What exactly is bias? Bias is prejudice in favor of or against … oh wait, wrong kind of bias. I think he wanted me to write about bias in a tube amplifier, which is far less polarizing.
Bias, as defined in the RCA Radiotron Designers Handbook, is “voltage applied to the grid [of a tube] to obtain a desired operating point.” Well, that is the most basic explanation, but for the most part it is good enough and pertains to the majority of tube output stages in our favorite tube guitar amps.
Setting the bias adjustment controls to these listed voltages in no way guarantees that your amp is properly biased.
Besides “applying” a voltage to a vacuum tube, however, biasing can occur in another way as well. There are quite a few amplifiers, such as a Vox AC15 and AC30, any of my Budda and EAST designs, and even most of the early, low-wattage amplifiers of the tweed era that use what’s known as a “cathode bias” design. This is where the current flowing through the tube (which attains the aforementioned “desired operating point”) is not set by the voltage “applied” to the grid of the tube, but is instead set by the resistor in the cathode leg of the tube. It’s a bit more complicated than that, but the result is an amplifier whose output stage is “self-biasing.”
Most amplification devices, including transistors and even preamp tubes, need to be “biased” in order to perform properly, but this type of biasing is fixed in the design parameters of the circuit. In the case of the preamp tubes in your guitar amp, bias is based on the value of the cathode resistor, among other things. But that’s enough design theory for today. Let’s get back to the core task of biasing the output tubes in most guitar amplifiers.
First, the bias voltages you see listed on many schematics, such as 52V on a black-panel Fender Twin Reverb or 51V on a Marshall 100W Super Lead schematic, are merely approximations of the voltages that should be expected in that area of the circuit. Setting the bias adjustment controls to these listed voltages in no way guarantees that your amp is properly biased. Tube bias is also dependent on the high voltage (or B+) applied to the plate of the output tube, which can vary within tolerances of the transformers as well as in the AC line voltage fed to the amp. (This is why amps can sometimes sound better in one room or club than others.)
But even more important to understand is that tubes produced in different factories across the globe will bias up differently! What I mean by this is, if you properly bias a set of output tubes—let’s say 6L6s made in Russia—and then you swap them out with a set made in China, in the same amplifier without changing the setting of the bias control, the end result will almost always be a different bias reading. This is why it’s always best to have checked and reset the bias whenever output tubes are replaced. Now, how do we do that?
The Preferred Method
Fig. 1
There are several different ways to measure output-tube bias current at idle. The safest method is to use what is commonly called a bias probe (Fig. 1). This is a device that is inserted between an output tube and its socket. (I typically make my own bias probes, but if you simply search “bias probe” online, you’ll find plenty to choose from. If you already own a multimeter, you can simply purchase the probes, but there are also options to purchase a full system with either a digital or analog meter, should you need it.) This device breaks the connection between the cathode (which is the metallic electrode from which electrons are emitted into the tube) of the tube and its ground connection, and inserts a small value resistor in between. It then allows the voltage across the resistor to be read. The resistor is typically 1 ohm and the resulting voltage drop across it is in millivolts (mV), so no chance of shock here. This provides a true and accurate measurement of the actual current flowing through one tube. Then, you set your bias and you’re done!
But even more important to understand is that tubes produced in different factories across the globe will bias up differently!
Ah, but wait! How do you set your bias? Let’s learn a bit more. Most tube amplifiers, if they are not cathode-biased designs, have some way to adjust the output-tube bias. One longstanding exception to this are most Mesa/Boogie amps. The bias voltage in these amps is not adjustable, which is why Mesa suggests only purchasing their tubes for their amps, because they are designed to fall within the acceptable bias range for their amps. This adds a certain degree of confidence for owner servicing, although, of course, it limits your options.
Let’s take a look, however, at a typical Fender or Marshall bias control. Most older Fenders have a pot with a slot for a screwdriver mounted to the chassis in the area of the power or mains transformer, while most older Marshalls have their bias pot mounted on the circuit board. (You might want to go online to look at schematics for your amp to help you find it.) Either way, this is where you’ll make your adjustment.
To get started, you’ll most likely need to pull the chassis and place it in a stable work environment. Insert the bias probe device between one of the tubes and the socket (Fig. 2). Make sure all the volume controls are set to zero, turn the amp on, and let the tubes warm up. It’s also good to try to have a load on the speaker jack—whether a speaker or an appropriate resistor or load box. This is not 100 percent necessary for just setting the bias to a particular number, but sound checking is one of the ways I like to make the final adjustments, so being able to connect the speaker to the chassis while it’s on the bench is certainly a necessity for me.
Now, where to set the numbers? There are certainly more than a few opinions floating around on the interwebs about what optimal bias settings are. Some engineering types will tout 50 percent maximum plate dissipation or 70 percent maximum dissipation, and while it may look good or make sense on paper, I’ve heard the result of guitar amplifiers designed by the book to optimal specifications … and to me they sound, well, less than optimal. It may work in the hi-fi world, where perfect sound reproduction is the goal, but guitar amplifiers are in the sound production business, so it’s a bit different. (In the most basic terms, maximum plate dissipation is the amount of power the plate of the tube is designed to deliver.)
