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Even once it was accompanied by the full range of brownface models, as it was by the time of our featured example’s production, the Vibrasonic was built as the biggest and beefiest of Fender’s 50-watters, though almost every feature was also shared by another of its siblings.
Its schematic was identical to that of the Concert, Pro, and Super of the era; the Concert, Twin, and Vibrasonic used the same robust power transformer, while the Twin and Vibrasonic had the same output transformer (the change of speaker load from four ohms in the Twin to eight ohms in the Vibrasonic ably compensated for the move from four 5881 output tubes to two, respectively).
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By design, the Vibrasonic was an amp for serious players who wanted to be heard, and in 1962 – from Fender’s perspective, at least – that still equated to maximum clean power and punchy, cutting tone, the kind of thing equally suited to reproducing pedal-steel guitar as to the firm Telecaster (or even Jazzmaster) twang of Luther Perkins.
Today, however, many players are more likely to be enamored of the earlier grind that the Pro’s smaller output transformer elicits into its Jensen speaker.
Despite all of its major “firsts,” the feature about which players tend to rave most is something else the Vibrasonic has in common with its mid- and larger-sized brownface compadres – its tasty harmonic vibrato.
This effect started in 1959 as a complex circuit using a full two tubes (that’s four individual triodes) to induce a phasey wobble on the signal of one of the amp’s two channels.
Moreover, as the first amp in Fender’s new Professional series, it was intended to be just that.Lovers of true tremolo might find it soft and burbling compared to the rhythmic chop of true tremolo – a circuit much easier to render in most guises – but it is a dramatic and hypnotic sound in its own right, and one that can quickly become addictive.As the brown amps evolved into the blackface range in late 1963 going into ’64, this complex pseudo-vibrato was lost to a simpler true-tremolo circuit that required just one preamp tube plus an opto-cell network.Depending on when the speakers were made this information may simply include a year and week or may be more specific, down to the day or hour.Carefully turn the speakers around so that the back of the speaker is facing you.