12AX7 Application Data (mu = 100)
Class 	Va 	Vg1 	Ia 	Ra 	S
Triode 	100 	-1 	0.5 	80,000 	1.25
Triode 	250 	-2 	1.2 	62,500 	1.6

12AU7 Application Data (mu = 17)
Class 	Va 	Vg1 	Ia 	Ra 	S
Triode 	100 	0 	11.8 	6,250 	3.2
Triode 	170 	-4.0 	10.0 	7,200 	2.5
Triode 	200 	-5.5 	11.0 	7,200 	2.5
Triode 	250 	-8.5 	10.5 	7,700 	2.2

12AT7 Application Data (mu = 60)
Class 	Va 	Vg1 	Ia 	Ra 	S
Triode 	100 	-1 	3 	16,500 	3.75
Triode 	170 	-1 	8.5 	11,000 	5.9
Triode 	200 	-1 	11.5 	10,500 	6.7
Triode 	250 	-2 	10 	11,000 	5.5

6V6GTA
Class   Va      Vg1     Ia      Ra      S  mu   Rp
Triode  250                     1960    5  9.8  5k

6SN7-GTA Application Data
Class 	Va 	Vg1 	Ia 	Ra 	S
A 	250 	-8.0 	9.0 	7,700 	2.6
A 	90 	0.0 	10.0 	6,700 	3.0


http://www.angelfire.com/electronic/funwithtubes/Amp-Feedback.html
http://www.diyaudio.com/forums/tubes-valves/72536-el84-amp-baby-huey.html

http://www.diyaudio.com/forums/tubes-valves/140699-anti-triode-sepp-how-do-best.html

http://www.thermionic.info/

http://www.areyouexperienced.net/Marshall-JTM45-Reissue-Mods.htm

http://metroamp.com/store/index.php?main_page=product_info&cPath=44&products_id=331

http://www.talkbass.com/wiki/index.php/Fearful