Different types of output tubes have their own acceptable range of bias current. There are so many variables at play that there is no “correct” number. The plate voltage in the amplifier, the output transformer’s primary impedance, and the country of origin of a tube all factor into how it interacts with the voltage and output transformer to define what the optimal bias current will be. Below are the average ranges for some typical octal output tubes:
• 6L6: 25–35 mA
• EL34: 30–40 mA
• 6V6: 18–25 mA
• 6550: 35–45 mA
• KT66: 30–40 mA
Fig. 3
These should be the ranges in which these tubes will perform and sound the best, and they can be accurately measured with a digital multimeter. The best way for you to decide what setting is best for you is a combination of the reading on the meter and your ears! Using the bias control, set the bias to somewhere in the ranges given above (Fig. 3) and play the amp. Note: Some amps will act funny and develop horrible noises (parasitic oscillations) when a bias probe is in place while the amp is being played. If this is the case, you’ll need to remove the bias probe each time you play the amp.)
Move the setting a couple mA in one direction or the other and play again. Don’t expect extreme changes; that’s not what we’re looking for. Listen for subtle differences. Is one setting a little more or less harsh? Is the bottom end too soft or flubby? Is the amp as clean as you want it? Sometimes these little subtleties are what make one amp sound and feel better than another!
Most older Fenders have a pot with a slot for a screwdriver mounted to the chassis in the area of the power or mains transformer, while most older Marshalls have their bias pot mounted on the circuit board.
Also, you should be doing this at the volume you would typically use onstage or in the studio. You may not notice much change if your volume is at 1, but you want to optimize the amp for the way you will be using it.
Eyes Wide Open
Fig. 4
Knowing the ballpark bias numbers is good, and adding your ears is even better, but I also like to see what I’m hearing, so I always incorporate an oscilloscope when I’m setting the bias on an amp. I mentioned crossover distortion above, and when it comes to setting up amps for today’s pedal-hungry players, I find that setting the bias to where there is just a hint of crossover distortion at full output is what works best. Fig. 4 is what that looks like on the oscilloscope. This keeps the amp very clean and makes most pedal users happy.
By the way, here’s a mini primer in crossover distortion. In a push-pull output stage, which is found in most amplifiers with two or more output tubes, each tube (or pair of tubes) is responsible for amplifying at least half of the audio signal. If the tubes are not biased properly, one tube (or pair) will stop amplifying before the other tube (or pair) start amplifying. This will create crossover distortion. Proper biasing will allow the two halves to interact correctly. It’s like a nice firm handshake between both halves.
Beware These Old-School Methods
Let’s look at a couple popular methods that I do not recommend, but are worth discussing because they are, nonetheless, common. The first is: With the amp off and output tubes removed, use a multimeter to measure the resistance of each half of the primary side of the output transformer. This would typically be from the center tap to each side of the primary winding.
In the most basic terms, a transformer is a bunch of wire wound around a steel core. On the primary side of an output transformer, the center tap is the electrical “middle” of this long length of wire. This is typically where the high voltage is applied. The ends of this length of wire are connected to the plates of the tube, thereby applying the high voltage to the tubes. As an example, typically in most Fender amps, the center tap is red, and the ends of the primary windings are blue and brown.
Fig. 5
Next, install the output tubes, turn the amp on, and measure the voltage drop across each half of the output transformer with the amp at idle in operational mode (Fig. 5). Voltage divided by resistance will give you the DC current through the tubes. For example, 1.17V / 15.8R = 0.074, or 74 mA. The numbers I used here were actual measurements in one side (one half) of a 100W amp using four output tubes (two per side). So, divide the 74 mA by two, and you get an average of 37 mA per tube.
Next, you can try the shunt method. This requires a multimeter that can read DC current in milliamps (mA). Connect one meter lead to the center tap of the output transformer and the other lead to the output transformer’s primary side. Typically, in most amps using octal tubes (6L6, 6V6, EL34, 6550, KT88, etc.), this will be pin 3 on any output tube socket. Turn the amp on and, in operating mode at idle (i.e., volume off), measure the current across that half of the output transformer. For example, if your measurement is 72 mA and it’s an amp that utilizes four output tubes, the current measured is for two of those tubes, so once again divide by two to arrive at 36 mA per tube.
I’ve heard the result of guitar amplifiers designed by the book to optimal specifications … and to me they sound, well, less than optimal.
Both of those methods are very old school and still in practice, but I wouldn’t use either for two reasons: 1) I don’t believe they’re very accurate, and 2) they’re dangerous! You’re probing around inside the high voltage area of the amp, and one slip will either take out a fuse, take out a tube, take out your meter, or, worse case, let you know exactly what 450V DC feels like! So, although these methods are used, let’s just say no here.
Some Personal Insights
I’d also like to add a little personal experience to this procedure, based on decades in the biz. Back in the day, when I began servicing and modifying gear, guitarists were regularly playing 50- and 100-watt amps. (Everybody looked at me like I had three heads when I came out with the 18-watt Budda Twinmaster, but that’s a whole other story.) There were some overdrive and distortion pedals around (now all vintage), but certainly not the pedal proliferation we have now, so players were pretty much guitar, cable, amp … go! In these situations, I would most times run the tubes with a pretty hot bias so the amp would be fatter and overdrive a bit earlier and easier, as a decent percentage of the overdrive was developed by pushing the output tubes. As time went on, output attenuators became more popular, so amps could be pushed hard, but at more manageable volume levels. That was still a good scenario for a hotter bias of the output tubes in high-power amps. Eventually, players started playing lower-power amps, so they could open them up and get great output-tube distortion at lesser volumes. The problem is that hotter-biased low-power amps tend to get mushy and have less definition when pushed hard, so a more moderate bias setting is preferred here—just enough so there is no crossover distortion. Move up to today’s scenario and you’ll find that almost all overdrive and/or distortion is typically coming from a pedal. In that case, an amp is nothing more than an amplification device for pedals.
