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| Hey Jeff, I have a ‘66 Bassman head and I’d like to modify the Bass channel for smooth overdrive tones. The Normal channel is what I gig with, going from a Strat or Tele to my effects then to the Bassman, but I’d like to explore some natural amp overdrive and keep the Normal channel set for maximum clean headroom. I’ve seen some so-called Dumble schematics on the internet, but I don’t really want to turn the whole head into a Dumble clone; I just want to incorporate a few modifications to get a nice, smooth overdrive. Can you help me accomplish this? Thanks for your consideration, - Todd Lynch |
Hi Todd,
Not only do you have one of the nicest amps around for straight-ahead rock n’ roll guitar tones, but the chassis also holds a secret weapon for generating some great overdrive tones. The tone that comes from the Normal channel of a Bassman head connected to a 4x12 cabinet is classic rock in its purest form, but you should definitely be able to kick the Bass channel up a notch. The reason? The amp already has an extra stage of gain that is unused – there is one half of a 12AX7 preamp tube sitting there, waiting for our bidding.
While I’m not going to provide you with the exact schematic of the proposed modification, I will try to give you enough information to take to an experienced tech so they will be able to modify the amp for your desired results. In order to do this, they will need a copy of the Bassman’s schematic, along with a copy of the schematic for a standard Marshall 2203 or 2204 preamp. If dealing with an experienced tech, odds are they will already have these in their schematic collection. For the sake of simplification, I’ll refer to the Marshall schematic as “the schematic.”
First, the number two input jack on the Bass channel should be removed and replaced with a 1M-A pot. This will be used as your preamp volume control. Next, have him wire the output of the first gain stage to the aforementioned preamp volume control using the appropriate coupling caps and resistors shown in the schematic. Disregard the “low” input jack on the schematic as it is just used in this instance as a signal pass thru. From there, the signal should be sent to the input of the unused half of the available 12AX7 and the appropriate components installed to replicate the second gain stage of the schematic. The output of this stage would then go back over to the second half of the initial 12AX7, utilizing the appropriate circuitry per the schematic. The output of that second half should then be connected to the tone controls and original Volume control, which will now act as your Master Volume. Just to clarify things, the last part of the schematic will be different at this point. Since there is no fourth preamp section available in the Fender chassis, the tone stack we will end up with is plate-driven, as opposed to a cathode-driven stack. Other than that, you pretty much have a Bassman with the front end of a 2203 Master Volume Marshall in place of the Bass channel.
I’d like to add a few suggestions for your tech. Remember to change the value of the caps in the tone stack from 0.1uf to 0.022uf and remove the unused deep cap. If you want to get creative, since there’s no midrange control, you can use the deep switch to parallel a resistor across the existing midrange resistor, thereby converting the deep switch to a mid shift switch. Feel free to experiment with the values of the resistors, allowing you to adjust the midrange to taste. You can also change the bass pot from a 250K to a 1M for more bass range.
Want to really go over the top? Instead of using it as a mid-shift switch, repurpose the deep switch, using it to lift one end of the midrange resistor. It will now be a tone defeat switch – once engaged, the tone stack is defeated and the gain increases dramatically. I would leave off the .001 cap across the preamp volume control; I find it to be too brittle at lower settings. If the modified channel is still too bright, remove the 470pf cap that parallels the 470K resistor prior to the preamp volume control. If the channel is too woofy at higher gain settings, change the value of the first cathode bypass cap from 25uf to something substantially smaller, possibly a 0.68 or 1.0uf.
One last suggestion would be to consider using shielded cable on the long signal runs that go to and from the additional tube and preamp circuitry to help eliminate the possibility of any internal feedback or oscillation. Shielding the signal from the input jack isn’t a bad idea either.
There you have it. With a little personal tweaking by both you and your tech, you should be able to get a plethora of tones from your new MarshMan.
Jeff Bober
Co-Founder and Senior Design Engineer – Budda Amplification
jeffb@budda.com
www.budda.com
©2007 Jeff Bober
LR Baggs HiFi Duet High-fidelity Pickup and Microphone Mixing System
"When a guitar is “the one,” you know it. It feels right in your hands and delivers the sounds you hear in your head. It becomes your faithful companion, musical soulmate, and muse. It helps you express your artistic vision. We designed the Les Paul Studio to be precisely the type of guitar: the perfect musical companion, the guitar you won’t be able to put down. The one guitar you’ll be able to rely on every time and will find yourself reaching for again and again. For years, the Les Paul Studio has been the choice of countless guitarists who appreciate the combination of the essential Les Paul features–humbucking pickups, a glued-in, set neck, and a mahogany body with a maple cap–at an accessible price and without some of the flashier and more costly cosmetic features of higher-end Les Paul models."
