maintain their preeminence over all kinds of far more advanced electronics. Is this just nostalgia, or mere perversity on the part of guitarists? Not in the least: when used to amplify electric guitars, tubes still simply sound better than anything else out there. Sure, there are some respectable sounding solid-state amps, and digital modeling amps have also made inroads into the market, but ninety-nine out of a hundred serious pros (if not more) continue to use tube amps for both recording and touring, and these little glowing bottles still define the cornerstone tones of rock, blues, and country guitar.
To get quickly to the heart of tube magic, stop thinking of them as amplification devices and start thinking of them as tone-generating devices. A tube-based amp makes your guitar louder, sure, but tubes amplify your electric guitar so beautifully mainly because of the way they distort. To put it as briefly and concisely as possible: push a simple transistor circuit hard, and it clips (distorts) in a sudden, harsh, "square wave" way; push a tube into clipping and it distorts more gradually and more smoothly—it "rounds off" into distortion—and slathers on a gorgeous gravy of harmonics along the way. There are a lot of other factors involved, of course, but that gets us to the nut of it.
This is why any decent sounding solid-state amp requires a lot of extra circuitry to do what a very simple tube amp circuit can do naturally. And be aware, too, that when I'm talking about distortion, I'm also referring to sonic elements that influence your so-called "clean tone." Most tube amps, even when set to clean levels (unless you've got the volume of a powerful amp set extremely low) are still distorting a little, and that distortion creates layers of harmonic depth that sweetens and fattens up that thing that we call our tone, even when we're playing "clean."
All amplification tubes carry at least four elements within their vacuum-sealed glass bottles: a cathode, a grid, a plate (also called "anode"), and a filament (or "heater"). The most basic tubes are called "triodes," named for the first three of these elements (a filament is always present, so it's ignored in the naming process). Pentode tubes, which account for most output tubes and a few preamp tubes, carry two further grids—a screen grid and a suppressor grid—that help to overcome capacitance between the control grid and the plate.
In simple terms, a tube's job is to make a small voltage (guitar signal) into a bigger one. How do they do this? Pluck a string on your guitar and the pickup sends a small voltage to the input of your amplifier, where it is passed along to the grid of the first preamp tube (think of it as the "input" of this tube). The increase in voltage at the grid causes electrons to boil off of the cathode and onto the plate at a correspondingly increased rate and, voila, the sound gets bigger. This slightly bigger signal from the preamp is passed along to the output stage, where the output tubes make it even bigger, to carry it on to the speaker via the output transformer.
(Note: some people refer to the latter as "power tubes", but I prefer "output" tubes because that better defines their function, whereas "power" might be confused with the power stage within the amp, AC/DC voltage conversion, and the work done by rectifier tubes, which is a different function altogether.)
Preamp tubes and output tubes do essentially the same thing, just with varying degrees of bigness, if you will. Tubes are literally the amplifiers at the heart of your amplifier: they do the real amplification work, and everything else inside the box is there to help them run efficiently and to help pass along the signal. Of course, in addition to early amplification duties, preamp tubes are also used for other functions within the amp: to drive reverb or tremolo stages, for example, or to split the signal and reverse the phases of the two legs that are fed to the output tubes.
Preamp tubes are easily identified, in most cases, as the smaller bottles in your amp, and are usually positioned to correspond to your amp's inputs and early gain and tone stages. Sometimes they are covered with metal shields, which are easily removed. Since the mid-fifites, preamp tubes have mostly been of the smaller ninepin variety, although some older amps will still have bigger eight-pin (or "octal") tubes that fit the same sockets used by many types of output tubes. The most common type by far is the 12AX7 (also known by the designation ECC83 in Europe, or the high-grade US alternative 7025).
Some other types you will occasionally see look much the same, other than the numbers printed on them. These are: the 12AT7, often used in reverb-driver and phase-inverter stages; the 12AY7, original equipment in the first gain stages of many legendary Fender tweed amps of the mid and late fifties; and the 5751, a lower-gain replacement for the 12AX7. All of these are what we call "dual triode" types, because they contain two independent tubes within the same bottle. They are mostly differentiated by their gain factor— the degree with which they increase the signal they are given. The 12AX7 has the most gain of the bunch, and the 12AY7 and 5751 are direct substitutes with less gain, which in many cases means they'll distort the early stages of the amp less. The 12AT7 also has less gain than the "AX," but requires a slightly different bias voltage for optimal operation (it can be directly substituted in a pinch).