So, that’s what I’ve learned about tube-biasing from my decades of experience. But the bottom line is, there is no absolute right or wrong settings when it comes to biasing an amp. Keep your ears open and go with what sounds best to you.
Keith Urban’s first instrument was a ukulele at age 4. When he started learning guitar two years later, he complained that it made his fingers hurt. Eventually, he came around. As did the world.
He’s in the Songwriters Hall of Fame. He’s won 13 Country Music Association Awards, nine CMT video awards, eight ARIA (Australian Recording Industry Association) Awards, four American Music Awards, and racked up BMI Country Awards for 25 different singles.
He’s been a judge on American Idol and The Voice. In conjunction with Yamaha, he has his own brand of affordably priced Urban guitars and amps, and he has posted beginner guitar lessons on YouTube. His 2014 Academy of Country Music Award-winning video for “Highways Don’t Care” featured Tim McGraw and Keith’s former opening act, Taylor Swift. Add his marriage to fellow Aussie, the actress Nicole Kidman, and he’s seen enough red carpet to cover a football field.
Significantly, his four Grammys were all for Country Male Vocal Performance. A constant refrain among newcomers is, “and he’s a really good guitar player,” as if by surprise or an afterthought. Especially onstage, his chops are in full force. There are country elements, to be sure, but rock, blues, and pop influences like Mark Knopfler are front and center.
Unafraid to push the envelope, 2020’s The Speed of Now Part 1 mixed drum machines, processed vocals, and a duet with Pink with his “ganjo”—an instrument constructed of a 6-string guitar neck on a banjo body—and even a didgeridoo. It, too, shot to No. 1 on the Billboard Country chart and climbed to No. 7 on the pop chart.
His new release, High, is more down-to-earth, but is not without a few wrinkles. He employs an EBow on “Messed Up As Me” and, on “Wildfire,” makes use of a sequencerreminiscent of ZZ Top’s “Legs.” Background vocals in “Straight Lines” imitate a horn section, and this time out he duets on “Go Home W U” with rising country star Lainey Wilson. The video for “Heart Like a Hometown” is full of home movies and family photos of a young Urban dwarfed by even a 3/4-size Suzuki nylon-string.
Born Keith Urbahn (his surname’s original spelling) in New Zealand, his family moved to Queensland, Australia, when he was 2. He took up guitar at 6, two years after receiving his beloved ukulele. He released his self-titled debut album in 1991 for the Australian-only market, and moved to Nashville two years later. It wasn’t until ’97 that he put out a group effort, fronting the Ranch, and another self-titled album marked his American debut as a leader, in ’99. It eventually went platinum—a pattern that’s become almost routine.
The 57-year-old’s celebrity and wealth were hard-earned and certainly a far cry from his humble beginnings. “Australia is a very working-class country, certainly when I was growing up, and I definitely come from working-class parents,” he details. “My dad loved all the American country artists, like Johnny Cash, Haggard, Waylon. He didn’t play professionally, but before he got married he played drums in a band, and my grandfather and uncles all played instruments.
One of Urban’s biggest influences as a young guitar player was Mark Knopfler, but he was also mesmerized by lesser-known session musicians such as Albert Lee, Ian Bairnson, Reggie Young, and Ray Flacke. Here, he’s playing a 1950 Broadcaster once owned by Waylon Jennings that was a gift from Nicole Kidman, his wife.
“For me, it was a mix of that and Top 40 radio, which at the time was much more diverse than it is now. You would just hear way more genres, and Australia itself had its own, what they call Aussie pub rock—very blue-collar, hard-driving music for the testosterone-fueled teenager. Grimy, sweaty, kind of raw themes.”
A memorable event happened when he was 7. “My dad got tickets for the whole family to see Johnny Cash. He even bought us little Western shirts and bolo ties. It was amazing.”
But the ukulele he was gifted a few years earlier, at the age of 4, became a constant companion. “I think to some degree it was my version of the stuffed animal, something that was mine, and I felt safe with it. My dad said I would strum it in time to all the songs on the radio, and he told my mom, ‘He’s got rhythm. I wonder what a good age is for him to learn chords.’ My mom and dad ran a little corner store, and a lady named Sue McCarthy asked if she could put an ad in the window offering guitar lessons. They said, ‘If you teach our kid for free, we’ll put your ad in the window.’”
Yet, guitar didn’t come without problems. “With the guitar, my fingers hurt like hell,” he laughs, “and I started conveniently leaving the house whenever the guitar teacher would show up. Typical kid. I don’t wanna learn, I just wanna be able to do it. It didn’t feel like any fun. My dad called me in and went, ‘What the hell? The teacher comes here for lessons. What’s the problem?’ I said I didn’t want to do it anymore. He just said, ‘Okay, then don’t do it.’ Kind of reverse psychology, right? So I just stayed with it and persevered. Once I learned a few chords, it was the same feeling when any of us learn how to be moving on a bike with two wheels and nobody holding us up. That’s what those first chords felt like in my hands.”
Keith Urban's Gear
Urban has 13 Country Music Association Awards, nine CMT video awards, eight ARIA Awards, and four Grammys to his name—the last of which are all for Best Country Male Vocal Performance.
