
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]
Onstage, Tommy Emmanuel executes a move that is not from the playbook of his hero, Chet Atkins.
Recorded live at the Sydney Opera House, the Australian guitarist’s new album reminds listeners that his fingerpicking is in a stratum all its own. His approach to arranging only amplifies that distinction—and his devotion to Chet Atkins.
Australian fingerpicking virtuoso Tommy Emmanuel is turning 70 this year. He’s been performing since he was 6, and for every solo show he’s played, he’s never used a setlist.
“My biggest decision every day on tour is, ‘What do I want to start with? How do I want to come out of the gate?’” Emmanuel explains to me over a video call. “A good opener has to have everything. It has to be full of surprise, it has to have lots of good ideas, lots of light and shade, and then, hit it again,” he says, illustrating each phrase with his hands and ending with a punch.“You lift off straightaway with the first song, you get airborne, you start reaching, and then it’s time to level out and take people on a journey.”
In May 2023, Emmanuel played two shows at the Sydney Opera House, the best performances from which have been combined on his new release, Live at the Sydney Opera House. The venue’s Concert Hall, which has a capacity of 2,679, is a familiar room for Emmanuel, but I think at this point in his career he wouldn’t bring a setlist if he was playing Wembley Stadium. On the recording, Emmanuel’s mind-blowingly dexterous chops, distinctive attack and flair, and knack for culturally resonant compositions are on full display. His opening song for the shows? An original, “Countrywide,” with a segue into Chet Atkins’ “El Vaquero.”
“When I was going to high school in the ’60s, I heard ‘El Vaquero’ on Chet Atkins’ record, [1964’s My Favorite Guitars],” Emmanuel shares. “And when I wrote ‘Countrywide’ in around ’76 or ’77, I suddenly realized, ‘Ah! It’s a bit like “El Vaquero!”’ So I then worked out ‘El Vaquero’ as a solo piece, because it wasn’t recorded like that [by Atkins originally].
“The co-writer of ‘El Vaquero’ is Wayne Moss, who’s a famous Nashville session guy who played ‘da da da’ [sings the guitar riff from Roy Orbison’s ‘Pretty Woman’]. And he played on a lot of Chet’s records as a rhythm guy. So once when I played ‘El Vaquero’ live, Wayne Moss came up to me and said, ‘You know, you did my part and Chet’s at the same time. That’s not fair!’” Emmanuel says, laughing.
Atkins is the reason Emmanuel got into performing. His mother had been teaching him rhythm guitar for a couple years when he heard Atkins on the radio and, at 6, was able to immediately mimic his fingerpicking technique. His father recognized Emmanuel’s prodigious talent and got him on the road that year, which kicked off his professional career. He says, “By the time I was 6, I was already sleep-deprived, working too hard, and being forced to be educated. Because all I was interested in was playing music.”
Emmanuel talks about Atkins as if the way he viewed him as a boy hasn’t changed. The title Atkins bestowed upon him, C.G.P. (Certified Guitar Player), appears on Emmanuel’s album covers, in his record label (C.G.P. Sounds), and is inlaid at the 12th fret on his Maton Custom Shop TE Personal signature acoustic. (Atkins named only five guitarists C.G.P.s. The others are John Knowles, Steve Wariner, Jerry Reed, and Atkins himself.) For Emmanuel, even today most roads lead to Atkins.
When I ask Emmanuel about his approach to arranging for solo acoustic guitar, he says, “It was really hit home for me by my hero, Chet Atkins, when I read an interview with him a long time ago and he said, ‘Make your arrangement interesting.’ And I thought, ‘Wow!’ Because I was so keen to be true to the composer and play the song as everyone knows it. But then again, I’m recreating it like everyone else has, and I might as well get in line with the rest of them and jump off the cliff into nowhere. So it struck me: ‘How can I make my arrangements interesting?’ Well, make them full of surprises.”