The only pentode preamp tube seen with any regularity in amps today is the EF86 (or 6267), which appeared in early Vox amps and has more recently been used in models from Matchless, Dr Z, 65amps, and a few others. Another less frequently seen, but much admired, pentode preamp tube is the 5879, notably used in Gibson's GA-40 Les Paul amp of the late fifties. Both of these pentodes fit the same 9-pin bottle as the dual triodes but require very different circuitry, and are known for their thick, robust sound. Both have higher gain factors than even a 12AX7, but aren't prone to distorting the way that dual-triodes can, and instead pass their fattened-up signal on to the next stage. They also have a reputation for handling effects pedals very well. Drive a 12AX7 hard, however, and it will induce quite a bit of sizzling, slightly fizzy-voiced distortion of its own. This can be a great thing if you're looking for a super-fried overdrive tone that's cooking at all stages, but not at all desired if you want more headroom and clarity, or the fatter distortion that's generated in the output stage of the amp when a cleaner preamp signal is driven into clipping at the output tubes (more of which in the next installment).
Some modern high-gain amps are designed specifically to create extreme yet controllable preamp tube distortion by cascading multiple gain stages, one into the other, with gain and master volume controls between them to control the drive levels at each stage. Used in this way, preamp tubes can produce a scorching, harmonically saturated lead tone that sustains all day—what we usually hear as a classic shred or contemporary rock tone—in an amp that really relies on its output tubes just to amplify this sound, rather than to add further distortion to it. When driven into distortion in a simpler, more basic amp with fewer gain stages (a category that might nevertheless include some very high-end, "boutique" tube amps), preamp tube distortion becomes just a part of the amp's overall distortion character, blended with clipping at the phase inverter and output stages, and often at the speaker too.
Counter-intuitive though it might sound, armed with the above knowledge regarding preamp tube distortion, many players have learned to create a bigger tone by using lower gain preamp tubes. To lower the gain of a preamp stage a little, you can swap a 5751 into any socket that carries a 12AX7. To lower it even more but retain the same performance characteristics (other than gain) you can use a 12AY7. Many players think the last thing they want to do is lower the gain of a preamp stage, but in doing so you can often prevent your signal from dirtying up in the preamp, and thereby pass a beefy, full-frequencied signal along to the output stage when the amp is cranked. This generates more output tube distortion, which results in a fatter, fuller tone in many simpler tube amps. This tip doesn't usually apply to high-gain type tube amps, whose whole raison d'etre is to generate preamp distortion. This 5751 swap is a trick that was used by Stevie Ray Vaughan, for one, to help generate his signature tone, and it has also been employed by plenty of other great blues players. If you're trying distortion and more output-tube distortion, you can also try using a 5751 in the phase inverter position, which is usually the last preamp tube before the output tubes.
Note: the term NOS, which stands for "new old stock", is applied to tubes manufactured many years ago but never put into use.
Even tubes of exactly the same type can sound quite different, depending upon their manufacturer and small changes in their design and production. The fact that tubes distort so organically also means that no two tubes distort or even amplify exactly alike. For one thing, while tubes are manufactured under fairly rigorous conditions, they are still imperfect devices. Every little fluctuation in assembly or materials results in a slightly different sound and performance from each tube that comes along.
That's why good tube distributors need to routinely test tubes they sell: put even two high-quality NOS preamp tubes from highly respected American or British manufacturers on a tube tester—say, a pair each of Mullard or RCA 12AX7 preamp tubes that came out of the factory on the same day in 1963—and they will most likely have slightly different readings for gain and other factors. Put enough of them up on a tube tester and some will even fail to meet required minimum standards. That's the way it is. Aside from giving different readings, these tubes will each sound just a little different, and other makes, both NOS and current, will sound different again.
What does this mean for the guitarist? For one thing, it behooves you to get your hands on as many different makes and types of tubes as you can reasonably afford. Try swapping a few around to see which ones help you to best achieve the tone you are seeking. The first preamp tube position usually affects the tone of that part of the amp the most (read your amp's tube chart or owner's manual to make sure you know how to change tubes safely, and are changing the right tube, and please don't touch any hot tubes! Let them cool down first). Try three different makes of 12AX7 or their equivalent in that position, and I'm willing to bet you'll notice a slightly different voice from each. Search the internet and read up on what other players consider to be the best current- manufacture tubes coming out today (there's too much detail on that subject to go into here). Also, see if you can find any affordable NOS tubes, or perhaps you can pull some used but functioning examples from old junker radio or hi-fi systems that you find at garage sales and swap meets. Experiment a little, and see which ones work for you. Preamp tube tasting can become addictive, and it's also a great way to fine-tune your tone.
