Dear Amp Man,
I am unable to find anything on cascading the half-unused tube in an AA371 Bassman. I have converted the amp to a Marshall tone stack and other suggestions you've made very successfully, but found nothing on tapping into the unused gain stage for the bass side. I've left the normal channel mostly stock and really want more gain on the modded side. The article you wrote on the Supro (“Modding a Supro 6420 Thunderbolt") got me inspired to try this. I've been looking for a layout over a schematic; I'd feel much safer with a layout so I don't damage anything. I'd love a little more gain and to make full use of that tube. Help or a link would be greatly appreciated.
Thanks,
Kevin
Hi Kevin,
It's nice to hear you've successfully incorporated some of my suggestions. Bassman amps have always been a great platform for mods—they're easy to work on and there are quite a few fun things you can do. Because I currently don't have a Bassman to mod and then photograph, I've tried to do the next best thing and draw the modification layout and connections directly on the Fender factory drawing of the physical layout. I'll also give you a list of necessary parts and a step-by-step procedure. Let's go!
This illustration shows the gain stage mod, breaking out the area around tube positions V1 and V2 from a schematic drawing of an AA371 Bassman amp.
This mod is not very extensive, and you'll only need a few parts and a couple of pieces of wire:
- one 3-lug terminal strip (the kind typically manufactured by Keystone)
- two 470k resistors (1/2 watt is sufficient, but I typically use 1 watt for almost everything)
- one 100k resistor
- one 2.7k resistor
- one 0.022 µF 600V capacitor (poly or foil)
- one 0.68 µF 25V or greater capacitor
- two small pieces of shrink tubing or electrical tape
- one ¼" 4-40 screw and nut
- less than a foot of 20- or 22-gauge wire
Before beginning, be sure the filter caps are discharged. If you don't know how to do this, find someone who does. Then:
1. Install the terminal strip in a comfortable location between tube positions V1 and V2. You'll need to drill a small hole in the chassis and mount it using the 4-40 screw and nut. Be sure the screw and nut are very tight. This point will act as a ground connection.
2. Unsolder the wire coming from the bass channel input jacks (red, according to the schematic) that is connected to pin 2 of V1. Connect an additional piece of wire to this and insulate the connection with a piece of shrink tubing or tape. Cut to length and connect the other end to pin 2 of V2 (the input to the unused half of V2).
3. Connect one end of the 100k resistor to pin 1 of V2, but do not solder yet. Connect the other end to the eyelet where the two 100k V1 plate resistors are connected. You may need an additional piece of wire to connect to the resistor, so solder and insulate as necessary.
Warning:
All tube amplifiers contain lethal voltages. The most dangerous voltages are stored in electrolytic capacitors, even after the amp has been unplugged from the wall. Before you touch anything inside the amp chassis, it's imperative that these capacitors are discharged. If you are unsure of this procedure, consult your local amp tech.
4. Connect the 0.022 µF capacitor to pin 1 of V2. You may now solder the connection. Connect the other end of the capacitor to the top terminal strip in the drawing. Do not solder this end yet.
5. Connect one end of the 2.7k resistor and the 0.68 µF capacitor to terminal 3 of V2. Connect the other end of the resistor and capacitor to the center terminal of the terminal strip. You can now solder pin 3 of V2.
6. Connect one end of a 470k resistor to the bottom terminal and the other end to the center terminal of the terminal strip. You may now solder the center terminal.
7. Connect one end of the other 470k resistor to the bottom terminal and the other end to the top terminal. You may now solder the top terminal.
8. Connect another short wire to the bottom terminal of the terminal strip. Cut to length and connect the other end to pin 2 of V1. You may now solder both connections.
And that's it. This modification is based on the typical front end of a Marshall 2204-style head and approximates its gain control set to about 60 percent. The gain can be increased or decreased depending on the relative values of the 470k resistors. If you'd like to make the gain easily variable, you can replace the two 470k resistors with a 1 mA pot. Simply remove the 470k resistors, connect the CW terminal of the pot to the top terminal on the strip, the CCW terminal to the center ground terminal, and the wiper to the bottom terminal. This is now your front-end gain control. If you need more top end, simply connect a small value cap (start with a 100 pF ceramic cap) between the CW and wiper terminal. As with most tube amp modifications like this, feel free to experiment with slightly larger or smaller resistor or capacitor values for your own custom version.
Now break out some humbuckers and a 4x12, and rock on!
[Updated 8/17/21]
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Duane Denison of the Jesus Lizard, EGC Chessie in hands, coaxing some nasty tones from his Hiwatt.