Now, the Les Paul Studio has been reimagined. It features an Ultra-Modern weight-relieved mahogany body, making it lighter and more comfortable to play, no matter how long the gig or jam session runs. The carved, plain maple cap adds brightness and definition to the overall tone and combines perfectly with the warmth and midrange punch from the mahogany body for that legendary Les Paul sound that has been featured on countless hit recordings and on concert stages worldwide. The glued-in mahogany neck provides rock-solid coupling between the neck and body for increased resonance and sustain. The neck features a traditional heel and a fast-playing SlimTaper profile, and it is capped with an abound rosewood fretboard that is equipped with acrylic trapezoid inlays and 22 medium jumbo frets. The 12” fretboard radius makes both rhythm chording and lead string bending equally effortless, andyou’re going to love how this instrument feels in your hands. The Vintage Deluxe tuners with Keystone buttons add to the guitar’s classic visual appeal, and together with the fully adjustable aluminum Nashville Tune-O-Matic bridge, lightweight aluminum Stop Bar tailpiece, andGraph Tech® nut, help to keep the tuning stability nice and solid so you can spend more time playing and less time tuning. The Gibson Les Paul Studio is offered in an Ebony, BlueberryBurst, Wine Red, and CherrySunburst gloss nitrocellulose lacquer finishes and arrives with an included soft-shell guitar case.
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Introducing the Reimagined Gibson Les Paul Studio - YouTube
Phat Machine
The Phat Machine
The Phat Machine is designed to deliver the tone and responsiveness of a vintage germanium fuzz with improved temperature stability with no weird powering issues. Loaded with both a germanium and a silicon transistor, the Phat Machine offers the warmth and cleanup of a germanium fuzz but with the bite of a silicon pedal. It utilizes classic Volume and Fuzz control knobs, as well as a four-position Thickness control to dial-in any guitar and amp combo. Also included is a Bias trim pot and a Kill switch that allows battery lovers to shut off the battery without pulling the input cord.
Silk Worm Deluxe Overdrive
The Silk Worm Deluxe -- along with its standard Volume/Gain/Tone controls -- has a Bottom trim pot to dial in "just the right amount of thud with no mud at all: it’s felt more than heard." It also offers a Studio/Stage diode switch that allows you to select three levels of compression.
Both pedals offer the following features:
- 9-volt operation via standard DC external supply or internal battery compartment
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Static Effectors’ Street Series pedals carry a street price of $149 each. They are available at select retailers and can also be purchased directly from the Static Effectors online store at www.staticeffectors.com.
This outing of Dipped In Tone kicks off with an exciting update from Zach Broyles’ camp: He’s opening a brick-and-mortar guitar shop in Nashville, called High Voltage Guitars. Opening on October 8, the store will carry gear from Two-Rock, Divided By 13, Dr. Z, Castedosa, Fano, Novo, and of course Mythos Pedals. Zach hints that there might be some handwired JHS pedals from Josh Scott himself, too, and Rhett reveals that he plans to consign some of his guitars at the shop.
The business side of Zach’s new venture brings them to a key piece of today’s episode: Rhett and Zach aren’t running charities. They do what they do to make money; guitars, gear, podcasting, and content creation are their literal jobs. And they’re not as glamorous and breezy as most armchair commentators might guess.
Want to do what Rhett and Zach do? Welcome to the club. The guitar-influencer field is what one might call “oversaturated” at the moment, and it’s difficult to break out—but not impossible. As our hosts explain, it requires putting in 60-hour work weeks, a diverse skillset, a knack for catching people’s attention, and a certain level of genuineness. Rhett knows this path well, and he has hard-earned advice for staying true to oneself while building a following in the gear world.
Tune in to learn why Rhett thinks Fretboard Summit, a three-day guitar festival organized by Fretboard Journal, blows NAMM out of the water and builds legitimate connections between guitarists, and catch the duo dipping a Dick Dale-inspired, all-Fender rig.
