At a seemingly modest 30 watts, this Marshall JTM 45 Plexi reissue can still peel the paint off the walls of small rooms. But the pentode/triode mod rectifies that.
Hello avid Ask Amp Man readers. This month, instead of selecting a question that one of you sent in, I've decided to answer a question I hear quite often: How can I use one amp for all playing situations?
Because we live in a musical environment where sound systems are bigger and/or venues are smaller, the days of needing your 50- or 100-watt amp for every gig are fewer. But some players still prefer to carry one amp for all occasions: So what is one to do?
There is the possibility of having a power-scaling circuit installed in your favorite amp, but that is a somewhat involved installation and, for some, the result may not be their cup of tea. Another option is to remove two of the four output tubes in your amp.
This, however, theoretically changes the output impedance by 50 percent, and in the case of most Fender amps, there's no option to select a different output impedance, so you're stuck with a mismatch. Plus, this option only works with amplifiers that have four output tubes, so what do you do if you have an amplifier with only two output tubes?
Well, you could install a pentode/triode switch. This will work with amplifiers that have two or four output tubes and will reduce the power by approximately 40 percent or more. When the switch is in full power, or pentode, mode, the amp is completely stock. When it is in half-power, or triode, mode, the output tubes are wired to run in a configuration that results in a reduction of power. This mod can be done in most any Fender or Marshall type amp, or any amp which utilizes a pentode-style output tube, such as a 6L6, EL34, 6V6, 6550, KT66, KT88, etc. This is actually the same circuit you will find in the Marshall 2550 and 2555 Silver Jubilee amps labeled as high and low power. The example here is a Marshall JTM45 Plexi reissue.
This rotary half-power switch was installed in an output jack space for minimal invasiveness and easy access,
and can be easily undone.
The first thing you'll need to do is install a DPDT (double pole/double throw) switch in the amp. This can be a toggle or rotary switch. Since this amp would probably not be used with more than one cabinet, I chose to install a rotary version in place of one of the speaker output jacks on the rear panel. No extra holes and completely reversible. One set of contacts (or pole) of the DPDT switch will be used for one side of the push-pull output stage and the other pole for the other side. The common terminal of each side will connect to the tube screen grid pin.
In the case of a typical octal tube, this will be pin 4 and will usually have a 470 ohm or 1K ohm resistor attached. Leave the resistor attached to the tube socket and disconnect whatever is connected to the other side of the resistor. This will typically be a wire coming from the B+b section of the power supply. We will be connecting this to the switch. In many amps, these screen grid resistors may be tied together with a wire or solid buss wire. In a two-output tube amp, disconnect the wire connecting the resistors. In a four-output tube amp, leave the right pair connected to each other and the left pair connected to each other and disconnect the wire in the center connecting the right pair to the left pair. Now we should be ready to wire the switch.
Fig. 1
First, connect a wire to the common terminal of one side (or pole) of the switch. Connect the other end to the screen grid resistor(s) of the right tube(s) (Fig 1). Next, connect a wire to one of the switched terminals on that same pole of the switch. Connect the other end to that same tube's plate connection (Fig 2).
Fig. 2
On a typical octal tube, this will be pin 3. In a four-tube amp, pin 3 on both tubes will be connected with a wire. Attaching your wire to either pin 3 will be fine. Next, do the same for the other pole of the switch (Fig 3)—common to screen grid resistor(s) of the other tube(s) and the switched terminal (same position as the other side) to pin 3 of the other tube(s).
Fig. 3
This should now leave us with just two open terminals on the switch. These should both be on the same end of the switch. Connect both of these terminals together and attach them to the B+b wire that you disconnected from the screen grid resistors (Fig 4). You may need to use an extra length of wire to reach the original B+b wire, but that's okay. Just make sure the splice is insulated well.
Fig. 4
There you have it. In one switch position, the amp will be completely stock (full power pentode mode), and in the other, the output should be reduced (half-power triode mode).
Now go rock out … but more quietly.
A mix of futuristic concepts and DeArmond single-coil pickups, the Musicraft Messenger’s neck was tuned to resonate at 440 Hz.