The Jesus Lizard’s sixth album, Blue, served as the band’s final statement from the frontlines of noisy rock for the next 26 years. By the time of their dissolution in 1999, they’d earned a reputation for extreme performances chock full of hard-hitting, machine-like grooves delivered by bassist David Wm. Sims and, at their conclusion, drummer Mac McNeilly, at times aided and at other times punctured by the frontline of guitarist Duane Denison’s incisive, dissonant riffing, and presided over by the cantankerous howl of vocalist David Yow. In the years since, performative, thrilling bands such as Pissed Jeans, METZ, and Idles have built upon the Lizard’s musical foundation.
Denison has kept himself plenty busy over the last couple decades, forming the avant-rock supergroup Tomahawk—with vocalist Mike Patton, bassist Trevor Dunn (both from Mr. Bungle), and drummer John Stanier of Helmet—and alongside various other projects including Th’ Legendary Shack Shakers and Hank Williams III. The Jesus Lizard eventually reunited, but until now have only celebrated their catalog, never releasing new jams.
The Jesus Lizard, from left: bassist David Wm. Sims, singer David Yow, drummer Mac McNeilly, and guitarist Duane Denison.
Photo by Joshua Black Wilkins
Back in 2018, Denison, hanging in a hotel room with Yow, played a riff on his unplugged electric guitar that caught the singer’s ear. That song, called “West Side,” will remain unreleased for now, but Denison explains: “He said, ‘Wow, that’s really good. What is that?’ And I said, ‘It’s just some new thing. Why don’t we do an album?’” From those unassuming beginnings, the Jesus Lizard’s creative juices started flowing.
So, how does a band—especially one who so indelibly captured the ineffable energy of live rock performance—prepare to get a new record together 26 years after their last? Back in their earlier days, the members all lived together in a band house, collectively tending to the creative fire when inspiration struck. All these years later, they reside in different cities, so their process requires sending files back and forth and only meeting up for occasional demo sessions over the course of “three or four years.”
“When the time comes to get more in performance mode, I have a practice space. I go there by myself and crank it up. I turn that amp up and turn the metronome up and play loud.” —Duane Denison
the Jesus Lizard "Alexis Feels Sick"
Distance creates an obstacle to striking while the proverbial iron is hot, but Denison has a method to keep things energized: “Practice loud.” The guitarist professes the importance of practice, in general, and especially with a metronome. “We keep very detailed records of what the beats per minute of these songs are,” he explains. “To me, the way to do it is to run it to a Bluetooth speaker and crank it, and then crank your amp. I play a little at home, but when the time comes to get more in performance mode, I have a practice space. I go there by myself and crank it up. I turn that amp up and turn the metronome up and play loud.”
It’s a proven solution. On Rack—recorded at Patrick Carney’s Audio Eagle studio with producer Paul Allen—the band sound as vigorous as ever, proving they’ve not only remained in step with their younger selves, but they may have surpassed it with faders cranked. “Duane’s approach, both as a guitarist and writer, has an angular and menacing fingerprint that is his own unique style,” explains Allen. “The conviction in his playing that he is known for from his recordings in the ’80s and ’90s is still 100-percent intact and still driving full throttle today.”
“I try to be really, really precise,” he says. “I think we all do when it comes to the basic tracks, especially the rhythm parts. The band has always been this machine-like thing.” Together, they build a tension with Yow’s careening voice. “The vocals tend to be all over the place—in and out of tune, in and out of time,” he points out. “You’ve got this very free thing moving around in the foreground, and then you’ve got this very precise, detailed band playing behind it. That’s why it works.”
Before Rack, the Jesus Lizard hadn’t released a new record since 1998’s Blue.
Denison’s guitar also serves as the foreground foil to Yow’s unhinged raving, as on “Alexis Feels Sick,” where they form a demented harmony, or on the midnight creep of “What If,” where his vibrato-laden melodies bolster the singer’s unsettled, maniacal display. As precise as his riffs might be, his playing doesn’t stay strictly on the grid. On the slow, skulking “Armistice Day,” his percussive chording goes off the rails, giving way to a solo that slices that groove like a chef’s knife through warm butter as he reorganizes rock ’n’ roll histrionics into his own cut-up vocabulary.
“During recording sessions, his first solo takes are usually what we decide to keep,” explains Allen. “Listen to Duane’s guitar solos on Jack White’s ‘Morning, Noon, and Night,’ Tomahawk’s ‘Fatback,’ and ‘Grind’ off Rack. There’s a common ‘contained chaos’ thread among them that sounds like a harmonic Rubik’s cube that could only be solved by Duane.”
