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29 March 2017 


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807 Beam Tetrode

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General Information

The 807 valve is an indirectly heated beam tetrode designed for various uses including RF Amplifiers and Public address systems. The heater is made for operation in parallel with other valves in AC operated equipment.

The valve is a beam tetrode unit capable of an output of around 15 watts. It is a standard ST16 valve with anode connection to Top Cap ion a 5 pin base.

Characteristics

Cathode - indirectly heated
Heated voltage 6.3 V*
Heater current 0.9 A
Max. DC Heater to cathode potential 250 V
Max. Cathode current 125 mA

*The voltage should not vary more than 5% from the rated value if the valve is used under Class AB2 conditions or where the operating conditions are close to the maximum rating. Nor should it be more than 7% if used under Class A or AB1 conditions.

Dimensions

Maximum overall length 146mm
Maximum seated height 133mm
Maximum diameter 54mm
Net weight 71g

Mounting Position - Vertical

In extreme circumstances the valve may be run horizontally, then the plane of the major axis of the control grid & screen must be on a vertical plane. The plane will be correct if pin 3 is on the vertical diameter of the valve base.

Adequate ventilation should be considered when using this valve in equipment as it will become very hot in use.

807 Beam Tetrode mounting position diagram

BASE - American 5 pin (UX5)

Top Cap - American Miniature - CTI

CONNECTIONS

Pin 1          Heater
Pin 2          Grid 2
Pin 3          Control Grid 1
Pin 4          Cathode and Grid 3
Pin 5          Heater
Top Cap    Anode

Ratings

Tetrode Connection
Max anode voltage 600 V*
Max anode dissipation 300 V*
Max Grid 2 dissipation 25 W*
Max. Cathode current 3.5 W*
Max DC Grid current 5 mA*
Triode Connection (Anode and Grid 2 Strapped) †
Max Anode voltage 400 V
Max Anode Dissipation 25 W
Max signal DC Anode Current    

† In order to avoid parasitic oscillation the anode and pin 2 should be connected together through a 100 ohm resistance or an RF choke of approximately 20 microhenries.

* These ratings are absolute and must be reduced under certain specified conditions referred to later I this report.

Frequency Ratings

The ratings given in the above paragraphs apply to frequencies up to 60 Mc/s. Above this frequescy the maximum anode voltage and anode dissipation must be reduced in the correct proportion. So at 80 Mc/s they are reduced by 80% and at 120 Mc/s to 50% of the values specified. The valve is not normally satisfactory for operation at frequencies higher than this.

Inter-electrode Capacitances (approx)

Anode to Grid 1 0.2 pF
Grid 1 to Cathode    
G3, G2 Heaters 12.5 pF
Anode to Cathode 3.5  
G3, G2 Heaters 8.5 pF
Heaters to Cathode 10.0 pF

Typical Operation at Audio Frequencies

General Recommendations

As the high slope of this valve may cause parasitic oscillation it is advised than a100ohm resistor should be directly wired in series to the anode and directly connected to the top cap. This resistance should be around 47ohms when used in Class AB2 operation. If necessary a series grid resistor can be used directly wired to the grid contact of the valve holder but the effect on the frequency response should be taken into consideration before choosing the value of resistance. The resistance should not exceed 100,000ohms for class A operation and never used for Class AB2 operation.

The input coupling arrangement should be made in such a way as to avoid excessive resistance being introduced into the grid circuit. The resistance should not exceed 100,000ohms; however in Class A operation under automatic bias  conditions the value may be as high as 500,000ohms where essential.

Class 'A' Amplifier (Single Ended)

Triode Connection (Pin 2 and top cap strapped)
Heater voltage   6.3 6.3 V
Anode Voltage      250 250 V
Grid Voltage   -20 - V
Autobias resistor - 500 Ω  
Anode current (no signal) 40 40 mA  
Anode Impedance   1700 - Ω
Amplification factor   8 -  
Mutual Conductance   4.7 - mA/V
Anode load Impedance       5000 6000 Ω
Peak AF Grid Voltage   20 20 V
Total Harmonic Distortion 4.5 4.0 %  
Power Output       1.3 1.1 W

The curves shown below display power output, harmonic distortion and input signal voltage for fixed bias and autobias.

