The high-end of Gibson''s postwar amplifiers, the GA-CB is now one of the rarest vintage amps around.
Introduced in 1948, the Custom-Built led the new Gibson postwar amplifier line that included the GA-20, GA-25, GA-50, and GA-75. At this time, Gibson was undergoing a complete overhaul under the guidance of new president Ted McCarty. The BR line, a rush introduction intended to get Gibson back on the amp market in the first days after WWII, was on its way to oblivion, save for the diminutive, yet popular, BR-9. The new Gibson GA-series amps were designed by Seth Lover and Walter Fuller and, in a first for Gibson, built entirely at the Kalamazoo plant (with the exception of some cabinets built by an outside vendor). Offering amps was more than perfunctory for Gibson. The company had been in the amp business longer than almost anyone else, since 1933, and considered it a necessary part of the business of selling electric guitars. So although amp production was, in comparison to guitar, a secondary task at Gibson, it was nevertheless treated it as serious business.
|Photos: Lynn Wheelwright|
The GA-CB was by far the most powerful, sophisticated, and expensive amplifier Gibson had ever built. It did, however, have a number of features one might expect on a pre-war amp. Most noticeable is the bottom-mounted chassis with rear-facing controls. This configuration was fine in the days when players mostly sat down, placing their amps in front of themselves. But in the late ‘40s, players were beginning to stand up more during performances, creating demand for easier access to control panels. In 1948, the GA-20 and GA-75 were Gibson’s only amps to offer top-mounted chassis with top-mounted controls. The GA-CB’s heavy-duty chassis held dual-6L6 power tubes that produced a little over 40 watts of power. The rest of the tube complement consisted of two 6J5, two 6S87, three 6SJ7 and a 5T4 rectifier. Controls were bass and treble, frequency and intensity for the Lover-designed tremolo circuit, and individual gain knobs for both the instrument and microphone channels.
The Custom-Built was covered in brown leatherette with green fabric pinstriping and a gold Gibson logo. The speaker opening consists of six vertical slats cut into the solid front of the cabinet with diamond- patterned grille cloth covering theopenings. Gibson would later realize that this type of speaker opening restricted speaker output and change to an opengrille format. The cabinet itself was large, a full four inches deeper than the next largest Gibson, the GA-75. While many of the Class of ’48 Gibsons were shallow rectangles resembling suitcases, the GA-CB seems almost a cube. The extradeep cabinet somewhat resembles a late- ‘40s Jensen Imperial Hi-Fi speaker, and it provides ample room for the brown-frame 15” Jensen Concert Type H Coaxial driver, of which Gibson claimed a “50 to 15,000 cycle range.” Incorporating a tweeter unit mounted inside the woofer, the Type H speaker was designed for use in Hi-Fi stereo systems. McCarty and Lover were wellknown Hi-Fi buffs and considered what was good for Hi-Fi to be good for guitar as well. This attitude is further in evidence by the presence of a Jensen four-position High Frequency Control unit located at the upper back of the GA-CB. The rotary control has four positions, at 10, 11, 1 and 2 o’clock (although it will hold at the 12 o’clock position as well).
Also offered on the higher-end models of Jensen home speakers, the High Frequency Control served to either impede or free the flow of upper-frequency signals to the driver. Coming in at 60 pounds, the GA-CB is fully double the weight of the GA-75. The added weight is a product of the heavy-duty driver, the larger chassis, the sturdy transformers, and the obvious heft of the cabinet wood.
In design, construction, price and tone, the GA-CB was beyond almost any other amplifier of the time. In fact, the GA-CB may have been the most advanced guitar amplifier of the early 1950s. In comparison to the Fender Pro, an amp that also featured dual 6L6 power tubes and a 15” speaker, the GA-CB has more power, more features and a higher-quality driver. Where the Fender beat the Gibson hands-down is in its guitar-specific voicing. Fender had learned that players were looking for a new, unique tone, something different from the sounds of the ‘30s. Gibson hadn’t gotten this message yet. While they may have been building higher-end amplifiers, they still had not moved significantly away from using lightly-modded PA circuits for their guitar amplifiers. Additionally, the entire Gibson team ascribed to a sound ideal that was smooth, mellow, and, above all, 100 percent distortion-free.
