About our SST-108:
The original 108 output transformer was standard fitment on several different amplifiers in Fender's catalog during the late 1950s. This includes the Harvard (some of them), Tremolux, Vibrolux, and of course the Deluxe amps ranging from around 1957 till sometime during 1959. It's an odd design for Leo Fender to pull out of a catalog for a push-pull amplifier at the time - a decision most likely due to Triad's ability to produce them in great numbers and the low cost offered to OEM manufacturers back in the day.
What's unique in it's design is what makes it unique in it's sound. First unlike any other transformer Fender had used on their Deluxe amplifiers previously, it's wound on a plastic bobbin with a random wound primary. This technique reduces leakage inductance in the primary opening up the top end more from the earlier layer wound 1839 (later Triad 50246) used on the Deluxe amplifier at the cost of higher winding capacitance. Secondly, it's laminated with a shimmed butt stack in the core - a technique normally reserved for single-ended operation. This has the effect of reducing primary inductance at larger signal swings which in turn will reduce the low frequency content when the amp is cranked up loud. Wound for the discerning amplifier builder.
We’ve opted to terminate what would have originally been a "self lead" on the secondary common to a wire lead to prevent any chance of a floating ground occurring. Aside from this minor change, the SST108 is easily the most vintage accurate output transformer available for your 5E3 build or repair!