Tube-Specific Calculators

Plate & Grid Circuit Calculator

12AU7 Medium-Mu Dual Triode

RL & RT
RK
AC
Max Ratings
Capacitance
Vpp=90
Vpp=180
Vpp=300
Mechanical

The amplification factor, plate resistance, and transconductance are shown here based on the DC plate current. The various curves are for different values of DC plate voltage, which is indicated as E_b. The red, blue, and green lines represent an amplification factor of 17, plate resistance of 7.7k, and transconductance of 2.2mA/V, respectively, which are the approximations usually used by amplifier designers.

12AU7 AC characteristic curves

Plate Voltage:	250 volts
Grid Voltage:	-8.5 volts
Plate Current:	10.5 mA
Plate Resistance:	7.7k
Transconductance:	2.2 mA/V
Amplification Factor:	17
Cutoff Grid Voltage:	-24 volts

DC Operating Point Plate Voltage:
300 volts

DC Cathode Current:
20 milliamps

Average Plate Dissipation:
2.75 watts

Heater-to-Cathode Voltage:
200 volts (heater negative with respect to cathode)
100 volts (heater positive with respect to cathode, DC)
200 volts (heater positive with respect to cathode, DC+peak)

Grid Circuit Resistance:
250k (fixed bias)
1M (cathode bias)

Grid to Cathode+Heater:
1.8pF (with shield)
1.6pF (without shield)

Grid to Plate: 1.5pF

Plate to Cathode+Heater (left triode):
2.0pF (with shield)
0.4pF (without shield)

Plate to Cathode+Heater (right triode):
2.0pF (with shield)
0.32pF (without shield)

Capacitor values depend on the desired bass frequency response and can be computed using the Coupling Capacitor Calculator and Cathode Bypass Capacitor Calculator. Treble response can be computed using the Grid-Stopper Resistor Calculator.

Example 1-1

Midrange Voltage Gain: 10
(measured at 2 volts RMS output)

Output Voltage: 10 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 1-2

Midrange Voltage Gain: 11
(measured at 2 volts RMS output)

Output Voltage: 14 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 1-3

Midrange Voltage Gain: 11
(measured at 2 volts RMS output)

Output Voltage: 13 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 1-4

Midrange Voltage Gain: 11
(measured at 2 volts RMS output)

Output Voltage: 17 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 1-5

Midrange Voltage Gain: 11
(measured at 2 volts RMS output)

Output Voltage: 15 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 1-6

Midrange Voltage Gain: 11
(measured at 2 volts RMS output)

Output Voltage: 19 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 1-7

Midrange Voltage Gain: 14
(measured at 2 volts RMS output)

Output Voltage: 12 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 1-8

Midrange Voltage Gain: 14
(measured at 2 volts RMS output)

Output Voltage: 16 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 1-9

Midrange Voltage Gain: 14
(measured at 2 volts RMS output)

Output Voltage: 15 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 1-10

Midrange Voltage Gain: 14
(measured at 2 volts RMS output)

Output Voltage: 19 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 2-1

Midrange Voltage Gain: 11
(measured at 2 volts RMS output)

Output Voltage: 20 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 2-2

Midrange Voltage Gain: 12
(measured at 2 volts RMS output)

Output Voltage: 27 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 2-3

Midrange Voltage Gain: 11
(measured at 2 volts RMS output)

Output Voltage: 25 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 2-4

Midrange Voltage Gain: 12
(measured at 2 volts RMS output)

Output Voltage: 32 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 2-5

Midrange Voltage Gain: 12
(measured at 2 volts RMS output)

Output Voltage: 39 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 2-6

Midrange Voltage Gain: 12
(measured at 2 volts RMS output)

Output Voltage: 37 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 2-7

Midrange Voltage Gain: 16
(measured at 2 volts RMS output)

Output Voltage: 20 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 2-8

Midrange Voltage Gain: 16
(measured at 2 volts RMS output)

Output Voltage: 28 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 2-9

Midrange Voltage Gain: 15
(measured at 2 volts RMS output)

Output Voltage: 26 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 2-10

Midrange Voltage Gain: 16
(measured at 2 volts RMS output)

Output Voltage: 35 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 3-1

Midrange Voltage Gain: 11
(measured at 2 volts RMS output)

Output Voltage: 30 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 3-2

Midrange Voltage Gain: 12
(measured at 2 volts RMS output)

Output Voltage: 41 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 3-3

Midrange Voltage Gain: 12
(measured at 2 volts RMS output)

Output Voltage: 38 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 3-4

Midrange Voltage Gain: 12
(measured at 2 volts RMS output)

Output Voltage: 48 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 3-5

Midrange Voltage Gain: 12
(measured at 2 volts RMS output)

Output Voltage: 43 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 3-6

Midrange Voltage Gain: 12
(measured at 2 volts RMS output)

Output Voltage: 54 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 3-7

Midrange Voltage Gain: 17
(measured at 2 volts RMS output)

Output Voltage: 28 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 3-8

Midrange Voltage Gain: 17
(measured at 2 volts RMS output)

Output Voltage: 40 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 3-9

Midrange Voltage Gain: 16
(measured at 2 volts RMS output)

Output Voltage: 38 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 3-10

Midrange Voltage Gain: 16
(measured at 2 volts RMS output)

Output Voltage: 52 volts RMS
(maximum output for 5 percent total harmonic distortion)

12AU7 physical dimensions

Heater Requirements

Pin 4 to Pin 5:
12.6 volts
150 milliamps

Pin 9 to Pins 4 and 5:
6.3 volts
150 milliamps each leg

The tube can be mounted in any position.

12AU7 base diagram