Guitars
For touring:
- Maton Diesel Special
- Maton EBG808TE Tommy Emmanuel Signature
- 1957 Gibson Les Paul Junior, TV yellow
- 1959 Gibson ES-345 (with Varitone turned into a master volume)
- Fender 40th Anniversary Tele, “Clarence”
- Two first-generation Fender Eric Clapton Stratocasters (One is black with DiMarzio Area ’67 pickups, standard tuning. The other is pewter gray, loaded with Fralin “real ’54” pickups, tuned down a half-step.)
- John Bolin Telecaster (has a Babicz bridge with a single humbucker and a single volume control. Standard tuning.)
- PRS Paul’s Guitar (with two of their narrowfield humbuckers. Standard tuning.)
- Yamaha Keith Urban Acoustic Guitar (with EMG ACS soundhole pickups)
- Deering “ganjo”
Amps
- Mid-’60s black-panel Fender Showman (modified by Chris Miller, with oversized transformers to power 6550 tubes; 130 watts)
- 100-watt Dumble Overdrive Special (built with reverb included)
- Two Pacific Woodworks 1x12 ported cabinets (Both are loaded with EV BlackLabel Zakk Wylde signature speakers and can handle 300 watts each.)
Effects
- Two Boss SD-1W Waza Craft Super Overdrives with different settings
- Mr. Black SuperMoon Chrome
- FXengineering RAF Mirage Compressor
- Ibanez TS9 with Tamura Mod
- Boss BD-2 Blues Driver
- J. Rockett Audio .45 Caliber Overdrive
- Pro Co RAT 2
- Radial Engineering JX44 (for guitar distribution)
- Fractal Audio Axe-Fx XL+ (for acoustic guitars)
- Two Fractal Audio Axe-Fx III (one for electric guitar, one for bass)
- Bricasti Design Model 7 Stereo Reverb Processor
- RJM Effect Gizmo (for pedal loops)
(Note: All delays, reverb, chorus, etc. is done post amp. The signal is captured with microphones first then processed by Axe-Fx and other gear.)
- Shure Axient Digital Wireless Microphone System
Strings & Picks
- D’Addario NYXL (.011–.049; electric)
- D’Addario EJ16 (.012–.053; acoustics)
- D’Addario EJ16, for ganjo (.012–.053; much thicker than a typical banjo strings)
- D’Addario 1.0 mm signature picks
He vividly remembers the first song he was able to play after “corny songs like ‘Mama’s little baby loves shortnin’ bread.’” He recalls, “There was a song I loved by the Stylistics, ‘You Make Me Feel Brand New.’ My guitar teacher brought in the sheet music, so not only did I have the words, but above them were the chords. I strummed the first chord, and went, [sings E to Am] ‘My love,’ and then minor, ‘I'll never find the words, my,’ back to the original chord, ‘love.’ Even now, I get covered in chills thinking what it felt like to sing and put that chord sequence together.”
After the nylon-string Suzuki, he got his first electric at 9. “It was an Ibanez copy of a Telecaster Custom—the classic dark walnut with the mother-of-pearl pickguard. My first Fender was a Stratocaster. I wanted one so badly. I’d just discovered Mark Knopfler, and I only wanted a red Strat, because that’s what Knopfler had. And he had a red Strat because of Hank Marvin. All roads lead to Hank!”
He clarifies, “Remember a short-lived run of guitar that Fender did around 1980–’81, simply called ‘the Strat’? I got talked into buying one of those, and the thing weighed a ton. Ridiculously heavy. But I was just smitten when it arrived. ‘Sultans of Swing’ was the first thing I played on it. ‘Oh my god! I sound a bit like Mark.’”
“Messed Up As Me” has some licks reminiscent of Knopfler. “I think he influenced a huge amount of my fingerpicking and melodic choices. I devoured those records more than any other guitar player. ‘Tunnel of Love,’ ‘Love over Gold,’ ‘Telegraph Road,’ the first Dire Straits album, and Communique. I was spellbound by Mark’s touch, tone, and melodic choice every time.”
Other influences are more obscure. “There were lots of session guitar players whose solos I was loving, but had no clue who they were,” he explains. “A good example was Ian Bairnson in the Scottish band Pilot and the Alan Parsons Project. It was only in the last handful of years that I stumbled upon him and did a deep dive, and realized he played the solo on ‘Wuthering Heights’ by Kate Bush, ‘Eye in the Sky’ by Alan Parsons, ‘It’s Magic’ and ‘January’ by Pilot—all these songs that spoke to me growing up. I also feel like a lot of local-band guitar players are inspirations—they certainly were to me. They didn’t have a name, the band wasn’t famous, but when you’re 12 or 13, watching Barry Clough and guys in cover bands, it’s, ‘Man, I wish I could play like that.’”
On High, Urban keeps things song-oriented, playing short and economical solos.
In terms of country guitarists, he nods, “Again, a lot of session players whose names I didn’t know, like Reggie Young. The first names I think would be Albert Lee and Ray Flacke, whose chicken pickin’ stuff on the Ricky Skaggs records became a big influence. ‘How is he doing that?’”