[Updated 9/1/21]
A live editor and browser for customizing Tone Models and presets.
IK Multimedia is pleased to release the TONEX Editor, a free update for TONEX Pedal and TONEX ONE users, available today through the IK Product Manager. This standalone application organizes the hardware library and enables real-time edits to Tone Models and presets with a connected TONEX pedal.
You can access your complete TONEX library, including Tone Models, presets and ToneNET, quickly load favorites to audition, and save to a designated hardware slot on IK hardware pedals. This easy-to-use application simplifies workflow, providing a streamlined experience for preparing TONEX pedals for the stage.
Fine-tune and organize your pedal presets in real time for playing live. Fully compatible with all your previous TONEX library settings and presets. Complete control over all pedal preset parameters, including Global setups. Access all Tone Models/IRs in the hardware memory, computer library, and ToneNET Export/Import entire libraries at once to back up and prepare for gigs Redesigned GUI with adaptive resize saves time and screen space Instantly audition any computer Tone Model or preset through the pedal.
Studio to Stage
Edit any onboard Tone Model or preset while hearing changes instantly through the pedal. Save new settings directly to the pedal, including global setup and performance modes (TONEX ONE), making it easy to fine-tune and customize your sound. The updated editor features a new floating window design for better screen organization and seamless browsing of Tone Models, amps, cabs, custom IRs and VIR. You can directly access Tone Models and IRs stored in the hardware memory and computer library, streamlining workflow.
A straightforward drop-down menu provides quick access to hardware-stored Tone Models conveniently sorted by type and character. Additionally, the editor offers complete control over all key parameters, including FX, Tone Model Amps, Tone Model Cabs/IR/VIR, and tempo and global setup options, delivering comprehensive, real-time control over all settings.
A Seamless Ecosystem of Tones
TONEX Editor automatically syncs with the entire TONEX user library within the Librarian tab. It provides quick access to all Tone Models, presets and ToneNET, with advanced filtering and folder organization for easy navigation. At the same time, a dedicated auto-load button lets you preview any Tone Model or preset in a designated hardware slot before committing changes.This streamlined workflow ensures quick edits, precise adjustments and the ultimate flexibility in sculpting your tone.
Get Started Today
TONEX Editor is included with TONEX 1.9.0, which was released today. Download or update the TONEX Mac/PC software from the IK Product Manager to install it. Then, launch TONEX Editor from your applications folder or Explorer.
For more information and videos about TONEX Editor, TONEX Pedal, TONEX ONE, and TONEX Cab, visit:
www.ikmultimedia.com/tonexeditor
The luthier’s stash.
There is more to a guitar than just the details.
A guitar is not simply a collection of wood, wire, and metal—it is an act of faith. Faith that a slab of lumber can be coaxed to sing, and that magnets and copper wire can capture something as expansive as human emotion. While it’s comforting to think that tone can be calculated like a tax return, the truth is far messier. A guitar is a living argument between its components—an uneasy alliance of materials and craftsmanship. When it works, it’s glorious.
The Uncooperative Nature of Wood
For me it all starts with the wood. Not just the species, but the piece. Despite what spec sheets and tonewood debates would have you believe, no two boards are the same. One piece of ash might have a bright, airy ring, while another from the same tree might sound like it spent a hard winter in a muddy ditch.
Builders know this, which is why you’ll occasionally catch one tapping on a rough blank, head cocked like a bird listening. They’re not crazy. They’re hunting for a lively, responsive quality that makes the wood feel awake in your hands. But wood is less than half the battle. So many guitarists make the mistake of buying the lumber instead of the luthier.
Pickups: Magnetic Hopes and Dreams
The engine of the guitar, pickups are the part that allegedly defines the electric guitar’s voice. Sure, swapping pickups will alter the tonality, to use a color metaphor, but they can only translate what’s already there, and there’s little percentage in trying to wake the dead. Yet, pickups do matter. A PAF-style might offer more harmonic complexity, or an overwound single-coil may bring some extra snarl, but here’s the thing: Two pickups made to the same specs can still sound different. The wire tension, the winding pattern, or even the temperature on the assembly line that day all add tiny variables that the spec sheet doesn’t mention. Don’t even get me started about the unrepeatability of “hand-scatter winding,” unless you’re a compulsive gambler.
“One piece of ash might have a bright, airy ring, while another from the same tree might sound like it spent a hard winter in a muddy ditch.”