Until its untimely end, Musicraft made roughly 250 Messengers in various configurations: the mono-output Messenger and the flagship Messenger Stereophonic, both of which could come with the “Tone Messer” upgrade, a built-in distortion/fuzz circuit. The company’s first catalog also featured a Messenger Bass, a wireless transmitter/receiver, and various models of its Messenger Envoy amplifier, very few of which have survived, if many were ever made at all.
“To this day, even fans will sometimes call the decision to use DeArmonds the Messenger’s ‘Achilles’ heel.’”
Upon its release, the Messenger was a mix of futuristic concepts and DeArmond single-coil pickups that were more likely to be found on budget instruments than pricier guitars such as these. The Messengers often featured soapbar-style DeArmonds, though some sported a diamond grille. (To this day, even fans will sometimes call the decision to use DeArmonds the Messenger’s “Achilles’ heel.”) The Stereophonic model, like the one featured in this edition of Vintage Vault, could be plugged into a single amplifier as normal, or you could split the bridge and neck pickup outputs to two separate amps.
One of the beloved hallmarks of the guitars are their magnesium-aluminum alloy necks, which continue as a center block straight through the tailpiece, making the guitars relatively lightweight and virtually immune to neck warping, while enhancing their playability. Thanks to the strength of that metal-neck design, there’s no need for a thick heel where it meets the body, granting unprecedented access to the higher end of the fretboard.
This Stereophonic model could be plugged into a single amplifier as normal, or you could split the bridge and neck pickup outputs to two separate amps.
The neck was apparently also tuned to have a resonant frequency of 440 Hz, which, in all honesty, may be some of that 1967 “whoa, man” marketing continuing on through our modern-day guitar discourse, where this fact is still widely repeated on forums and in YouTube videos. (As one guitar aficionado to the next, what does this even mean in practice? Would an inaudible vibration at that frequency have any effect at all on the tone of the guitar?)
In any event, the combination of that metal center block—resonant frequency or not—the apple-shaped hollow wooden body of the guitar, and the cat’s-eye-style “f-holes” did make it prone to gnarly fits of feedback, especially if you engaged the Tone Messer fuzz and blasted it all through the high-gain amp stacks favored by the era’s hard rockers.
The most famous devotee of the Messenger was Grand Funk Railroad’s Mark Farner, who used the guitar—and its Tone Messer circuitry—extensively on the group’s string of best-selling records and in their defining live shows, like the Atlanta Pop Festival 1970 and their sold-out run at New York’s Shea Stadium in 1971. But even Farner had some misgivings.
The Messengers often featured soapbar-style DeArmonds, though some sported a diamond grille.
In a 2009 interview, he talked about his first test-run of the guitar: “After I stuffed it full of foam and put masking tape over the f-holes to stop that squeal, I said, ‘I like it.’” He bought it for $200, on a $25-per-pop installment plan, a steal even at the time. (He also made it over with a psychedelic paint job, befitting the era, and experimented with different pickups over the years.)
When these guitars were new in 1967, the Messenger Stereophonic in morning sunburst, midnight sunburst, or mojo red would have run you $340. By 1968, new stereo models started at $469.50. Recent years have seen prices for vintage models steadily increase, as the joy of this rarity continues to thrill players and collectors. Ten years ago, you could still get them for about $1,500, but now prices range from $3,000 to $6,000, depending on condition.
Our Vintage Vault pick today is listed on Reverb by Chicago’s own SS Vintage. Given that it’s the stereo model, in very good condition, and includes the Tone Messer upgrade, its asking price of $5,495 is near the top-end for these guitars today, but within the usual range. To those readers who appreciate the vintage vibe but don’t want the vintage price tag, Eastwood Guitars offers modern reissues, and eagle-eyed buyers can also find some very rare but less expensive vintage MIJ clones made in the late ’60s and early ’70s.
Sources: Reverb listing from SS Vintage, Reverb Price Guide sales data, Musicraft July 1, 1967 Price Schedule, 1968 Musicraft Catalog, Chicago Music Exchange’s “Uncovering The Secret Sounds of the 1967 Musicraft Messenger Guitar,” MusicPickups.com article on the Messenger.Submarine Pickups boss Pete Roe at his workstation.
