Tube-Specific Calculators

Plate & Grid Circuit Calculator

12AX7/ECC83 High-Mu Dual Triode

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

The amplification factor, plate resistance, and transconductance are shown here based on the DC grid bias voltage. 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 100, plate resistance of 62.5k, and transconductance of 1.6mA/V, respectively, which are the approximations usually used by amplifier designers.

12AX7 AC characteristic curves

Example 1
Plate Voltage:	100 volts
Grid Voltage:	-1 volts
Plate Current:	0.5 mA
Plate Resistance:	80k ohms
Transconductance:	1.25 mA/V
Amplification Factor:	100

Example 2
Plate Voltage:	250 volts
Grid Voltage:	-2 volts
Plate Current:	1.2 mA
Plate Resistance:	62.5k ohms
Transconductance:	1.6 mA/V
Amplification Factor:	100

DC Operating Point Plate Voltage:
300 volts (325 volts for the 12AX7-A)

DC Peak Plate Voltage:
550 volts

DC Plate Current:
8 milliamps

Average Plate Dissipation:
1 watt (1.25 watts for the 12AX7-A)

Grid-to-Cathode Resistance:
2.2 megohms (22 megohms with cathode bias)

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

Positive DC grid voltage:
0 volts

Negative DC grid voltage:
-50 volts (-55 volts for the 12AX7-A)

Grid to Cathode+Heater: 1.6pF (no shield) 1.8pF (with shield)

Grid to Plate: 1.7pF

Plate to Cathode+Heater:
Left Triode: 0.46pF (no shield) 1.9pF (with shield)
Right Triode: 0.34pF (no shield) 1.9pF (with shield)

Equivalent Noise and Hum Voltage Referenced to Grid: 1.8 microvolts RMS

Measured in "True RMS" units under the following conditions:
Heater volts = 6.3 AC
center-tap of heater transformer connected to ground
plate supply volts (DC) = 250
plate load resistor = 100k
cathode resistor = 2.7k
cathode bypass capacitor = 100 microfarads
amplifier frequency range = 25Hz to 10kHz

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

Midrange Voltage Gain: 31
(measured at 2 volts RMS output)

Output Voltage: 5.0 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 2

Midrange Voltage Gain: 38
(measured at 2 volts RMS output)

Output Voltage: 6.9 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 3

Midrange Voltage Gain: 43
(measured at 2 volts RMS output)

Output Voltage: 6.5 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 4

Midrange Voltage Gain: 49
(measured at 2 volts RMS output)

Output Voltage: 8.6 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 5

Midrange Voltage Gain: 50
(measured at 2 volts RMS output)

Output Voltage: 7.4 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 6

Midrange Voltage Gain: 53
(measured at 2 volts RMS output)

Output Voltage: 9.1 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 7

Midrange Voltage Gain: 37
(measured at 2 volts RMS output)

Output Voltage: 3.9 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 8

Midrange Voltage Gain: 44
(measured at 2 volts RMS output)

Output Voltage: 5.4 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 9

Midrange Voltage Gain: 44
(measured at 2 volts RMS output)

Output Voltage: 5.0 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 10

Midrange Voltage Gain: 49
(measured at 2 volts RMS output)

Output Voltage: 6.4 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 11

Midrange Voltage Gain: 40
(measured at 2 volts RMS output)

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

Example 12

Midrange Voltage Gain: 46
(measured at 2 volts RMS output)

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

Example 13

Midrange Voltage Gain: 54
(measured at 2 volts RMS output)

Output Voltage: 18 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 14

Midrange Voltage Gain: 59
(measured at 2 volts RMS output)

Output Voltage: 24 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 15

Midrange Voltage Gain: 62
(measured at 2 volts RMS output)

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

Example 16

Midrange Voltage Gain: 64
(measured at 2 volts RMS output)

Output Voltage: 24 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 17

Midrange Voltage Gain: 53
(measured at 2 volts RMS output)

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

Example 18

Midrange Voltage Gain: 60
(measured at 2 volts RMS output)

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

Example 19

Midrange Voltage Gain: 61
(measured at 2 volts RMS output)

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

Example 20

Midrange Voltage Gain: 66
(measured at 2 volts RMS output)

Output Voltage: 21 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 21

Midrange Voltage Gain: 43
(measured at 2 volts RMS output)

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

Example 22

Midrange Voltage Gain: 50
(measured at 2 volts RMS output)

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

Example 23

Midrange Voltage Gain: 58
(measured at 2 volts RMS output)

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

Example 24

Midrange Voltage Gain: 64
(measured at 2 volts RMS output)

Output Voltage: 47 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 25

Midrange Voltage Gain: 66
(measured at 2 volts RMS output)

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

Example 26

Midrange Voltage Gain: 69
(measured at 2 volts RMS output)

Output Voltage: 46 volts RMS
(maximum output for 5 percent total harmonic distortion)

Example 27

Midrange Voltage Gain: 62
(measured at 2 volts RMS output)

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

Example 28

Midrange Voltage Gain: 67
(measured at 2 volts RMS output)

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

Example 29

Midrange Voltage Gain: 69
(measured at 2 volts RMS output)

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

Example 30

Midrange Voltage Gain: 71
(measured at 2 volts RMS output)

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

12AX7 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.

12AX7 base diagram