VACUUM TUBE DATA

Basic technical information on a few select audio tubes concerning pin-out, voltage ratings and general tube use.

You should never exceed the maximum voltage rating of a tube. However, remember that the maximum voltage is as measured across the tube, from plate to cathode.
Since there is usually a resistor is series with the plate or cathode, there will be a voltage drop across these resistors. Even with a 350 volt supply voltage, there may only be 200 volts across the tube.

Using the highest possible voltage, without exceeding the tube maximum rating, will yield the best tube performance. The higher the supply voltage the more voltage the tube can swing resulting in more audio headroom and less distortion.

NOTE: Where push-pull transformer primary load resistance is plate-to-plate, a 3000 ohm plate-to-plate transformer would be a 3000 ohm center tapped transformer. Each end of the winding goes to a plate and the center tap goes to the supply voltage.

6CA4

FULL WAVE RECTIFIER
1000V PLATE TO PLATE MAXIMUM
TYPICAL OPERATION
350V PLATE TO PLATE
OUTPUT DC VOLTAGE (350V P-P) APROX 490V
OUTPUT CURRENT 150MA
PIN 1 = PLATE 1
PIN 2 = NOT USED
PIN 3 = CATHODE
PIN 4 = FILAMENT 6.3V @ 1 AMP
PIN 5 = FILAMENT 6.3V @ 1 AMP
PIN 6 = NOT USED
PIN 7 = PLATE 2
PIN 8 = NOT USED
PIN 9 = NOT USED

6L6G

Power Output Tube
Good for 10 watts class A single stage output
Good for 45 watts dual push-pull class AB1
This tube requires a control grid negative bias supply
This tube may be operated in any position
This tube gets very hot, provide cooling
PIN 1 = NOT USED
PIN 2 = FILAMENT 6.3V @ .9 AMPS
PIN 3 = PLATE maximum plate voltage = 500VDC
PIN 4 = SCREEN GRID (#2) maximum screen voltage = 450VDC
PIN 5 = CONTROL GRID (#1)
PIN 6 = NOT USED
PIN 7 = FILAMENT 6.3V @ .9 AMPS
PIN 8 = CATHODE AND SUPPRESSOR (#3) GRID
~
APROX TYPICAL OPERATION
SINGLE TUBE
PLATE SUPPLY VOLTAGE = 350VDC
SCREEN GRID VOLTAGE = 250VDC
PLATE OUTPUT TRANSFORMER PRIMARY = 4200 ohms
PLATE CURRENT = 66ma
SCREEN GRID CURRENT = 7ma
CONTROL GRID RESISTOR = 100K ohms
CONTROL GRID BIAS SUPPLY = -18VDC
POWER OUTPUT = 10 WATTS
~
SINGLE TUBE TRIODE CONNECTION
(screen grid connected to plate)
PLATE SUPPLY VOLTAGE = 350VDC
PLATE OUTPUT TRANSFORMER PRIMARY = 5000 ohms
PLATE CURRENT = 60MA
CONTROL GRID RESISTOR = 100K
CONTROL GRID BIAS SUPPLY = -20VDC
POWER OUTPUT = 1.5 WATTS
~
DUAL TUBE PUSH-PULL
PLATE SUPPLY VOLTAGE = 360VDC
SCREEN GRID VOLTAGE = 270VDC
PLATE OUTPUT TRANSFORMER PRIMARY = 7600 ohms plate-to-plate
PLATE CURRENT = 205ma
SCREEN GRID CURRENT = 15
CONTROL GRID RESISTOR = 100K ohms
CONTROL GRID BIAS SUPPLY = -22.5VDC
POWER OUTPUT = 45 WATTS

12AT7 (ECC81)