Still, we think we know what pickups should sound and look like. Lucky for us, there have always been plenty of pickup builders who aren’t so convinced. These are the makers who devised the ceramic-magnet pickup, gold-foils, and active, high-gain pickups. In 2025, nearly 100 years after the first pickup bestowed upon a humble lap-steel guitar the power to blast our ears with soundwaves, there’s no shortage of free-thinking, independent wire-winders coming up with new ways to translate vibrating steel strings into thrilling music.
Joe Naylor, Chris Mills, and Pete Roe are three of them. As the creative mind behind Reverend Guitars, Naylor developed the Railhammer pickup, which combines both rail and pole-piece design. Mills, in Pennsylvania, builds his own ZUZU guitars with wildly shaped, custom-designed pickups. And in the U.K., Roe developed his own line of hexaphonic pickups to achieve the ultimate in string separation and note definition. All three of them told us how they created their novel noisemakers.
Joe Naylor - Railhammer Pickups
Joe Naylor, pictured here, started designing Railhammers out of personal necessity: He needed a pickup that could handle both pristine cleans and crushing distortion back to back.
Like virtually all guitar players, Joe Naylor was on a personal tone quest. Based in Troy, Michigan, Naylor helped launch Reverend Guitars in 1996, and in the late ’90s, he was writing and playing music that involved both clean and distorted movements in one song. He liked his neck pickup for the clean parts, but it was too muddy for high-gain playing. He didn’t want to switch pickups, which would change the sound altogether.
He set out to design a neck pickup that could represent both ends of the spectrum with even fidelity. That led him to a unique design concept: a thin, steel rail under the three thicker, low-end strings, and three traditional pole pieces for the higher strings, both working with a bar magnet underneath. At just about a millimeter thick, rails, Naylor explains, only interact with a narrow section of the thicker strings, eliminating excess low-end information. Pole pieces, at about six millimeters in diameter, pick up a much wider and less focused window of the higher strings, which works to keep them fat and full. “If you go back and look at some of the early rail pickups—Bill Lawrence’s and things like that—the low end is very tight,” says Naylor. “It’s almost like your tone is being EQ’d perfectly, but it’s being done by the pickup itself.”
That idea formed the basis for Railhammer Pickups, which began official operations in 2012. Naylor built the first prototype in his basement, and it sounded great from the start, so he expanded the format to a bridge pickup. That worked out, too. “I decided, ‘Maybe I’m onto something here,’” says Naylor. Despite the additional engineering, Railhammers have remained passive pickups, with fairly conventional magnets—including alnico 5s and ceramics—wires, and structures. Naylor says this combines the clarity of active pickups with the “thick, organic tone” of passive pickups.
“It’s almost like your tone is being EQ’d perfectly, but it’s being done by the pickup itself.” —Joe Naylor
The biggest difficulty Naylor faced was in the physical construction of the pickups. He designed and ordered custom molds for the pickup’s bobbins, which cost a good chunk of money. But once those were in hand, the Railhammers didn’t need much fiddling. Despite their size differences, the rail and pole pieces produce level volume outputs for balanced response across all six strings.
Naylor’s formula has built a significant following among heavy-music players. Smashing Pumpkins’ Billy Corgan is a Railhammer player with several signature models; ditto Reeves Gabrels, the Cure guitarist and David Bowie collaborator. Bob Balch from Fu Manchu and Kyle Shutt from the Sword have signatures, too, and other players include Code Orange’s Reba Meyers, Gogol Bordello’s Boris Pelekh, and Voivod’s Dan “Chewy” Mongrain.
Chris Mills - ZUZU Pickups
When Chris Mills started building his own electric guitars, he decided to build his own components for them, too. He suspected that in the course of the market’s natural thinning of the product herd, plenty of exciting options had been left unrealized. He started working with non-traditional components and winding in non-traditional ways, which turned him on to the idea that things could be done differently. “I learned early on that there are all kinds of sonic worlds out there to be discovered,” says Mills.
Eventually, he zeroed in on the particular sound of a 5-way-switch Stratocaster in positions two and four: Something glassy and clear, but fatter and more dimensional. In Mills’ practice, “dimensional” refers to the varying and sometimes simultaneous sound qualities attained from, say, a finger pad versus a fingernail. “I didn’t want just one thing,” says Mills. “I wanted multiple things happening at once.”