Graph showing valve type 807 triode connection class X amplifier power output and distortion versus A.F. input voltage
Graph showing valve type 807 triode connection class A amplifier power output and distortion versus A.F. input voltage

Class 'A' Amplifier (Push-Pull)

Triode Connection (Pin 2 and top cap strapped)

Values are for 2 valves.

         
           
Anode Voltage 250 250 325 325 V
Grid Voltage -20 - -30 - V
Autobias resistor - 250 - 375 Ω
Anode Current (no signal) 80 80 80 80 mA

Output load Impedance

         
(anode to anode) 5000 5000 8000 8000 Ω  
Peak AF Grid Voltage 40 40 60 60 V
Total Harmonic distortion 0.35 0.4 0.7 0.6 %
Power Output 3.5 3.1 5.75 6.0 W

The curves shown below display power output, harmonic distortion and input signal voltage for fixed bias and autobias of 250V HT and 325V HT.

Graph showing valve type 807 triode connection push-pull class 'A' amplifier power output and distortion versus A.F. input voltage
Second graph showing valve type 807 triode connection push-pull class 'A' amplifier power output and distortion versus A.F. input voltage
Third graph showing valve type 807 triode connection push-pull class 'A' amplifier power output and distortion versus A.F. input voltage
Graph showing valve type 807 triode connection class A amplifier power output and distortion versus A.F. input voltage

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Class 'A' Amplifier (Single Ended)

Tetrode Connection
Anode Voltage 250 250 350 500 500 V
Screen Voltage 250 250 250 200 200 V*
Grid Voltage -14 - -18 -14.5 - V
Autobias Resistor - 170 - - 280 Ω
Anode Current 72 75 54 50 50 mA
Screen Current 5.0 5.4 2.5 1.6 1.6 mA
Anode Impedance 22,500 - 33,000 38,500 - Ω
Mutual Conductance 6.0 - 5.2 5.7 - mA/V
Anode load Impedance 2500 2500 4200 6000 6000 Ω
Peak AF Grid Voltage 14 16 18 14.5 15.5 V
Total Harmonic distortion 10 10 15 11.6 13.6 %
Power Output     6.5 6.5 10.8 11.5 11.0 W

* When the anode volts are greater than the screen volts, a potentiometer should be used between the HT and chassis bypassing to AF signals rather than a series resistor.

The curves shown below display power output, harmonic distortion and input signal voltage for 250V fixed bias and autobias.

Graph showing valve type 807 class 'A' amplifier power output, distortion, screen current and plate current versus A.F. input voltage
Second graph showing valve type 807 class 'A' amplifier power output, distortion, screen current and plate current versus A.F. input voltage

Class 'A' Amplifier (Single Ended)

Values are for 2 valves

Tetrode Connection
Anode Voltage 250 270 270 500 500 600 600 V
Screen Voltage 250 270 270 300 300 300 300 V
Grid Voltage -16 -17.5 - -27 - -29.5 - V
Autobias Resistor - - 125 - 270 - 360 Ω
Peak AF Grid-Grid Voltage 32 35 40 54 72 59 81 V
Anode current (no signal) 120 134 134 100 100 80 80 mA
Anode current (max. signal) 140 155 145 154 119 150 97 mA
Screen Current (no Signal) 10 11 11 2.5 2.5 1.5 1.5 mA
Screen Current (max. Signal) 16 17 17 20 16.5 17.5 17.5 mA

Output load Impedance

               
Anode to anode 5000 5000 5000 8000 9000 10,000 10,000 Ω
Total Harmonic distortion 2 2 4 2.6 2.7 2.2 4.1 %
Power Output 14.5 17.5 18.5 38 32.5 47.5 36.5 W

The curves shown below display power output, harmonic distortion and input signal voltage for fixed bias and autobias.