When Emmanuel was invited to contribute to 2015’s Burt Bacharach: This Guitar’s in Love with You, featuring acoustic-guitar tributes to Bacharach’s classic compositions by various artists, Emmanuel expresses that nobody wanted to take “(They Long to Be) Close to You,” due to its “syrupy” nature. But for Emmanuel, this presented an entertaining challenge.
He explains, “I thought, ‘Okay, how can I reboot “Close to You?’ So even the most jaded listener will say, ‘Holy fuck—I didn’t expect that! Wow, I really like that; that is a good melody!’ So I found a good key to play the song in, which allowed me to get some open notes that sustain while I move the chords. Then what I did is, in every phrase, I made the chord unresolve, then resolve.
Tommy Emmanuel's Gear
“I’m writing music for the film that’s in my head,” Emmanuel says. “So, I don’t think, ‘I’m just the guitar,’ ever.”
Photo by Simone Cecchetti
Guitars
- Three Maton Custom Shop TE Personals, each with an AP5 PRO pickup system
Amps
- Udo Roesner Da Capo 75
Effects
- AER Pocket Tools preamp
Strings & Picks
- Martin TE Signature Phosphor Bronze (.012–.054)
- Martin SP strings
- Ernie Ball Paradigm strings
- D’Andrea Pro Plec 1.5 mm
- Dunlop medium thumbpicks
“And then to really put the nail in the coffin, at the end, ‘Close to you’ [sings melody]. I finished on a major 9 chord which had that note in it, but it wasn’t the key the song was in, which is a typical Stevie Wonder trick. All the tricks I know, the wonderful ideas that I’ve stolen, are from Michael Jackson, Stevie Wonder, Lionel Richie, James Taylor, Carole King, Neil Diamond. All of the people who wrote really incredibly great pop songs and R&B music—I stole every idea I could, and I tried to make my little two-and-a -half minutes as interesting and entertaining as possible. Because entertainment equals: Surprise me.”
I share with Emmanuel that the performances on Live at the Sydney Opera House, which include his popular “Beatles Medley,” reminded me of another possible arrangement trick. In Harpo Marx’s autobiography, Harpo Speaks, I preface, Marx writes of a lesson he learned as a performer—to “answer the audience’s questions.” (Emmanuel says he’s a big fan of the book and read it in the early ’70s.) That happened for me while listening to the medley, when, after sampling melodies from “She’s a Woman” and “Please Please Me,” Emmanuel suddenly lands on “While My Guitar Gently Weeps.”
I say, “I’m waiting for something that hits more recognizably to me, and when ‘While My Guitar’ comes in, that’s like answering my question.”
“It’s also Paul and John, Paul and John, George,” Emmanuel replies. “You think, ‘That’s great, that’s great pop music,’ then, ‘Wow! Look at the depth of this.’”Often Emmanuel’s flights on his acoustic guitar are seemingly superhuman—as well as supremely entertaining.
Photo by Ekaterina Gorbacheva
A trick I like to employ as a writer, I say to Emmanuel, is that when I’m describing something, I’ll provide the reader with just enough context so that they can complete the thought on their own.
“You can do that musically as well,” says Emmanuel. He explains how, in his arrangement of “What a Wonderful World,” he’ll play only the vocal melody. “When people are asking me at a workshop, ‘How come you don’t put chords behind that part?’ I say, ‘I’m drawing the melody and you’re putting in all the background in your head. I don’t need to tell you what the chords are. You already know what the chords are.’”
“Wayne Moss came up to me and said, ‘You know, you did my part and Chet’s at the same time. That’s not fair!’”
Another track featured on Live at the Sydney Opera House is a cover of Paul Simon’s “American Tune” (which Emmanuel then jumps into an adaptation of the Australian bush ballad, “Waltzing Matilda”). It’s been a while since I really spent time with There GoesRhymin’ Simon (on which “American Tune” was first released), and yet it sounded so familiar to me. A little digging revealed that its melody is based on the 17th-century Christian hymn, “O Sacred Head, Now Wounded,” which was arranged and repurposed by Bach in a few of the composer’s works. The cross-chronological and genre-lackadaisical intersections that come up in popular music sometimes is fascinating.