Flacke played a role in a humorous juxtaposition. “I camped out to see Iron Maiden,” Urban recounts. “They’d just put out Number of the Beast, and I was a big fan. I was 15, so my hormones were raging. I’d been playing country since I was 6, 7, 8 years old. But this new heavy metal thing is totally speaking to me. So I joined a heavy metal band called Fractured Mirror, just as their guitar player. At the same time, I also discovered Ricky Skaggs and Highways and Heartaches. What is this chicken pickin’ thing? One night I was in the metal band, doing a Judas Priest song or Saxon. They threw me a solo, and through my red Strat, plugged into a Marshall stack that belonged to the lead singer, I shredded this high-distortion, chicken pickin’ solo. The lead singer looked at me like, ‘What the fuck are you doing?’ I got fired from the band.”
Although at 15 he “floated around different kinds of music and bands,” when he was 21 he saw John Mellencamp. “He’d just put out Lonesome Jubilee. I’d been in bands covering ‘Hurts So Good,' ‘Jack & Diane,’ and all the early shit. This record had fiddle and mandolin and acoustic guitars, wall of electrics, drums—the most amazing fusion of things. I saw that concert, and this epiphany happened so profoundly. I looked at the stage and thought, ‘Whoa! I get it. You take all your influences and make your own thing. That’s what John did. I’m not gonna think about genre; I’m gonna take all the things I love and find my way.’
“Of course, getting to Nashville with that recipe wasn’t going to fly in 1993,” he laughs. “Took me another seven-plus years to really start getting some traction in that town.”
Urban’s main amp today is a Dumble Overdrive Reverb, which used to belong to John Mayer. He also owns a bass amp that Alexander Dumble built for himself.
Photo by Jim Summaria
When it comes to “crossover” in country music, one thinks of Glen Campbell, Kenny Rogers, Garth Brooks, and Dolly Parton’s more commercial singles like “Two Doors Down.” Regarding the often polarizing subject and, indeed, what constitutes country music, it’s obvious that Urban has thought a lot—and probably been asked a lot—about the syndrome. The Speed of Now Part 1 blurs so many lines, it makes Shania Twain sound like Mother Maybelle Carter. Well, almost.
“I can’t speak for any other artists, but to me, it’s always organic,” he begins. “Anybody that’s ever seen me play live would notice that I cover a huge stylistic field of music, incorporating my influences, from country, Top 40, rock, pop, soft rock, bluegrass, real country. That’s how you get songs like ‘Kiss a Girl’—maybe more ’70s influence than anything else.”
“I think [Mark Knopfler] influenced a huge amount of my fingerpicking and melodic choices. I devoured those records more than any other guitar player.”
Citing ’50s producers Chet Atkins and Owen Bradley, who moved the genre from hillbilly to the more sophisticated countrypolitan, Keith argues, “In the history of country music, this is exactly the same as it has always been. Patsy Cline doing ‘Walking After Midnight’ or ‘Crazy’; it ain’t Bob Wills. It ain’t Hank Williams. It’s a new sound, drawing on pop elements. That’s the 1950s, and it has never changed. I’ve always seen country like a lung, that expands outwards because it embraces new sounds, new artists, new fusions, to find a bigger audience. Then it feels, ‘We’ve lost our way. Holy crap, I don’t even know who we are,’ and it shrinks back down again. Because a purist in the traditional sense comes along, whether it be Ricky Skaggs or Randy Travis. The only thing that I think has changed is there’s portals now for everything, which didn’t used to exist. There isn’t one central control area that would yell at everybody, ‘You’ve got to bring it back to the center.’ I don’t know that we have that center anymore.”
Stating his position regarding the current crop of talent, he reflects, “To someone who says, ‘That’s not country music,’ I always go, “‘It’s not your country music; it’s somebody else’s country music.’ I don’t believe anybody has a right to say something’s not anything. It’s been amazing watching this generation actually say, ‘Can we get back to a bit of purity? Can we get real guitars and real storytelling?’ So you’ve seen the explosion of Zach Bryan and Tyler Childers who are way purer than the previous generation of country music.”
Seen performing here in 2003, Urban is celebrated mostly for his songwriting, but is also an excellent guitarist.
Photo by Steve Trager/Frank White Photo Agency
As for the actual recording process, he notes, “This always shocks people, but ‘Chattahoochee’ by Alan Jackson is all drum machine. I write songs on acoustic guitar and drum machine, or drum machine and banjo. Of course, you go into the studio and replace that with a drummer. But my very first official single, in 1999, was ‘It’s a Love Thing,’ and it literally opens with a drum loop and an acoustic guitar riff. Then the drummer comes in. But the loop never goes away, and you hear it crystal clear. I haven’t changed much about that approach.”
On the road, Urban utilizes different electrics “almost always because of different pickups—single-coil, humbucker, P-90. And then one that’s tuned down a half-step for a few songs in half-keys. Tele, Strat, Les Paul, a couple of others for color. I’ve got a John Bolin guitar that I love—the feel of it. It’s a Tele design with just one PAF, one volume knob, no tone control. It’s very light, beautifully balanced—every string, every fret, all the way up the neck. It doesn’t have a lot of tonal character of its own, so it lets my fingers do the coloring. You can feel the fingerprints of Billy Gibbons on this guitar. It’s very Billy.”
“I looked at the stage and thought, ‘Whoa! I get it. You take all your influences and make your own thing. I’m gonna take all the things I love and find my way.’”
