If an American guitar amplifier from the late ’40s, ’50s, or ’60s doesn’t carry the Gibson or Fender badge, odds are high it was manufactured by Valco, no matter the name on the cabinet. More than just a big-brand jobber, though, Valco made great-sounding combos, as this Oahu 415k reminds us.

Manufactured in Chicago but given a name evocative of a Pacific-island paradise, the 415k also encapsulates a large portion of early electric-guitar history in one square, two-tone box. Wrap up the very influential Hawaiian-guitar craze of the early 19th century and its dramatic impact on popular music in the United States along with the efforts of several major innovators in the quest to properly amplify the guitar in general, and that’s what we’re looking at in the form of this unassuming amp.

The Oahu moniker dates to the popularization of Hawaiian steel guitars in the 1920s, hence the geo-specific branding. Half-brothers Harry Stanley and George Bronson formed the Hawaiian Conservatory of Music in 1926… in Flint, Michigan. The business was a three-pronged attack of sheet music, lessons, and instruments to play it all on, and they proliferated via door-to-door sales in most major U.S. cities, magazine ads, and other marketing tools. In 1930, Stanley took his branch of the business to Cleveland, opening an Oahu school and porting the name Oahu Publishing Company onto his instruments, which were often made in Chicago by Kay, Harmony, or Regal.

As the Hawaiian craze evolved from acoustic to electric instruments in the late ’30s, so did Oahu. By that time, one powerhouse in the field had moved from Los Angeles to Chicago to offer OEM services to anyone who wanted to put their name on a guitar or amplifier. So, in many ways, this 1960 Model 415k represents a natural extension of what was to come from the makers of the late-’30s Dobro featured last month.

As discussed regarding that amp, the founders of National and Dobro joined forces in the late ’20s/early ’30s and, in 1936, moved their operation from Los Angeles to Chicago, reconfiguring themselves as Valco a few years later. Named for the first initials of partners Victor Smith, Al Frost, and Louis Dopyera (with “co” added), Valco became one of the country’s largest manufacturers of electric guitars and amplifiers. Many were sold under the brand National or the more-affordable Supro, often the same guitar or amp wearing different cosmetics. But they also supplied gear for many catalog brands as well as for a few significant name brands, Gretsch among them, and of course for Oahu.

The Oahu 415k, therefore, was right in the Valco wheelhouse for 1960, and – unsurprisingly given the maker’s modus operandi – is much the same amp found elsewhere dressed as a Gretsch, National, Supro, Airline, or any of a few other brand names and models. Most notably, perhaps, other than in its appearance, it’s virtually the exact same amp as the desirable Supro 1624T, and entirely the same circuit. Other than looks and brand name, the differences are mainly in the speaker complement, though the owner of this example, Leon Chalnick, has changed the original elliptical 6″x11″ speakers for a single 12″ that brings it even closer to the Supro’s feature set. Otherwise, the two share an output rating of around 18 watts derived from a pair of rather unusual yet muscular-sounding 6973 tubes, with standard 12AX7s in the front end for preamp, tremolo, and phase-inverter duties.

Inside, the 415k reveals a spaghetti junction of wiring strung along a series of terminal strips. Apply a sharper focus, though, and you’ll find the workmanship is rather tidy with a certain linearity and logic to the design, allowing Valco’s engineers to squeeze a simple (yet highly functional and characterful) circuit into a small space. One of the maker’s signature touches is the ceramic disk coupling caps where we’d normally find larger axial (a.k.a. tubular) coupling caps in more-elevated brands. The relatively low voltages found in several stages of the amp, however, allow such caps to thrive, and those components contribute a slightly granular texture and harmonic thickness to the amp’s sonic personality.

Because of their tall, narrow shape and smaller nine-pin sockets, many assume 6973 output tubes are similar to EL84s. But, they use different pin connections and therefore cannot be substituted one for the other, and they also have quite different specifications and sonic characteristics. The 6973 has a maximum plate-voltage rating of 440 volts DC compared to the EL84’s 350 volts and different bias requirements. The robustness of this tube indicates you can get a little more power out of it, too, and they were often used by jukebox manufacturers of the ’50s and ’60s. Most guitar amps that used them rarely pushed them to maximum capabilities, and running at around 350 volts DC on the plates in the Oahu, they put out a solid 18 watts or so, with a full, round, chunky demeanor.

“I tend to like amps that not only produce the clear, unadulterated sound from the guitar, but which are also capable of producing great overdrive on their own without pedals,” says Chalnick. “This one definitely qualifies! It’s one of the best-sounding small amps I’ve ever heard. I wasn’t crazy about the two elliptical 6″x11” speakers, so I’ve been using an Eminence Alessandro GA-SC64 12″, and it’s like the speaker was made for this amp. In fact, it’s the exact cabinet that Valco used for the legendary Coronado, used by Jimmy Page on Led Zeppelin and the solo to ‘Stairway to Heaven.’ I think the larger cabinet really enhances the sound, giving it a bigger and firmer bottom end.”

Add the deeply pulsing bias-modulating tremolo to the robust sonics and killer retro looks, and it’s a fantastic alternative-vintage package at a price still relatively accessible compared to more-collectible names, and certainly giggable in the right setting.

This article originally appeared in VG’s August 2024 issue. All copyrights are by the author and Vintage Guitar magazine. Unauthorized replication or use is strictly prohibited.