“I think the principle right there,” Emmanuel muses, “is people like Bach and Beethoven and Mozart found the right language to touch the heart of a human being through their ears and through their senses ... that really did something to them deep in their soul. They found a way with the right chords and the right notes, somehow. It could be as primitive as that.
Tommy Emmanuel has been on the road as a performing guitarist for 64 years. Eat your heart out, Bob Dylan.
Photo by Jan Anderson
“It’s like when you’re a young composer and someone tells you, ‘Have a listen to Elton John’s “Candle in the Wind,”’ he continues. “‘Listen to how those notes work with those chords.’ And every time you hear it, you go, ‘Why does it touch me like that? Why do I feel this way when I hear those chords—those notes against those chords?’ I say, it’s just human nature. Then you wanna go, ‘How can I do that!’” he concludes with a grin.
“You draw from such a variety of genres in your arrangements,” I posit. “Do you try to lean into the side of converting those songs to solo acoustic guitar, or the side of bridging the genre’s culture to that of your audience?”
“I stole every idea I could, and I tried to make my little two-and-a-half minutes as interesting and entertaining as possible. Because entertainment equals: Surprise me.”
“If I was a method actor,” Emmanuel explains, “what I’m doing is—I’m writing music for the film that’s in my head. So, I don’t think, ‘I’m just the guitar,’ ever. I always think it has to have that kind of orchestral, not grandeur, but … palette to it. Because of the influence of Stevie Wonder, Billy Joel, and Elton John, especially—the piano guys—I try to use piano ideas, like putting the third in the low bass a lot, because guitar players don’t necessarily do that. And I try to always do something that makes what I do different.
“I want to be different and recognizable,” he continues. “I remember when people talked about how some players—you just hear one note and you go, ‘Oh, that’s Chet Atkins.’ And it hit me like a train, the reason why a guy like Hank Marvin, the lead guitar player from the Shadows.... I can tell you: He had a tone that I hear in other players now. Everyone copied him—they just don’t know it—including Mark Knopfler, Eric Clapton, Jimmy Page, all those people. I got him up to play with me a few times when he moved to Australia, and even playing acoustic, he still had that sound. I don’t know how he did it, but it was him. He invented himself.”
YouTube It
Emmanuel performs his arrangement of “What a Wonderful World,” illustrating how omitting a harmonic backdrop can have a more powerful effect, especially when playing such a well-known melody.
Featuring a newly-voiced circuit with more compression and versatility, these pedals are hand-crafted in Los Angeles for durability.
Messiah Guitars custom shop has launched a pair of new pedals: The Eddie Boostdrive Session Edition and Lil’ Ed Session Drive.
The two pedals are full-size and mini-sized versions of a newly-voiced circuit based on Messiah’s successful Eddie Boostdrive. The two new “Session” pedals feature more compression and versatility in the overall tone, and showcase Messiah’s ongoing collaboration with Nashville session guitarist Eddie Haddad.
The new Session Boostdrive schematic includes a fine-tuned EQ section (eliminating the need for the Tight switch on the earlier Boostdrive) and two independently operated circuits: a single-knob booster, and a dual-mode drive featuring a 3-band EQ. The booster consists of a single-stage MOSFET transistor providing boost ranging from -3dB to 28dB. At low settings, the boost adds sparkle to the tone, while a fully cranked setting will send your amp to a fuzzy territory. Thebooster engagement is indicated by a purple illuminated foot switch.
The overdrive contains a soft-clipped op-amp stage, inspired by a screamer-style circuit. The pedal includes a classic Silicon clipping mode (when activated, the pedal’s indicator light is blue)and an LED mode for a more open, amp-like break up (indicator light is red).
