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  • If treble and bass are not enough, go the whole hog and build yourself a treble/mid/bass tone stack equipped beast. If you’re into mids, the W.I.S.C GT5 ‘Halcyon’ is a tone fiddler’s dream. You would think that adding a mid pot is straight forward. However, when we are talking active Baxandall stacks, nothing is simple and everything is a compromise. After a complete stack overhaul, I think I got pretty close to the frequency response of the GT5 ‘Classic’. 

    Even with an extra pot you still get 13db and -19db of treble boost and cut respectively. Because of the truck load of bass in the circuit, 4db and -22db of respective bass boost and cut was perfect. Keeping in mind that mid frequencies around the 1kHz range are super sensitive to the ear, a mid cut and boost sweep range of 9db is nearly bang on. And just so you can check the treble/mid/bass tone stack frequency response out for yourself, I’ve included a set of plots that represent the full sweep of the stack. 




    The W.I.S.C GT5 ‘Halcyon’ full plans pack includes: 

    • a schematic/circuit, 

    • detailed layout diagrams accomodating for either a 120v or 240v mains primary, 

    • a detailed turret board layout, 

    • a key for the colour coded turrets,

    • a transformer cable termination guide,

    • chassis layout diagrams of both top view and bottom view, 

    • a front and rear chassis panel layout, 

    • schematic codes, 

    • a resource item list, and 

    • tone stack tweaker’s guide. 


    A little Bit More on The Active Baxandall Stack 


    I personally believe that a Bax stack knocks the socks off anything else but I can see why they perhaps generate a bit of frustration. They are ultra sensitive, and you have to work pretty long and hard to achieve a perfect balance. They rely on feedback to each pot and so every little tweak has an affect on the whole stack. Looking back at the time I spent tweaking, I can understand why one would throw in the towel and opt for the simple circuit of the classic Fender/Vox/Marshall. I’m sure glad I persevered however, as its like the Holy Grail once you nail it. In this case, I’ve done the hard yards for you, so you can have peace of mind that the GT5 ‘Halcyon’ has your back. 


    The GT5 ‘Halcyon’ is built with the same pre-amp as the GT5 ‘Classic’ however they are quite different amps. The ‘Classic’ is raw power with every once of frequency ringing through the treble and bass pots. The ‘Classic’ was hard to tame truth be told. I nearly threw in the towel by just whacking in a 12AU7. But we are better than that people! In comparison, the extra mid-pot of GT5 ‘Halcyon’ calmed things down all by itself, leaving the perfect balance between grunt and refinement. It’s an amp that I’m very fond of, and I will be building another one for myself very shortly. 



    The W.I.S.C GT5 ‘Halcyon’ Full Plans Pack is designed for those folk who really need tone. It wouldn’t hurt to be pretty handy with a soldering iron as well. For those requiring an insurance blanket, a comprehensive video series of the GT5 Halcyon build is only a click away. Also check out the Blog page if you want to dabble in meta physics. 


    Have Peace of Mind 


    As with all my designs, if things don’t go as planned for whatever reason, be sure to grab yourself a ‘no questions asked’ full refund! 

    W.I.S.C GT5 'Halcyon' Full Plans Pack

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