181
20 W Stereo Integrated Audio Amplifier
For certain voltage amplifier types, this device included, the maximum permissible screen
grid input varies with the screen grid voltage, as shown in Figure 10.2. Full rated screen grid input
is permissible at screen grid voltages up to 50 percent of the maximum rated screen grid supply
voltage. From the 50 percent point to the full rated value of supply voltage, the screen grid input
must be decreased. The decrease in allowable screen grid input follows a curve of the parabolic
form. The rating chart is useful for applications utilizing either a fixed screen grid voltage or a
series screen grid voltage-dropping resistor; specifically:
•
When a fixed voltage is used, it is necessary only to determine that the screen grid input is
within the boundary of the operating area on the chart at the selected value of screen grid volt-
age to be used.
·
When a voltage dropping resistor is used, the minimum value of resistor that will assure tube
operation within the boundary of the curve can be determined by the relation
Where:
Pentode grid #1 to triode plate
0.2 pF max.
Pentode plate to triode plate
0.1 pF max.
Class A
1
Amplifier, Maximum Ratings (Design-Maximum Values)
Triode Unit
Pentode Unit
Plate voltage
330 V
330 V
Grid #2 (screen grid) voltage
Figure 10.2
Grid #2 (screen grid) supply voltage
330 V
Grid #1 (control grid) voltage, positive bias value
0 V
0 V
Plate dissipation
2.5 W
3 W
Grid #2 (screen grid) input
For grid # 2 voltages up to 165V
0.55 W
For grid #2 voltages between 165 and 330V
Figure 10.2
Characteristics
Plate supply voltage
125 V
125 V
Grid #2 (screen grid) supply voltage
110 V
Grid #1 (control grid) voltage
–1 V
–1 V
Amplification factor
40
—
Plate resistance (approx.).
—
200 k
Ω
Transconductance
7500 μmhos
5000 μmhos
Plate current
13.5 mA
9.5 mA
Grid #2 (screen grid) current
3.5 mA
Grid #1 voltage (approx.) for plate current of 20 μA
–9 V
–8 V
Table 10.1
Key Parameters of the 6U8A
(
)
2
2
2
2
2
c
cc
c
g
c
E
E
E
R
P
−
≥
Summary of Contents for JC Whitaker 20 W Stereo Integrated Audio Amplifier
Page 1: ...20 W Stereo Integrated Amplifier WhitakerAudio 20 W Stereo Integrated Audio Amplifier ...
Page 11: ...11 20 W Stereo Integrated Audio Amplifier Figure 1 1 b ...
Page 16: ...16 WhitakerAudio Figure 1 2 b ...
Page 20: ...20 WhitakerAudio Figure 1 3 Power management circuit for the 20 W integrated stereo amplifier ...
Page 38: ...38 WhitakerAudio Figure 3 1 Component layout for the Amplifier PWB 1 right board ...
Page 40: ...40 WhitakerAudio Figure 3 2 Rectifier PWB component layout ...
Page 45: ...45 20 W Stereo Integrated Audio Amplifier Figure 3 4 Layout of the speaker terminal PWB ...
Page 84: ...84 WhitakerAudio Figure 5 6 Power management PWB a component side b foil side a b ...
Page 188: ...20 W Stereo Integrated Amplifier WhitakerAudio 20 W Stereo Integrated Audio Amplifier ...
Page 196: ...196 WhitakerAudio ...
