Different OPT configurations:
U0(S1-S2): 6.9V
U0(S3-S4): 7.0V
U0(S5-S6): 5.5V
U0(S7-S8): 383V (normally not used)
UprimX4: 460V (normally used as primary input which enables optional 50% UL-taps)
UprimX4+S7+S8: 1226V (845 only, equals maximum 613V@20Hz transformer drive)
 
Total primary load (KT66/807/PX25): 
10000
Ohm a-a /2Rk=305Ohm@438V/60Vp-p drive/Put=250X0.11/2=14W
Total primary load (KT88/6550): 
5000
Ohm a-a /2Rk=430Ohm@443V/70Vp-p drive/Put=250X0.2/2=25W
Total primary load (300B): 
5000
Ohm a-a /2Rk=800Ohm@480V/110Vp-pdrive/Put=250X0.2/2=25W
Total primary load (6C33): 
2400
Ohm a-a /2Rk=550Ohm@410V/160Vp-p drive/Put=240X0.4/2=48W
Total primary load (845): 
14000
Ohm a-a/2Rk=1.6kOhm@960V/180Vp-p drive/Put=520X0.15/2=39W
Impedance matching:
connection
U0
prim.load
Rl(S1&S2)
Rl(S3&S4)
Rl(S5&S6)
opt.load
sec.load
tube.type
(S1+S3)//(S2+S4)
9.83
10000
2.25
2.32
1.43
4.57
4
KT66/807
S1+S5
12.40
10000
2.25
2.32
1.43
7.27
6
KT66/807
S1+S2
13.80
10000
2.25
2.32
1.43
9.00
8
KT66/807
S1+S2
13.80
5000
1.13
1.16
0.71
4.50
4
KT88
S1+S5+S6
17.90
5000
1.13
1.16
0.71
7.57
6
KT88
S1+S2+S5
19.30
5000
1.13
1.16
0.71
8.80
8
KT88
S1+S2
13.80
5000
1.13
1.16
0.71
4.50
4
300B
S1+S5+S6
17.90
5000
1.13
1.16
0.71
7.57
6
300B
S1+S2+S5
19.30
5000
1.13
1.16
0.71
8.80
8
300B
S1+S2+S5
19.30
2400
0.54
0.56
0.34
4.22
4
6C33
S1+S2+S5+S6
24.80
2400
0.54
0.56
0.34
6.98
6
6C33
S1+S2+S3+S4
27.80
2400
0.54
0.56
0.34
8.77
8
6C33
S1+S3+S4
20.90
14000
0.44
0.46
0.28
4.07
4
GE845
S1+S2+S3+S4
27.80
14000
0.44
0.46
0.28
7.20
6
GE845
S1-3+S5-6
31.80
14000
0.44
0.46
0.28
9.42
8
GE845

6 Ohm load generally not optimized (substraction may also be used). Optimum load is generally higher than used load. This is due to excessive loss in this transformer prototype.Using the UL-feature, generally doubles plate resistance while optimum plate load is approximately the same.

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