Hi guys, I've been a bit keen on these for awhile and some nice 6L6GC came my way. The original Thunderbolt S6420 is a simple circuit so that pleases me and the end result should see it rifting away to some awesome LED ZEP tones. I have modded the circuit as the original had a spare triode at the input stage. So looking through some of the other Supro schematics, I found the S6424 input a good fit. A neat mod at the input jacks will allow the original S6420 circuit to be played and the second channel S6424 circuit and a link jack to blend the two. Some of the component values have been changed to todays values and some are just what I have on hand.