Grab the entire Amp Plans Collection enchilada. The Diesel/Turbo S5 Mark I and S5 Mark II, the GT5 ‘Classic’ and GT5 ‘Halcyon’, and the GT18 'Paydirt'. That’s over 100 Meg worth of plans (Megabytes not Ohms).
Choice is everything and the entire Amp Plans Collection has got you covered. If you’re into no-nonsense tone with nothing to get in the way, the S5 Mark II is for you. If you aim to test your skills a bit more with some width and compression switching, then the S5 Mark I is the go-to. Maybe you’re at peace with your soldering iron and want more control over your tone. In that case, opt for one of the GT5 series. Each GT5 model includes an active Baxandall type tone stack. The GT5 ‘Classic’ (Treble/bass) has a heap of gain and treble to burn. The GT5 ‘Halcyon’ (treble/mid/bass) adds a mid pot to the mix for the ultimate transcendental tone tweaking trilogy. If you are looking for a JCM800-ish tone with a usable tone stack and an uncompromised clean channel, then step up to the GT18 'Paydirt' in push-pull. The cathode biased 'Paydirt' boasts an active Baxandall stack with just the right amount of filtering for that blues/rock nirvana of the 80's.
Never be Afraid to Fiddle
To comprehensively nail your tone, check out the frequency curve plots that are included in the GT5/GT18 plan packs. Within those frequency responses you may find the sweep of your dreams. If the GT5 ‘Classic’ is right up your alley, lock in a mid frequency by changing the value of just one capacitor. Now go forth and fiddle!
I would never leave you hanging so check out the comprehensive video series of the S5 Mark I and GT5 Halcyon builds which offers handy hints and building tips. Everything is covered, from chassis construction to making your own cables. There is even a vid about making your own composite board. Also check out the Blog page if you want to go down the theory road.
As always, I understand that things can go south pretty quickly regarding circuits. If you feel like you’re in too deep and need to pull the pin for what ever reason, holla for a ‘no questions asked’ full refund.