These are very rare on this side of the pond, they're not cheap to get hold of! Great fun for a non-invasive, easy-to-install, fully reversible way of modding Marshall and other amps. I've sold the JCM800 Studio head that I bought this for, so no longer have a use for it. It's in great condition. Comes with a print out of the installation instructions. Check out the videos online too - and I'd suggest checking the Legendary Tones website for guidance on compatibility. This one is the Standard wiring. Happy to post, including with global shipping programme - or collect in person, London N11. cheers!
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