Wires, Caps, and Wishful Thinking
Inside the control cavity, the pots and capacitors await, quietly shaping your tone whether you notice them or not. A potentiometer swap can make your volume taper feel like an on/off switch or smooth as an aged Tennessee whiskey. A capacitor change can make or break the tone control’s usefulness. It’s subtle, but noticeable. The kind of detail that sends people down the rabbit hole of swapping $3 capacitors for $50 “vintage-spec” caps, just to see if they can “feel” the mojo of the 1950s.
Hardware: The Unsung Saboteur
Bridges, nuts, tuners, and tailpieces are occasionally credited for their sonic contributions, but they’re quietly running the show. A steel block reflects and resonates differently than a die-cast zinc or aluminum bridge. Sloppy threads on bridge studs can weigh in, just as plate-style bridges can couple firmly to the body. Tuning machines can influence not just tuning stability, but their weight can alter the way the headstock itself vibrates.
It’s All Connected
Then there’s the neck joint—the place where sustain goes to die. A tight neck pocket allows the energy to transfer efficiently. A sloppy fit? Some credit it for creating the infamous cluck and twang of Fender guitars, so pick your poison. One of the most important specs is scale length. A longer scale not only creates more string tension, it also requires the frets to be further apart. This changes the feel and the sound. A shorter scale seems to diminish bright overtones, accentuating the lows and mids. Scale length has a definite effect on where the neck joins the body and the position of the bridge, where compromises must be made in a guitar’s overall design. There are so many choices, and just as many opportunities to miss the mark. It’s like driving without a map unless you’ve been there before.
Alchemy, Not Arithmetic
At the end of the day, a guitar’s greatness doesn’t come from its spec sheet. It’s not about the wood species or the coil-wire gauge. It’s about how it all conspires to either soar or sink. Two guitars, built to identical specs, can feel like long-lost soulmates or total strangers. All of these factors are why mix-and-match mods are a long game that can eventually pay off. But that’s the mystery of it. You can’t build magic from a parts list. You can’t buy mojo by the pound. A guitar is more than the sum of its parts—it’s a sometimes unpredictable collaboration of materials, choices, and human touch. And sometimes, whether in the hands of an experienced builder or a dedicated tinkerer, it just works.
MT 15 and Archon 50 Classic amplifiers offer fresh tones in release alongside a doubled-in-size Archon cabinet
PRS Guitars today released the updated MT 15 and the new Archon Classic amplifiers, along with a larger Archon speaker cabinet. The 15-watt, two-channel Mark Tremonti signature amp MT 15 now features a lead channel overdrive control. An addition to the Archon series, not a replacement, the 50-watt Classic offers a fresh voice by producing retro rock “classic” tones reminiscent of sound permeating the radio four and five decades ago. Now twice the size of the first Archon cabinet, the Archon 4x12 boasts four Celestion V-Type speakers.
MT 15 Amplifier Head
Balancing aggression and articulation, this 15-watt amp supplies both heavy rhythms and clear lead tones. The MT 15 revision builds off the design of the MT 100, bringing the voice of the 100’s overdrive channel into its smaller-format sibling. Updating the model, the lead channel also features a push/pull overdrive control that removes two gain stages to produce vintage, crunchier “mid gain” tones. The clean channel still features a push/pull boost control that adds a touch of overdrive crunch. A half-power switch takes the MT to 7 watts.
“Seven years ago, we released my signature MT 15 amplifier, a compact powerhouse that quickly became a go-to for players seeking both pristine cleans and crushing high-gain tones. In 2023, we took things even further with the MT 100, delivering a full-scale amplifier that carried my signature sound to the next level. That inspired us to find a way to fit the 100's third channel into the 15's lunchbox size,” said Mark Tremonti.
“Today, I’m beyond excited to introduce the next evolution of the MT15, now featuring a push/pull overdrive control on the Lead channel and a half-power switch, giving players even more tonal flexibility to shape their sound with a compact amp. Can’t wait for you all to plug in and experience it!”
Archon Classic Amplifier Head
With a refined gain structure from the original Archon, the Archon Classic’s lead channel offers a wider range of tones colored with gain, especially in the midrange. The clean channel goes from pristine all the way to the edge of breakup. This additional Archon version was developed to be a go-to tool for playing classic rock or pushing the envelope into modern territory. The Archon Classic still features the original’s bright switch, presence and depth controls. PRS continues to stock the Archon in retailers worldwide.