Addressing his role as the collector, “or acquirer,” as he says, some pieces have quite a history. “I haven’t gone out specifically thinking, ‘I’m missing this from the collection.’ I feel really lucky to have a couple of very special guitars. I got Waylon Jennings’ guitar in an auction. It was one he had all through the ’70s, wrapped in the leather and the whole thing. In the ’80s, he gave it to Reggie Young, who owned it for 25 years or so and eventually put it up for auction. My wife wanted to give it to me for my birthday. I was trying to bid on it, and she made sure that I couldn’t get registered! When it arrived, I discovered it’s a 1950 Broadcaster—which is insane. I had no idea. I just wanted it because I’m a massive Waylon fan, and I couldn’t bear the thought of that guitar disappearing overseas under somebody’s bed, when it should be played.
“I also have a 1951 Nocaster, which used to belong to Tom Keifer in Cinderella. It’s the best Telecaster I’ve ever played, hands down. It has the loudest, most ferocious pickup, and the wood is amazing.”
YouTube
Urban plays a Gibson SG here at the 2023 CMT Music Awards. Wait until the end to see him show off his shred abilities.
Other favorites include “a first-year Strat, ’54, that I love, and a ’58 goldtop. I also own a ’58 ’burst, but prefer the goldtop; it’s just a bit more spanky and lively. I feel abundantly blessed with the guitars I’ve been able to own and play. And I think every guitar should be played, literally. There’s no guitar that’s too precious to be played.”
Speaking of precious, there are also a few Dumble amps that elicit “oohs” and “aahs.” “Around 2008, John Mayer had a few of them, and he wanted to part with this particular Overdrive Special head. When he told me the price, I said, ‘That sounds ludicrous.’ He said, ‘How much is your most expensive guitar?’ It was three times the value of the amp. He said, ‘So that’s one guitar. What amp are you plugging all these expensive guitars into?’ I was like, ‘Sold. I guess when you look at it that way.’ It’s just glorious. It actually highlighted some limitations in some guitars I never noticed before.”
“It’s just glorious. It actually highlighted some limitations in some guitars I never noticed before.”
Keith also developed a relationship with the late Alexander Dumble. “We emailed back and forth, a lot of just life stuff and the beautifully eccentric stuff he was known for. His vocabulary was as interesting as his tubes and harmonic understanding. My one regret is that he invited me out to the ranch many times, and I was never able to go. Right now, my main amp is an Overdrive Reverb that also used to belong to John when he was doing the John Mayer Trio. I got it years later. And I have an Odyssey, which was Alexander’s personal bass amp that he built for himself. I sent all the details to him, and he said, ‘Yeah, that’s my amp.’”
The gearhead in Keith doesn’t even mind minutiae like picks and strings. “I’ve never held picks with the pointy bit hitting the string. I have custom picks that D’Addario makes for me. They have little grippy ridges like on Dunlops and Hercos, but I have that section just placed in one corner. I can use a little bit of it on the string, or I can flip it over. During the pandemic, I decided to go down a couple of string gauges. I was getting comfortable on .009s, and I thought, ‘Great. I’ve lightened up my playing.’ Then the very first gig, I was bending the crap out of them. So I went to .010s, except for a couple of guitars that are .011s.”
As with his best albums, High is song-oriented; thus, solos are short and economical. “Growing up, I listened to songs where the guitar was just in support of that song,” he reasons. “If the song needs a two-bar break, and then you want to hear the next vocal section, that’s what it needs. If it sounds like it needs a longer guitar section, then that’s what it needs. There’s even a track called ‘Love Is Hard’ that doesn’t have any solo. It’s the first thing I’ve ever recorded in my life where I literally don’t play one instrument. Eren Cannata co-wrote it [with Shane McAnally and Justin Tranter], and I really loved the demo with him playing all the instruments. I loved it so much I just went with his acoustic guitar. I’m that much in service of the song.”
increased knowledge.
The original column—at least as original as I know it—was called “Ask Mikey" and was written by Mike Soldano of Soldano Custom Amplification. At some point, Mike became too busy to author the column, so the magazine needed to find a knowledgeable replacement in the tube-amp world. They wound up calling another one of the top boutique amp companies, Budda, and spoke with my partner Scot Sier. Since the questions were of a technical nature, Scot asked me if I would like to write the column. Upon accepting the challenge, the column in Musicians Hotline became Ask Budda. Once Hotline became Premier Guitar, the name of the column also changed to Ask Amp Man, and the tradition of answering readers' questions continued.
First, let me say that it's been an honor to have authored this column for so many years and to have been associated with Premier Guitar. The publication is well respected by its readers, as are the authors and columnists within. I know, because I'm told this all the time. I have been in the business of repairing and modifying, as well as designing and building, guitar amps for about 35 years now, and am probably as well known for writing this column as I am for the amp business.
The hands that have been inside of countless amps have also been on the necks of many, many guitars. Here, Jeff Bober lays into a favorite Strat. Photo by Robert Jordan
I was recently reminded of an instance when I was attending one of the big guitar manufacturers' “experience" parties. There was a gentleman performing onstage with the likes of Davy Knowles and David Grissom, and I really enjoyed his performance. (No disrespect to those other two players. Ha-ha!) I spoke to him after his set, later in the evening, and told him I really enjoyed his playing and his tone. At the time, I guess I looked similar to the frontman of a very successful band (dyed blond, coiffed hair with a bit of a beard and moustache), so he engaged in conversation with me. After a minute or two he noticed the name on my badge and said something to the effect of: “Man, I was just being nice to you because I thought you were Chad. You're the guy who writes the Ask Amp Man column! Now I'm really happy to meet you." That's not the first or the last time I've been acknowledged and thanked for being the author of this column—and I am very appreciative of that.