Dual Triode low gain voltage amplifier tube
Tube may be used as low power output tube.
Ample power to drive headphones
Use output transformer with 10K primary rated 1 watt or higher
Does not require control grid bias supply
PIN 4 & 5 FILAMENT = 12.6V @ .15 AMPS (pin 9 not used)
PIN 4 & 5 CONNECTED TOGETHER and PIN 9 FILAMENT = 6.3V @ .3 AMPS
PIN 1 = PLATE (2) maximum plate voltage = 300VDC @ 15ma
PIN 2 = CONTROL GRID (2)
PIN 3 = CATHODE (2)
PIN 6 = PLATE (1) maximum plate voltage = 300VDC @ 15ma
PIN 7 = CONTROL GRID (1)
PIN 8 = CATHODE (1)
~
APROX TYPICAL OPERATION
PLATE SUPPLY VOLTAGE = 250VDC
PLATE OUTPUT TRANSFORMER PRIMARY = 10K ohms
or PLATE RESISTOR = 100K ohms
CATHODE RESISTOR = 1K ohms
PLATE CURRENT = 12ma
CONTROL GRID RESISTOR = 470K ohms
CONTROL GRID BIAS SUPPLY = NONE

12AU7 (ECC82)

Dual Triode medium gain voltage amplifier tube
Good tube for voltage amplifiers
Good tube for cathode follower output
Does not require control grid bias supply
PIN 4 & 5 FILAMENT = 12.6V @ .15 AMPS (pin 9 not used)
PIN 4 & 5 CONNECTED TOGETHER and PIN 9 FILAMENT = 6.3V @ .3 AMPS
PIN 1 = PLATE (2) maximum plate voltage = 300VDC @ 20ma
PIN 2 = CONTROL GRID (2)
PIN 3 = CATHODE (2)
PIN 6 = PLATE (1) maximum plate voltage = 300VDC @ 20ma
PIN 7 = CONTROL GRID (1)
PIN 8 = CATHODE (1)
~
APROX TYPICAL OPERATION
PLATE SUPPLY VOLTAGE = 350VDC
PLATE RESISTOR = 100K ohms
CATHODE RESISTOR = 1.2K ohms
PLATE CURRENT = 10ma
CONTROL GRID RESISTOR = 470K ohms
CONTROL GRID BIAS SUPPLY = NONE

12AX7 (ECC83

Dual Triode high gain voltage amplifier tube
Good tube for pre-amplifiers
Does not require control grid bias supply
PIN 4 & 5 FILAMENT = 12.6V @ .15 AMPS (pin 9 not used)
PIN 4 & 5 CONNECTED TOGETHER and PIN 9 FILAMENT = 6.3V @ .3 AMPS
PIN 1 = PLATE (2) maximum plate voltage = 330VDC @ 8ma
PIN 2 = CONTROL GRID (2)
PIN 3 = CATHODE (2)
PIN 6 = PLATE (1) maximum plate voltage = 330VDC @ 8ma
PIN 7 = CONTROL GRID (1)
PIN 8 = CATHODE (1)
~
APROX TYPICAL OPERATION
PLATE SUPPLY VOLTAGE = 300VDC
PLATE RESISTOR = 200K ohms
CATHODE RESISTOR = 1.5K ohms
PLATE CURRENT = 2.0ma
CONTROL GRID RESISTOR = 1M ohms
CONTROL GRID BIAS SUPPLY = NONE

12AY7

Dual triode medium gain voltage amplifier
Good tube for lower noise pre-amplifiers
Does not require control grid bias supply
PIN 4 & 5 FILAMENT = 12.6V @ .15 AMPS (pin 9 not used)
PIN 4 & 5 CONNECTED TOGETHER and PIN 9 FILAMENT = 6.3V @ .3 AMPS
PIN 1 = PLATE (2) maximum plate voltage = 300VDC @ 10ma
PIN 2 = CONTROL GRID (2)
PIN 3 = CATHODE (2)
PIN 6 = PLATE (1) maximum plate voltage = 300VDC @ 10ma
PIN 7 = CONTROL GRID (1)
PIN 8 = CATHODE (1)
~
APROX TYPICAL OPERATION
PLATE SUPPLY VOLTAGE = 300VDC
PLATE RESISTOR = 200K ohms
CATHODE RESISTOR = 1.5K ohms
PLATE CURRENT = 4.0ma
CONTROL GRID RESISTOR = 1M ohms
CONTROL GRID BIAS SUPPLY = NONE