“The Archon Classic is not a re-issue of the original Archon, but a newly voiced circuit with the lead channel excelling in '70s and '80s rock tones and a hotter clean channel able to go into breakup. This is the answer for those wanting an Archon with a hotrod vintage lead channel gain structure without changing preamp tube types, and a juiced- up clean channel without having to use a boost pedal, all wrapped up in a retro-inspired cabinet design,” said PRS Amp Designer Doug Sewell.
Archon 4x12 Cabinet
As in the Archon 1x12 and 2x12, the mega-sized PRS Archon 4x12 speaker cabinet features Celestion V-Type speakers and a closed-back design, delivering power, punch, and tight low end. Also like its smaller brethren, the 4x12 is wrapped in durable black vinyl and adorned with a British-style black knitted-weave grill cloth. The Archon 4x12 is only the second four-speaker cabinet in the PRS lineup, next to the HDRX 4x12.
PRS Guitars continues its schedule of launching new products each month in 2025. Stay tuned to see new gear and 40 th Anniversary limited-edition guitars throughout the year. For all of the latest news, click www.prsguitars.com/40 and follow @prsguitars on Instagram, Tik Tok, Facebook, X, and YouTube.
The Austin-based guitarist sticks with a tried-and-true combo of American guitars and British amps.
If you’ve been on the path of this spring’s Rhett Schull/Zach Person tour, you’ve been treated to one of the coolest rock ’n’ roll double bills criss-crossing North America this year. Person, who is based in Austin, put out his second full-length record, Let’s Get Loud, in March 2024, and it was packed with alt-, blues-, and psychedelic-rock anthems built around his take-no-prisoners playing.
This year, Person is road-doggin’ it around the United States as a two-piece unit with just a drummer, and PG’s Chris Kies caught up with him before he and Shull played the Eastside Bowl in Madison, Tennessee, to see what goods Person is bringing for this spring’s shows.
Brought to you by D’Addario
Customized Custom
This Gibson Jimi Hendrix 1967 Custom SG came from Gibson’s custom shop, and for Person, an SG with humbuckers is a hard combination to beat. He removed the Maestro trem system and had a tailpiece installed for tuning stability on the road, and he subjected the neck humbucker to a “Jimmy Page mod,” which entails removing the pole pieces to get closer to single-coil tones. This SG stays in standard tuning, with Ernie Ball or D’Addario strings (usually .010–.046s). Person digs Dunlop Flow Grip .88 mm picks.
Brown Sound
Person brought this 1967 Gibson SG Special back to life with a list of modifications and upgrades, including new pickups and a refinish, but its wood, neck shape, and original frets all made it worth it to him. The neck shape is narrow but chunky in Person’s hands, landing somewhere near the feel of Tyler Bryant’s 1962 Stratocaster. The pickups now are OX4 P-90s, and like the Custom, this one’s had its Maestro system amputated.
Jeannie Comes Alive
One Thanksgiving at his in-laws’ home in Dallas, Person mentioned how badly he wanted a Gibson LG-2 acoustic. As it happened, his father-in-law suspected his mother had one, which had been relegated to storage in a shed. Person and his wife’s father ventured through rain to dig it out, and sure enough, a very beat up LG-1 was withering away in its case. No local techs in Austin thought it was worth saving, except for Elaine Filion, who was used to taking on bigger restoration projects. Filion succeeded, taking the top off and installing an X-bracing system to turn the LG-1 into an LG-2-style guitar. Now, it’s got an L.R. Baggs pickup and bears the nameplate “Jeannie” on its headstock to commemorate his wife’s grandma, the original owner. Jeannie usually stays home, but Person brought her out specially for the Rundown.
Marshall Muscle
This Marshall JTM45 MkII is Person’s usual go-to. It runs just at breakup volume and gets pushed with some variation of a Pro Co RAT, his favorite dirt box.
Supro Signature
This Super Black Magick Reverb, Tyler Bryant’s signature, is along for the ride as a backup to the Marshall.
Zach Person’s Pedalboard
Person has done tours with just an overdrive pedal and nothing else, so by comparison, this two-tiered Vertex board is luxurious. Still, it’s compact and carries all he needs at the moment. The JHS Pack Rat is the core sound, set fairly heavy and dirty. The rest includes a Boss TU-3, EarthQuaker Devices Double Hoof, Vox Clyde McCoy wah, Boss BF-2, DigiTech Drop, Strymon El Capistan, and an Interstellar Audio Machines Marsling Octafuzzdrive. A TC Helicon Mic Mechanic rides along as a vocal effect so Person can keep control over his voice from night to night.