Guytron's flagship model is the GT100-FV and it has been shipping since 2003. But for those of you who may not know this already, it is actually a (multi-voiced) version of the original GT100 amp from 1995. There are some other refinements as well such as the stainless steel chassis, fully enclosed for low noise, etc. 

The manual can be downloaded below. 

​Download Basic GT100 manual
* Original 1997 GT100 Owners Manual (Pre F/V)

Download Tube Chart And Block Diagram
* Shows which tube does what. Good for tube swapping!

​Download F/V Addendum
* Describes the basic effects and operation of the new F/V module switches.