Hey Folks - been awhile.  I built my OTS last Feb/March and had it working beautifully within a week or so - only issues were a missed ground and swapping the OT primaries -- nasty oscillations there man. 

I want to try a pair of these Valve Art KT66s in my OTS.  These are real nice sounding, big-bottle (replicas actually) tubes - they work real nice in my JTM45/Bluesbreaker...  Anyway - I think I know my stuff (built 7 amps now, incl. reverbs, buffered loops, 4 el34, etc varieties) well enough to do this and check that it is ok.  The main issue is a typical KT66 wants 1500 ma on the heaters (varies twixt brands), while the 6L6 uses closer to 900 ma current.  I THINK the OTS' power tranny has plenty current to spare (nik - is the same pt for the 100 watt OTS?  If so, I have my answer).  Simple matter of installing them and checking the heater voltage to see if it drops any/much, I believe.  Thinking that an inadequate heater supply would end up delivering 6 volts or less if overloaded - yes?   As far as bias --- 60 to 70% of max. for nice BIG clean - closer to 75% max diss. for BIG dirty (think bluesbreaker I think)...  bias not a big problem -- ensuring the extra heater current required is available is the main issue in sub'ing KT66 for 6L6.  What say ye fellow builders and tinkerers?

Cheers and thanks, Stephen

Great Clip!  Thanks too for the mod layout, makes things really clear.  So - I built my OTS in early April (completed 04/08), my kit was based on the 12/07 layout - so I did the 220k pre-od-trimmer mod with pretty nice results, but .. think I will try the added mods you've done.  I was on T.A.G. and saw Gil and Scott's posts, but I don't recall the PS Filter beef-up (basically to 75uF from 50uF I think), also somehow missed the OD cathode cap/resistor mods and plate resistor increases.  I thought maybe you were going for ODS #124, but see that's not it.  I guess I just missed the threads where these mods were discussed, so I really really appreciate you posting and doc'ing them here.  I can imagine the PS mods smooth things more, and the also bringing the OD plate voltages down some more should help (even after the 220k mod I did, I have more gain than I'll ever want here).  I am jazzed about trying these out - the soldering iron is warming up forthwith!

Cheers and thanks again - I still have to post my own little build thread with some pix soon.  I really want to get a new cab, or mod mine, like one picture I saw where the top is cut out and there's a plexiglas panel over the circuit - so you can see this work-of-art ODS guts without tearing her open.   I imagine most folks have seen that amp.  A real monument to HAD and the ODS.

Stephen