Mills wanted something that split the difference between a humbucker’s fullness and the Strat’s plucky verve, all in clean contexts. But he didn’t want an active pickup; he wanted a passive, drop-in solution to maximize appeal. To achieve the end tone, Mills wired his bobbins in parallel to create “interposed signal processing,” a key piece of his patented design. “I found that when I [signal processed] both of them, I got too much of one particular quality, and I wanted that dimensionality that comes with two qualities simultaneously, so that was essential,” explains Mills.
Mills loved the sound of alnico 5 blade magnets, so he worked with a 3D modeling engineer to design plastic bobbins that could accommodate both the blades and the number of turns of wire he desired. This got granular—a millimeter taller, a millimeter wider—until they came out exactly right. Then came the struggle of fitting them into a humbucker cover. Some key advice from experts helped Mills save on space to make the squeeze happen.
Mills’ ZUZUbuckers don’t have the traditional pole pieces and screws of most humbuckers, so he uses the screw holes on the cover as “portholes” looking in on a luxe abalone design. And his patented “curved-coil” pickups feature a unique winding method to mix up the tonal profile while maintaining presence across all frequencies.
“I learned early on that there are all kinds of sonic worlds out there to be discovered.” —Chris Mills
Mills has also patented a single-coil pickup with a curved coil, which he developed to get a different tonal quality by changing the relative location of the poles to one another and to the bridge. Within that design is another patented design feature: reducing the number of turns at the bass end of the coil. “Pretty much every pickup maker suggests that you lower the bass end [of the pickup] to compensate for the fact that it's louder than the treble end,” says Mills. “That'll work, but doing so alters the quality and clarity of the bass end. My innovation enables you to keep the bass end up high toward the strings.”
Even Mills’ drop-in pickups tend to look fairly distinct, but his more custom designs, like his curved-coil pickup, are downright baroque. Because his designs don’t rely on typical pickup construction, there aren’t the usual visual cues, like screws popping out of a humbucker cover, or pole pieces on a single-coil pickup. (Mills does preserve a whiff of these ideals with “portholes” on his pickup covers that reveal that pickup below.) Currently, he’s excited by the abalone-shell finish inserts he’s loading on top of his ZUZUbuckers, which peek through the aforementioned portholes.
“It all comes down to the challenge that we face in this industry of having something that’s original and distinctive, and also knowing that with every choice you make, you risk alienating those who prefer a more traditional and familiar look,” says Mills.
Pete Roe - Submarine Pickups
Roe’s stick-on Submarine pickups give individual strings their own miniature pickup, each with discrete, siloed signals that can be manipulated on their own. Ever wanted to have a fuzz only on the treble strings, or an echo applied just to the low-register strings? Submarine can achieve that.
Pete Roe says that at the start, his limited amount of knowledge about guitar pickups was a kind of superpower. If he had known how hard it would be to get to where he is now, he likely wouldn’t have started. He also would’ve worked in a totally different way. But hindsight is 20/20.
Roe was working in singer-songwriter territory and looking to add some bass to his sound. He didn’t want to go down the looping path, so he stuck with octave pedals, but even these weren’t satisfactory for him. He started winding his own basic pickups, using drills, spools of wire, and magnets he’d bought off the internet. Like most other builders, he wanted to make passive pickups—he played lots of acoustic guitar, and his experiences trying to find last-minute replacement batteries for most acoustic pickups left him scarred.
Roe started building a multiphonic pickup: a unit with multiple discrete “pickups” within one housing. In traditional pickups, the vibration from the strings is converted into a voltage in the 6-string-wide coils of wire within the pickup. In multiphonic pickups, there are individual coils beneath each string. That means they’re quite tiny—Roe likens each coil to the size of a Tylenol pill. “Because you’re making stuff small, it actually works better because it’s not picking up signals from adjacent strings,” says Roe. “If you’ve got it set up correctly, there’s very, very little crosstalk.”