With the combination of higher power, a tremolo circuit, and the Jensen-designed High Frequency Control, Gibson offered with the GA-CB a package aimed squarely at the professional player. In advertisements of the time, Gibson touted the GA-CB as being “superlative for studio work, for church or auditorium use.” Cleary not an amp for greasy kids, twanging cowboys, or hard blues. By the end of its production run in 1953, only 108 GA-CB amps had been built. At $425 the GA-CB was a very expensive piece of equipment. Using the Consumer Price Index calculator, the GA-CB would cost today roughly $3835, a price similar to some of the currently available boutique, custom and high-power amplifiers. As for finding an actual GA-CB, few are known to exist. Even major collectors just shake their heads “no” when asked if they have a Custom- Built. Some recall an opportunity to buy long past, but most have never even seen one. The amplifier shown in these photos belongs to the collector and historian Lynn Wheelwright. Lynn found this amp online about ten years ago. A clean example such as this is almost unheard of, so it is an added bonus for gear fans that this particular amplifier will be on display at the Museum of Making Music in Carlsbad, CA, through March, 2010, as part of the exhibit: ON! The Beginnings of the Electric Sound Generation.
Wallace Marx Jr. is the author of Gibson Amplifiers, 1933-2008: 75 Years of the Gold Tone.
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Created in collaboration with legendary guitarist George Lynch of Dokken and Lynch Mob fame, the Mr.Scary Mod adds an adjustable tube gain stage and an onboard Deep control, which together are designed to enable an amp to have increased sustain while still retaining note definition and dynamics.
LegendaryTones, LLC today announced production availability of its new Mr. Scary Mod, a 100% pure tube module designed to instantly and easily expand the capabilities of many classic amplifiers with additional gain and tone shaping. Created in collaboration with legendary guitarist George Lynch of Dokken and Lynch Mob fame, the Mr.Scary Mod adds an adjustable tube gain stage and an onboard Deep control, which together are designed to enable an amp to have increased sustain while still retaining note definition and dynamics.
Originally released as the Lynch Mod in February 2021, the updated Mr. Scary Mod features the same core circuit as the Lynch Mod but is now equipped with a revised tube mix combo per George’s preference as well as a facelift in a newly redesigned electro-galvanized steel enclosure. As with the Lynch Mod, each run will be limited and the first run in Pumpkin Orange with Black hardware is limited to just 150 pieces worldwide.
The Mr. Scary Mod adds an adjustable tube gain stage on top of the cathode follower position, keeping note definition and articulation while further increasing sustain. Each Mr. Scary mod is meticulously built by hand in the USA, one at a time, and tuned using high-grade components. Equipped with a single ECC81 (12AT7) in the first position and ECC83 (12AX7) in the second, the Mr. Scary Mod can clean up beautifully when rolling down your guitar’s volume, and still adds scorching gain when you roll it back up. This is a gain stage that’s been tuned and approved by the ears of the maestro George Lynch himself.
“The Mr. Scary Mod excels with dynamics and is incredibly touch-responsive, allowing me to shift from playing clear, lightly compressed cleans to full-out aggressive sustain and distortion –and control it all simply by varying my guitar’s volume control and picking,” said GeorgeLynch. “In many ways, it’s an old-school approach, but it’s also so much more natural and expressive in addition to being musically fulfilling when you can play both the guitar and amp dynamically together this way.”
The Mr. Scary Mod installs in minutes, is safe and effective to use, and requires no special tools or re-biasing of the amplifier. Simply insert the module into the cathode follower preamp position of compatible amplifiers (includes Marshall 2203/2204/1959/1987 circuits) and
immediately get the benefit of enjoying a hot-rodded amp that delivers all the pure harmonic character that comes with an added pure tube gain stage. The handmade in the USA Mr. Scary Mod is now available to order for $319.
For more information, please visit legendarytones.com.
October Audio has miniaturized their NVMBR Gain pedal to create two mini versions of this beautifully organic-sounding circuit – including an always-on gain device.
The NVMBR Gain is a nonlinear amp that transitions gracefully from clean boost to overdriven tones. Volume increases from just over unity to about 10db before soft-clipping drive appears for another 5db of boost. Its extraordinary ease of use is matched by outstanding versatility: you can use it as a clean boost, push a stubborn amp into overdrive or create a just-breaking-up sound at any amp volume.
October Audio’s new family of mini NVMBR Gain pedals includes a switchable version that allows you to bypass the effect: one option features brand logo pedal graphics, while the other sports a fun “Witch Finger” graphic with a Davies knob as the“fingernail”.
The second version in the new lineup is an always-on device featuring the Witch Finger graphic and Davies knob, with the same NVMBR Gain circuit that lies at the core of the switchable version.
- Knob controls gain and clipping simultaneously
- Stunning silver hammertone finish
- Switchable versions are true-bypass, available with classic or witch finger graphics
- Authentic Davies knobs, including the “fingernail”
- 9V center negative power supply required
- Dimensions: 3.63 x 1.50 x 1.88 in
Witch Finger (always on NVMBR Gain) demo
All October Audio pedals are assembled in Richmond, VA, and available for purchase directly through the online shop. Street price is $109 for NVMBR Gain footswitch versions and $89 for the always-on device.
For more information, please visit octoberaudio.com.