I've always looked at the column as a way to help people: be it someone who lives nowhere near anyone with the ability to diagnose or repair an amp, or someone with a desire to improve an amplifier and make it better suited to his or her needs. Although some have said it would be a great platform for self- or brand promotion, I never thought that appropriate for the column, so I tried never to use it in such a manner. It was always fun to read the questions and think about the possible causes of a problem or symptom, or a way I could help owners tweak or modify an amp to achieve a better result for them. It was also interesting to find someone whose need or application was outside the box, which prompts one to look at things with a different perspective. This is all part of the learning process, which makes everyone better at what they do. Of course, there are times where you just have to say, “No, you can't do that!" Ha-ha!
I also really enjoyed bringing you, as of late, interesting amps that have crossed my bench. For all the years I've been in this business, I still occasionally come across something I haven't seen before or seen only a few of because there simply aren't many of them around.
Putting his own amps, and a Gibson Les Paul, to use, Jeff rocks on the big stage with Johnny Chill, a side project of John Palumbo of Crack the Sky. Photo by Ellen Wiley
And then there are amps that were manufactured by relatively small companies—well known in their day, but after not being manufactured for decades and initially built in small numbers, they slowly fall off the radar. I have done columns on amps such as West and Sundown, where, after the columns were published, the likes of Dave West or Dennis Kager have contacted me and thanked me for writing a column on their amps. Something as simple as that brings one such joy, and for that I'm grateful.
I hope I've been able to bring at least a few of you a little bit of joy, or a sense of accomplishment—or, at the very least, increased knowledge. That said, there's only so much one can write in a column for more than 13 years without repeating one's self, so I've decided to bring it to an end. I'll still be designing, building, and repairing amps (which I really love to do), and if the folks at Premier Guitar are so inclined, maybe bringing you a feature story now and then. Or maybe something entirely different. Who knows! And if you'd like to hear what others in this wonderful world of music are up to, you know you can also hear me, as well as my co-host Mick Marcellino, on our weekly Amps & Axes podcast.
To bring this to a close, I'd like to leave you all with just a little bit of my philosophy: Live in the moment and be practical. We are all (at least most of us) guitarists. And that can come with the search for the ultimate tone, but don't let it get to the point of obsession. We live in an imperfect world—there is no perfection! If you keep lusting after every new guitar, amplifier, cable, capacitor, tube, speaker, pedal, pick, or battery, you will never be satisfied. If you have the opportunity to try or experience any or all of those … great. But it's not going to make or break you. Some of the best music in the world has been made on the most basic collection of materials, so do the best with what you have and improve or upgrade when it's practical. After all, music is supposed to be fun and good for the soul, so don't ruin that with obsessions. Life is too short. Take time to smell the roses. Or coffee. Coffee is good, too! Learn, have fun, respect other musicians, and, just as Frank Zappa said, “Play yer guitar!"
All the best, Jeff.
Except for the gain issue reader Rick Patterson describes, this month's amp is in remarkably good condition for
its half-century lifespan.
Dear Amp Man,
I have a '60s amp sold by Fender. It's a Regal R-1160 dual 6V6 with tremolo. Seems to be the same as a Lectrolab R600B. This amp does not saturate before almost full volume, and it's very subtle at that. I read your column on modifying negative feedback loops and I'm wondering if you could look at the schematic and show me where I would make this modification and what value caps you would recommend? I'm new to this sort of modification and would like to improve the tone without destroying the amp. If you need any pics, I can provide whatever you like.
All components and controls on this Regal R-1160 seem original, except this replacement speaker:
a Ted Weber Legacy Series.
Hi Rick,
Thanks for reading Ask Amp Man and thank you for your question. But even more, thank you for bringing this amp to my attention. I don't believe I was aware of Fender selling any amp that didn't have their name on it, but it does say right on the control panel “Distributed exclusively by Fender Sales Inc., Santa Ana, Calif.," so it's a very cool little piece of history, for sure. And to top it off, sans replacement speaker, it's in great shape!
Regarding your desire to modify the feedback loop in this amp to enable it to break up sooner: That's a good idea and a good place to start with many amps, but unfortunately not here. The first thing I noticed on the schematic you sent along with your question was that this amp doesn't even have a negative feedback loop! Not really unusual, but most amps without this tend to break up a bit more, so I was surprised that you say this does not.
to your expectations.
I would first suggest making sure the preamp tubes are not a contributing factor, and then possibly have a qualified tech give the amp a quick check to see if all seems well. Pay attention to the bypass capacitor across the output stage cathode resistor (Photo 1). While this doesn't control the amount of front-end gain in the amp, a bad or weak one can sure make an amp sound anemic.
If the tubes and bypass capacitor seem good but the amp doesn't have a lot of inherent gain, this could actually be an asset to some musicians. There are a couple of scenarios where lower gain is preferred—one being in a harp amp, but the other, more near and dear to guitar players, is if the amp is to be used as a pedal platform. In this case, the lower gain and higher headroom of an amp can really let the pedals shine. Some refer to such an amp as “pedal friendly."
Photo 1
That said, your desire is to get more crunch from this '60s jewel, so I do have a suggestion. Since both channels on this amp are virtually identical, why don't we leave channel 2 stock and modify channel 1 to bring it closer to your expectations? Sound good? Okay, let's go.