With his Submarine Pickups, Roe began by creating the flagship Submarine: a quick-stick pickup designed to isolate and enhance the signals of two strings. The SubPro and SubSix expanded the concept to true hexaphonic capability. Each string has a designated coil, which on the SubPro combine into four separate switchable outputs; the SubSix counts six outputs. The pickups use two mini output jacks, with triple-band male connectors to carry three signals each. Explains Roe: “If you had a two-channel output setup, you could have E, A, and D strings going to one side, and G, B, and E to the other. Or you could have E and A going to one, the middle two strings muted, and the B and E going to a different channel.” Each output has a 3-position switch, which toggles between one of two channels, or mute.
“I’m just saying there’s some unexplored territory at the beginning of the signal chain. If you start looking inside your guitar, then it opens up a world of opportunities.” —Pete Roe
This all might seem a little overly complicated, but Roe sees it as a simplification. He says when most people think about their sound, they see its origin in the guitar as fixed, only manipulatable later in the chain via pedals, amp settings, or speaker decisions. “I’m not saying that’s wrong,” says Roe. “I’m just saying there’s some unexplored territory at the beginning of the signal chain. If you start looking inside your guitar, then it opens up a world of opportunities which may or may not be useful to you. Our customers tend to be the ones who are curious and looking for something new that they can’t achieve in a different way.
“If each string has its own channel, you can start to get some really surprising effects by using those six channels as a group,” continues Roe. “You could pan the strings across the stereo field, which as an effect is really powerful. You suddenly have this really wide, panoramic guitar sound. But then when you start applying familiar effects to the strings in isolation, you can end up with some really surprising textural sounds that you just can’t achieve in any other way. You can get some very different sounds if you’re applying these distortions to strings in isolation. You can get that kind of lead guitar sound that sort of cuts through everything, this really pure, monophonic sound. That sounds very different because what you don’t get is this thing called intermodulation distortion, which is the muddiness, essentially, that you get from playing chords that are more complex than roots and fifths with a load of distortion.” And despite the powerful hardware, the pickups don’t require any soldering or labor. Using a “nanosuction” technology similar to what geckos possess, the pickups simply adhere to the guitar’s body. Submarine’s manuals provide clear instruction on how to rig up the pickups.
“An analogy I like to use is: Say you’re remixing a track,” explains Roe. “If you get the stems, you can actually do a much better job, because you can dig inside and see how the thing is put together. Essentially, Submarine is doing that to guitars. It’s allowing guitarists and producers to look inside the instrument and rebuild it from its constituent parts in new and exciting ways.”
In continued support of their 3x GRAMMY-nominated album Dark Matter, Pearl Jam will be touring select U.S. cities in April and May 2025.
Pearl Jam’s live dates will start in Hollywood, FL on April 24 and 26 and wrap with performances in Pittsburgh, PA on May 16 and 18. Full tour dates are listed below.
Support acts for these dates will be announced in the coming weeks.
Tickets for these concerts will be available two ways:
- A Ten Club members-only presale for all dates begins today. Only paid Ten Club members active as of 11:59 PM PT on December 4, 2024 are eligible to participate in this presale. More info at pearljam.com.
- Public tickets will be available through an Artist Presale hosted by Ticketmaster. Fans can sign up for presale access for up to five concert dates now through Tuesday, December 10 at 10 AM PT. The presale starts Friday, December 13 at 10 AM local time.
earl Jam strives to protect access to fairly priced tickets by providing the majority of tickets to Ten Club members, making tickets non-transferable as permitted, and selling approximately 10% of tickets through PJ Premium to offset increased costs. Pearl Jam continues to use all-in pricing and the ticket price shown includes service fees. Any applicable taxes will be added at checkout.
For fans unable to use their purchased tickets, Pearl Jam and Ticketmaster will offer a Fan-to-Fan Face Value Ticket Exchange for every city, starting at a later date. To sell tickets through this exchange, you must have a valid bank account or debit card in the United States. Tickets listed above face value on secondary marketplaces will be canceled. To help protect the Exchange, Pearl Jam has also chosen to make tickets for this tour mobile only and restricted from transfer. For more information about the policy issues in ticketing, visit fairticketing.com.
For more information, please visit pearljam.com.