WhitakerAudio JC Whitaker 20 W Stereo Integrated Audio Amplifier, Manual

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183
20 W Stereo Integrated Audio Amplifier
Selected tube parameters are listed in Table 10.2.
Table 10.2 Key Parameters of the 6973
General Characteristics
Heater (ac/dc) 6.3 V, 0.45 A
Heater-cathode voltage
Peak value ±200 V max.
Average value 100 V max.
Direct interelectrode capacitance
Grid to plate 0.4 pF max.
Grid #1 to cathode, heater, grid #2, grid #3 9 pF
Plate to cathode, heater, grid #2, grid #3 6 pF
Push-Pull Class AB
1
Amplifier, Maximum Ratings (Design-Maximum Values)
Plate voltage 440 V
Grid #2 (screen grid) voltage 330 V
Plate dissipation 12 W
Grid #2 (screen grid) input 2 W
Envelope temperate, at hottest point 250ºC
Push-Pull Class AB
1
Amplifier with Grid #2 of Each Tube Connected to Output Transformer Tap
Design Maximum Values
Plate and grid #2 supply voltage 410V
Plate dissipation 12 W
Grid #2 input 1.75 W
Envelope temperature, at hottest point 250ºC
Typical Operation with Fixed Bias (values are for two tubes)
Plate supply voltage 375 V
Grid #2 (screen grid) supply voltage Note 1
Grid #1 (control grid) voltage –33 V
Peak AF grid #1 to grid #1 voltage 67 V
Zero signal cathode current 62 mA
Maximum signal cathode current 95 mA
Effective load resistance (plate to plate) 12.5 k
Ω
Maximum signal output 18.5 W
Note:
1 Obtained from taps on the primary winding of the output transformer. The taps are located on each side
of the center tap (B+) so as to apply 50% of the plate signal voltage to grid #2 of each output tube.
NC
H
H
P
2
G
1
G
1
G
3
K, G
2
G
Legend:
H = heater
K = cathode
G = grid #1, 2, 3
P = plate
1
2
3
4
5
6
7
8
9
Figure 10.4 Terminal pinout of the 6973.