Graph showing valve type 807 push-pull class 'AB' amplifier power output, distortion, screen current and plate current versus A.F. input voltage
Second graph showing valve type 807 push-pull class 'AB' amplifier power output, distortion, screen current and plate current versus A.F. input voltage
Third graph showing valve type 807 push-pull class 'AB' amplifier power output, distortion, screen current and plate current versus A.F. input voltage
Fourth graph showing valve type 807 push-pull class 'AB' amplifier power output, distortion, screen current and plate current versus A.F. input voltage

Class 'ABI' Amplifier (Push-Pull)

Values are for 2 valves.

Triode Connection (Pin 2 and top cap strapped)
Anode Voltage 400 V*
Grid Voltage -45 V
Anode Current (no signal) 60 mA
Anode Current (max. signal) 140 mA
Output load Impedance (anode to anode) 3000 Ω
Peak AF Grid to Grid Voltage 90 V
Total Harmonic distortion 3 %
Power Output 15 W

*If any variations are made it must be noted that the maximum ratings must not be exceeded.

The curves shown below display power output, distortion and input signal.

Graph showing valve type 807 triode connection push-pull class 'AB' amplifier power output, distortion and plate current versus A.F. input voltage

Class 'ABI' Amplifier (Push-Pull)

Values are for 2 valves.

Tetrode Connection
Anode Voltage 360 360 V
Screen Voltage 270 270 V
Grid Voltage -22.5 - V
Autobias resistor - 250 Ω
Anode current (no signal) 88 88 mA
Anode current (max. signal) 138 100 mA
Screen Current (no Signal) 5 5 mA
Screen Current (max. Signal) 16 19 mA

Output load Impedance

     
Anode to anode 6600 9000 Ω
Peak AF Grid to Grid Voltage 45 57 V
Total Harmonic distortion 1.8 4.0 %
Power Output 26.5 24 W

The curves shown below display power output, distortion and input signal voltage.

Graph showing valve type 807 push-pull class 'AB' amplifier power output, distortion, screen current and plate current versus A.F. input voltage

Class 'AB2' Amplifier (Push-Pull)

Values are for 2 valves.

Tetrode Connections

Maximum Ratings

           
Anode Voltage 600 V        
Screen Voltage    300 V        
Signal DC Anode Current 120 mA        
Signal Anode Input Power 60 W        
Signal Screen Input Power 3.5 W        
Anode Dissipation 25 W        

Typical Operating Conditions

           
Anode Voltage 360 360 400 500 600 V
Screen Voltage 225 270 300 300 300 V
Grid Voltage -18 -22.5 -25 -29 -30 V
Anode current (no signal) 78 88 90 72 60 mA
Anode current (max. signal) 162 220 240 240 200 mA
Screen Current (no Signal) 3.5 5 5 5 5 mA
Screen Current (max. Signal) 21 35 23 22 21 mA

Output load Impedance

           
Anode to anode 6000 3800 3200 4240 6400 Ω
Peak Grid to Grid Input Power 190 400 200 200 100 mW
Total Harmonic distortion 8 10 4 4.5 3.5 %
Power Output     31 47 55 75 80 W

The Anode and screen voltages must be within 5% and constant and the grid bias at 3% between no signal and max. signal. The driver stage should be capable of supplying the grids of the 2 valves with the specified peak voltages with low distortion.  The transformer or driver valve grid circuit should not have a greater resistance than 500Ω and the impedance or leakage inductance should not be greater than 700Ω.

The curves shown below display power output, distortion and input signal voltage.

Fifth graph showing valve type 807 push-pull class 'AB' amplifier power output, distortion, screen current and plate current versus A.F. input voltage
Sixth graph showing valve type 807 push-pull class 'AB' amplifier power output, distortion, screen current and plate current versus A.F. input voltage
Seventh graph showing valve type 807 push-pull class 'AB' amplifier power output, distortion, screen current and plate current versus A.F. input voltage
Eighth graph showing valve type 807 push-pull class 'AB' amplifier power output, distortion, screen current and plate current versus A.F. input voltage

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