By Mitch Colby Numerous terms related to guitar amp construction, features, and history are commonly misunderstood and misused.
Let’s start with the following four: Point-to-point wiring: True point-to-point wiring (sometimes abbreviated “P2P”) uses rails, which are also known as terminal lug strips, without any circuit board.
Supro amps were actually built by Valco, which was based in Chicago and also made amps under various other brand names, including Airline, Gretsch, National and Oahu.
Most Supro amp models weren’t quite powerful enough for use on stage and were rarely used in concert by big name acts, although Jimi Hendrix played guitar through a Supro bass amp in clubs with the Isley Brothers, Ike Turner and Little Richard.
When fully driven into overdrive or distortion they could easily put out 150 or more watts, so naturally they sound louder than a distorted amp with peak power of 100 watts.
Plexi: The Marshall “plexi” era dates from around 1965 through the end of 1969, not including reissues.
Starting in the late Sixties many guitarists put Supro amps to good use in the studio for their distinctive and attractive distortion tones.
Jimmy Page famously used a Supro combo with a single 12-inch speaker on the first two Led Zeppelin albums.
The “plexi” panel is a plastic called Perspex, the trade name for an acrylic material also known by the trade names Acrylite, Lucite, and Plexiglas.While these are very cool amps, they are not “plexi”!During the Fifties and Sixties, Supro established a niche as a more affordable alternative to the guitars and amps available from music industry leaders like Fender and Gibson.“Plexi” does not mean see-through, but rather it is a description for a Perspex panel that is painted gold and has black lettering.Marshall amps built before the “plexi” models had either white panels or lettering that was screened directly on the aluminum chassis.FEATURES All three models are combos, but each offers a different tube complement and speaker configuration.The Dual Tone is a 24-watt amp featuring two 6973 power tubes and four 12AX7EH preamp/tremolo circuit tubes.Numerous terms related to guitar amp construction, features, and history are commonly misunderstood and misused.In fact, there are so many that it will take more than one Circuit column to cover just the ones that are most important to amp collectors.Most vintage amps made by Valco (which includes the brands Gretsch, Montgomery Ward/Airline, National, Oahu, Sears/Silvertone, Supro, and more) were constructed this way through the mid Sixities, and some of the larger vintage Silvertone amps have wiring that is particularly messy.More recently, Matchless amps (made by noted Valco amp aficionado Mark Sampson) were wired this way.