Thanks Gregg 
I figured as such since I saw the wires from the input running to it but I thought I'd ask anyway

Just a curiosity, what is the wall mounted trimmer for and what does it do (wait is that redundant??? No no, ok good)
You know, the one next to the input jacks...

Just curious!  Thanks

Hey guys!  I dropped the Jan Phillips 12at7 into the PI spot and I noticed more sensitivity, more sustain and honestly didn't notice all that much volume drop... 

Also, gotta say to an earlier post in warning of KT66s.  (Add your "I told you so" here) They are Really big an do add warmth...  What I've ended up doing is...
-dropping the bass to almost 0
-raising the Treble to 9
-Mid is at 6
-vol at 7
-gain 10
-ratio 7 (but needs to come down to 6 or so {due to 12at7 I assume})
-presence 10
--cable in FET
--jazz on (verdict is still out on this - helped smooth the cleans a bit but that may be obtainable by just rolling back "vol" on guitar)
**SG with P90s thru 4x12 Marshall**


This is not the fuzzy tone a lot of guys buy this amp for but it is a SICK classic rock tone somewhere between a Fender and a Plexi that is just sweeeeet and full of harmonics!
Perfect tone if you really want your guitar to sing in Allman Bros, Govt Mule, Steppenwolf (though Steppenwolf is really trebly) kind of rock n roll!

Ok, here's an update!

I put the KT66 Gold Lions in and WOW!  More depth, articulation, bit more sustain, smoother, and a deeper/richer tone.  Really to my ears it's almost like crossing a 6L6 with an EL34... 

I set the bias to around 33~34mV which is roughly 60%

Overall it feels more lively

(Next step, change PI out to Jan 12at7)

Specs and settings:
V1: Amperex - Holland 12ax7a
V2: RCA - 12ax7a
PI: tung sol - 12ax7
Output tubes: gold lion KT66

Bright: off
Deep: on
Rock: on
Vol: 7
Tone: 8
Mid: 6
Bass: 3
OD: 10
Ratio: 7
Presence: 10

Guitar: SG standard w/ Phat Cat P90s and rewired internals to the '59 Les Paul circuit
Cab: 4x12 Marshall very clean high wattage speakers

Oooo so I know this was a dead post but no one actually answered the OP question directly (as far as I saw) the answer is that I do have the TC Hall of Fame and run it through the effects loop with no buffer because the pedal was specifically disigned to do so and it sounds wonderful!!!
.

Hope this helps any future readers

I've seen the KT66 mentioned here a handful of times but there has never been a follow up on any of those threads.  One guy even said his were running a little hot even after turning the bias as low as he could...  No reply to his post.

I'm just curious because I ordered a pair hearing rave reviews about them in general and would like to know what others think or problems they've run into.

Thanks much guys!!!