Check the listing for details. Synergy Marshall JCM 800 Preamp Module. Condition: New. Listed at 449.99 USD. Double the JCM Fun The JCM 800 debuted in 1981 and was immediately responsible for blowing more roofs off of clubs and stadiums than perhaps any other amp of the era. Now, the Synergy Marshall JCM 800 encapsulates this iconic roar into a convenient 2-channel preamp module, enabling you to harness the British-infused master-volume voice used by influential players such as Slash, Zakk Wylde, Jeff Hanneman, Kerry King, KK Downing, Glenn Tipton, and many more. Loaded with three 12AX7 preamp tubes, the Synergy module injects your playing with the same aggressive midrange bite, tight low end, and crisp highs as the full-size amplifier. Moreover, the built-in Zero Watt power amp section allows it to replicate the original amplifier's phase inverter circuitry.