Photo 2
Hot modding. First, locate R7 in the amplifier (Photo 2). This is a cathode resistor for the first gain stage of channel 1. It is un-bypassed, so let's add a bypass cap across it to get more signal gain from this stage. I would use anything between a 4.7 µF to 10 µF, 25V DC. Plenty of amps use a 25 µF on up to a 250 µF cap, but anything that big may yield too much gain in the lower frequencies and that's something that would just muddy up the sound in a low-power, open-back amp such as this. Be sure to connect the positive side to the tube end of the resistor. If access to the resistor is too prohibited, connect the + side to pin 8 on the tube socket and connect the – side to the ground lug of the terminal strip.
Photo 3
Next, locate R15 (Photo 3). This will be one of the mixing resistors supplying the signal from channel 1. According to the schematic/parts list for your amp, this should be a 220k resistor. In your amp, however, both mixing resistors are 470k. This could also be a contributing factor in the lack of gain you say the amp has, but, regardless, let's leave channel 2 alone. I would suggest attaching a 220k resistor in parallel across the 470k resistor from channel 1. This will give you a stronger signal from channel 1.
There are a few other tricks that can be done, but some require the actual removal of components from the amp. The complete unsoldering and removal of components from tube sockets and terminal strips is often best left to someone with a considerable amount of experience in such matters. Other mods can require a bit of trial and error before a final component value decision is reached. I believe the modifications done above should give you an amp that you can push into overdrive much more easily, while leaving one channel cleaner for other uses. You could even get creative and use an A/B box to switch between the two channels for a lead/rhythm setup.
There you have it. I hope your Regal can now generate some royal sounds!
A rear view displays the EV 12L speaker and array of 6L6 power tubes and three 12AX7s. The reverb is solid-state, driven by a pair of discreet transistors.
Solid-state of the union. The first thing you notice when looking at the tube compliment is that the amp only has three preamp tubes. While this is certainly enough to achieve the typical amount of gain for the era, it’s not enough to support the onboard reverb. That’s because this amp is a hybrid: a mix of tube and solid-state circuitry. A pair of discrete transistors drive the reverb tank, which I think may be more reliable than driving the tank with IC chips, as is pretty typical today.
While all the overdrive in the amp is developed strictly with tubes, there are a few parts of the audio path that involve solid-state design. The first is the tone controls. Traditional tone controls can only attenuate (cut) their respective frequencies. The bass, middle, and treble controls in this Carvin amp are IC driven and are active controls, which means they can boost, as well as cut, frequencies.
Photo 1 — Amp Man suggests lifting one end of the wire coming from the push-pull pot on the master volume so the sound of the amp opens up—restoring its high frequencies.
Pretty cool, but setting them can be a bit more critical than your typical tube amp. The other part of the signal path that utilizes solid-state circuitry is, of course, the EQ, which also can be used to cut or boost frequencies. The EQ is assignable to either the rhythm or lead channel, but not both. This is not atypical, but if you think about it, it is a bit strange, as you cannot use the EQ to establish the signature tone of the amp. It can only be used for making substantial tonal changes to either channel, which can be nice—and, with the “M” amps of this era, necessary for the overdrive channel, in my opinion—but is not really necessary in this amp. Lastly, the presence control in this Carvin works in the feedback loop, as in most traditional tube amps, but is changed in the later X series amps to be included as part of the active tone controls. So far, this is a cool amp, but let’s get into it and make a few tweaks so it becomes even cooler and more usable.
Ins and outs. The first thing you hear about this amp is that it has its own sound. This is immediately noticeable in the rhythm channel. It has a very full bottom end and a nice top end, but doesn’t sound like a traditional F-style clean. That’s not to say it can’t, as that’s where the EQ can come in handy, and I think the clean sound is very unique and useable—especially with the bright function engaged. Now let’s switch over to the lead channel, as this is where the amp can stand some improvement. The lead mode master volume control is a push-pull pot and has two options: normal (in) and pull for “Hi Lead.” In Hi Lead mode, the drive channel is very useable and matches relatively well with the rhythm channel, but in the in-position normal mode, it is, in my opinion, unusable. It’s extremely dark and sounds like someone threw a few moving blankets over the amp. Here’s where we can do a few changes to make this amp sound better.
Photo 2 — Wanna match the tone on both channels? Our columnist suggests removing the 22 µF capacitor and replacing it with a 4.7k resistor with a 0.022 µF capacitor in parallel.
If we follow the schematic, or better and easier yet, the wires coming from the push-pull switch on the rear of the master volume pot, we see that they connect to two different capacitors. One shunts most of the high frequencies to ground. This one needs to go! Simply lift one end of the capacitor from the circuit board and you’re good to go (Photo 1). If you follow the other wire, you’ll see that it connects to a 22 µF capacitor whose other end is attached to pin 3 of V1. When this cap is connected via the switch to ground, it adds a considerable amount of gain to this stage—especially to the bottom end.
The problem is, there is so much gain that the bottom end starts to choke at higher gain settings, and it especially does so when the output power switch is set to 60 percent. To alleviate this, remove this cap and replace it with a 4.7k resistor with a 0.022 µF capacitor in parallel (Photo 2). Now, with the master volume on the lead channel pulled out in the Hi Lead mode, the tone of both channels matches very well. Pushing the Hi Lead pot in actually increases the gain in a very balanced way and gives the amp even more drive and sustain.
And there you have it: an amp whose boogie gives the competition a serious run for its money. Enjoy!