“Duane’s approach, both as a guitarist and writer, has an angular and menacing fingerprint that is his own unique style.” —Rack producer Paul Allen
To encapsulate just the right amount of intensity, “I don’t over practice everything,” the guitarist says. Instead, once he’s created a part, “I set it aside and don’t wear it out.” On Rack, it’s obvious not a single kilowatt of musical energy was lost in the rehearsal process.
Denison issues his noisy masterclass with assertive, overdriven tones supporting his dissonant voicings like barbed wire on top of an electric fence. The occasional application of slapback delay adds a threatening aura to his exacting riffage. His tones were just as carefully crafted as the parts he plays, and he relied mostly on his signature Electrical Guitar Company Chessie for the sessions, though a Fender Uptown Strat also appears, as well as a Taylor T5Z, which he chose for its “cleaner, hyper-articulated sound” on “Swan the Dog.” Though he’s been spotted at recent Jesus Lizard shows with a brand-new Powers Electric—he points out he played a demo model and says, “I just couldn’t let go of it,” so he ordered his own—that wasn’t until tracking was complete.
Duane Denison's Gear
Denison wields his Powers Electric at the Blue Room in Nashville last June.
Photo by Doug Coombe
Guitars
- Electrical Guitar Company Chessie
- Fender Uptown Strat
- Taylor T5Z
- Gibson ES-135
- Powers Electric
Amps
- Hiwatt Little J
- Hiwatt 2x12 cab with Fane F75 speakers
- Fender Super-Sonic combo
- Early ’60s Fender Bassman
- Marshall 1987X Plexi Reissue
- Victory Super Sheriff head
- Blackstar HT Stage 60—2 combos in stereo with Celestion Neo Creamback speakers and Mullard tubes
Effects
- Line 6 Helix
- Mantic Flex Pro
- TC Electronic G-Force
- Menatone Red Snapper
Strings and Picks
- Stringjoy Orbiters .0105 and .011 sets
- Dunlop celluloid white medium
- Sun Studios yellow picks
He ran through various amps—Marshalls, a Fender Bassman, two Fender Super-Sonic combos, and a Hiwatt Little J—at Audio Eagle. Live, if he’s not on backline gear, you’ll catch him mostly using 60-watt Blackstar HT Stage 60s loaded with Celestion Neo Creambacks. And while some boxes were stomped, he got most of his effects from a Line 6 Helix. “All of those sounds [in the Helix] are modeled on analog sounds, and you can tweak them endlessly,” he explains. “It’s just so practical and easy.”
The tools have only changed slightly since the band’s earlier days, when he favored Travis Beans and Hiwatts. Though he’s started to prefer higher gain sounds, Allen points out that “his guitar sound has always had teeth with a slightly bright sheen, and still does.”
“Honestly, I don’t think my tone has changed much over the past 30-something years,” Denison says. “I tend to favor a brighter, sharper sound with articulation. Someone sent me a video I had never seen of myself playing in the ’80s. I had a band called Cargo Cult in Austin, Texas. What struck me about it is it didn’t sound terribly different than what I sound like right now as far as the guitar sound and the approach. I don’t know what that tells you—I’m consistent?”
YouTube It
The Jesus Lizard take off at Nashville’s Blue Room this past June with “Hide & Seek” from Rack.
Keith Urban has spent decades traveling the world and topping global country-music charts, and on this episode of Wong Notes, the country-guitar hero tells host Cory Wong how he conquered the world—and what keeps him chasing new sounds on his 6-string via a new record, High, which releases on September 20.
Urban came up as guitarist and singer at the same time, and he details how his playing and singing have always worked as a duet in service of the song: “When I stop singing, [my guitar] wants to say something, and he says it in a different way.” Those traits served him well when he made his move into the American music industry, a story that begins in part with a fateful meeting with a 6-string banjo in a Nashville music store in 1995.
It’s a different world for working musicians now, and Urban weighs in on the state of radio, social media, and podcasts for modern guitarists, but he still believes in word-of-mouth over the algorithm when it comes to discovering exciting new players.
And in case you didn’t know, Keith Urban is a total gearhead. He shares his essential budget stomps and admits he’s a pedal hound, chasing new sounds week in and week out, but what role does new gear play in his routine? Urban puts it simply: “I’m not chasing tone, I’m pursuing inspiration.”