The active 3-band EQ is highly interactive and capable of emulating many popular drive sounds. Although both effects can be used separately, engaging them simultaneously produces juicy tones that will easily cut through the mix. Both new pedals accept a standard 9V pedal power supply with negative center pin.
“I love my original Boostdrive,” says Haddad, “but I wanted to explore the circuit and see if we could give it more focused features. This would make it more straightforward for guitarists who prefer simplicity in their drive pedals. The boost is super clean and loud in all the right ways…it can instantly sweeten up an amp and add more heft and sparkle to the drive section.”
Like their custom guitars and amplifiers, Messiah’s pedals are hand-crafted in Los Angeles for durability and guaranteed quality.
The Lil’ Ed Session Drive pedal includes:
- 5-knob controls, a 2-way mode side switch
- Durable, space-saving cast aluminum alloy 1590A enclosure with fun artwork
- True bypass foot switch
- Standard 9V/100mA pedal power input
The Eddie Session Edition pedal features:
- 6-knob controls, a 2-way mode switch; space-saving top-side jacks
- Durable, cast aluminum alloy 125B enclosure with fun artwork
- Easy to see, illuminated optical true bypass foot switches
- Standard 9V/100mA pedal power input
The Eddie Boostdrive Session Edition retails for $249.00, and the Lil’ Ed Session Drive for$179.
For more information, please visit messiahguitars.com.
Eddie BoostDrive and Lil' Ed pedal review with Eddie & Jax - YouTube
Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.Joe Glaser has been a pillar of Nashville's guitar community for decades. He's a man that dreams in mechanical terms often coming up ideas while deep in a REM cycle. Through his various companies he's designed, developed, and released a handful of "blue water" solutions to age-old instrument problems making the tolerable terrific. In this comprehensive visit to Glaser's home base, we get up close and personal with several of the products that enhance intonation and playability without disrupting the guitar's integrity.
In addition, Music City Bridge CEO Joshua Rawlings introduces us to a couple software ventures. Shop Flow helps increase productivity and efficiency for guitar builders and repair shops, while Gear Check aims to help guitarist's keep track of their collection and its history. Join John Bohlinger as he goes inside this inconspicuous six-string sanctuary.
With 700 watts of power, built-in overdrive, versatile EQ options, and multiple output choices, this bass head is designed to deliver unparalleled clarity and performance in a lightweight, rugged package.
PowerStage 700 Bass is compact and durable for easy transport yet powerful enough to fill any venue. This world-class bass head can also serve as the ideal clean power platform to amplify your preamp or modeler. Streamline your rig without compromising your sound and focus on what truly matters—your music.
Designed by Seymour Duncan’s legendary engineer Kevin Beller, a lifelong bass player, this 700-watt bass head delivers unparalleled clarity and performance in a lightweight, rugged package. Whether plugging in on stage or in the studio, PowerStage 700Bass provides tight low-end and rich harmonics, with a footswitchable built-in overdrive for an extra layer of sonic versatility.
A robust, bass-optimized EQ (treble, low mid, high mid, bass and presence) tailors your sound to any room. Need to switch between active and passive basses? You’re covered - PowerStage700 Bass includes a convenient -10db pad control. Multiple output options (¼”, Speakon, XLRDI, and headphone) work for any setup, whether powering cabinets, going direct to a PA, or recording straight into your audio interface.
- 700 Watts of Power at 4 ohms• Preamp voiced for a wide range of vintage & amp; modern bass sounds
- Built-in Overdrive that can go from a light vintage saturation to full-throttle bone-grinding distortion (with optional foot-switchable control)
- Effects loop allows for post-preamp processing and easy integration with modelers and preamp pedals
- 4 band EQ, Sweepable mid controls, and presence button offer dynamic tone shaping possibilities
- Aux input
- Super lightweight and durable chassis for easy transport with our optional gig bag or rack ears.
For more information, please visit seymourduncan.com.