Marshall and Softube first collaborated on the JMD:1 series of guitar amps which were released in 2010. In 2014, Marshall Amplification and Softube entered a long-term partnership and the first product from this collaboration is the Marshall Plexi Super Lead 1959, exclusively for the UAD-2/Apollo platform and will be out in May 2015.
The particular amplifier that Softube modeled and based the UAD-2/Apollo plug-in on is not just any Marshall Plexi. In the making of this plug-in, Softube worked closely with Marshall's product expert Chris George, who lent Softube this amp from Marshall's own "museum" which isn't open to the public. This very amp, built in 1967 and kept in pristine shape is Marshall's own reference to how a Plexi should sound.
But the sound of a guitar amp doesn't just come from the amp itself. The cabinet choice, microphone selection and microphone placement are also vital parts in getting that sound. Therefore, Softube used the expertise of legendary engineer Tony Platt for the cabinet and microphone simulation. Tony's credentials speak for themselves. Among many other fantastic records, he engineered AC/DC'sHighway to Hell and Back in Black. It's safe to say Tony knows better than most how to record a loud Marshall amplifier.
The goal for this plug-in was to capture how the Plexi sounded when it was new back in 1967, to get the sound Jim Marshall himself intended. To capture the typical late sixties tone, Tony and Chris chose to use a straight 1960BHW 4x12 inch speaker cabinet, loaded with Celestion G12H-30's. These are relatively low wattage speakers, similar to those used at the time, which will saturate more easily compared to more modern constructions. This adds a lot of character to the end result. The particular speakers in this cabinet were not from the sixties, as speakers that have spent nearly 50 years reproducing the sound of 100 watt guitar amplifiers will have deteriorated and give a much different sound compared to what was intended. The speakers used had however been well broken in to reach their full potential and liveliness.
Tony chose to make three different microphone sets with three microphones in each—two close mics and one room mic. The user can open the plug-in's side panel where an easy to use channel strip appears. Here, the user can select between the three sets of microphones and adjust the individual microphone levels and panning. The settings are named FET, Valve and Dynamic to indicate what microphone types were used.