Data set 01
1937 Osram Valves
Published operating points and test conditions from this source.
SECTION 1
Triode
Other
Optimum load resistance
3200 ohm
Published operating data
Power - Triode ·Triode
PX25
Classic directly heated low-impedance audio power triode for high-quality Class A output stages. Approximately 25 W plate dissipation, high transconductance, and low plate resistance support roughly five watts of single-ended output.
Directly heatedCold cathodeCommon cathodeDissimilar
- Sections
- 1
- Base
- UX4
- Socket code
- B4
- Base pins
- 4
- Nominal heater
- 4 V / 2 A
Description
Classic directly heated PX25 audio output triode. The supplied Emission Labs sheet was read for filament data, maximum ratings, representative operating points, gm/rp/mu, output conditions, capacitances, and rectifier filter conditions as applicable.
Socket description
European 4-pin base
General specifications
Tube and section characteristics
Properties common to every published source and operating point.
Heater and base
- Base
- UX4
- Socket code
- B4
- Base pins
- 4
- Nominal heater voltage
- 4 V
- Nominal heater current
- 2 A
- Parallel heater voltage
- -
- Parallel heater current
- -
- Series capable
- No
UX4 - Terminal pinout
Electrical assignments shared by every tube using this base designation.
No verified pinout is recorded for this base designation.
Section ratings
1 physical section, each with unique specifications.
Section 1
Triode
X-ray radiationInterelectrode capacitances
- Plate resistance
- 1265 Ω
- Transconductance
- 0.0075 S
- Amplification factor
- 9.5
- Max plate voltage
- 400 V
- Max plate dissipation
- 25 W
- Max cathode current
- 90 mA
Published maximum ratings and characteristics audited; remaining useful numerical data retained in parameter table.
Source-dependent data
Operating conditions by source
Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.
Data set 02
193X Osram
Published operating points and test conditions from this source.
SECTION 1
Triode
Other
Heater/Filament Voltage
4 V
Published datasheet value
Heater/Filament Current
2 A
Published datasheet value
Maximum Anode Voltage
400 V
Published datasheet value
Maximum Anode Dissipation
25 W
Published datasheet value
Characteristics
Plate Resistance
1265 ohm
Published datasheet value
Mutual Conductance
8000 µS
Published datasheet value
Amplification Factor
9.5
Published datasheet value
Data set 03
1955 Marconi
Published operating points and test conditions from this source.
SECTION 1
Triode
Other
Published value [1]
2 A
2‘\ FILAMENT CURRENT 2-0 AMPS.
Published value [2]
2 A
2‘\ FILAMENT CURRENT 2-0 AMPS.
Published value [3]
0 mA
2‘\ FILAMENT CURRENT 2-0 AMPS.
ANODE VOLTS S0
0
ANODE VOLTS S00MAX. .
Ar £ [1]
4100 ohm
Ar £4100. £6O Marconi PX25 is a low impedance
Ar £ [2]
6 ohm
Ar £4100. £6O Marconi PX25 is a low impedance
Ar £ [3]
5 ohm
Ar £4100. £6O Marconi PX25 is a low impedance
< J| ‘_’"{;,‘,‘ffif,‘,’,‘,’?,”,‘fi:”””' triode giving }bout
5
< J| ‘_’"{;,‘,‘ffif,‘,’,‘,’?,”,‘fi:”””' triode giving }bout 5 watts output in
A ] T H [1]
4000 ohm
A ] T H 4000 ohms, bias resistance 475 ohms,
A ] T H [2]
475 ohm
A ] T H 4000 ohms, bias resistance 475 ohms,
Published value [1]
1
1 7 T grid bias 30 volts.
Published value [2]
7
1 7 T grid bias 30 volts.
Published value [3]
30
1 7 T grid bias 30 volts.
VRN = il AULANENT CURRENT [1]
20 A
: VRN = il AULANENT CURRENT 20of | efficiency pentode giving 10
VRN = il AULANENT CURRENT [2]
10 A
: VRN = il AULANENT CURRENT 20of | efficiency pentode giving 10
S grid bias of only
16
S grid bias of only 16 volts,
bias resistance
240 ohm
bias resistance 240 ohms,
screen current
12.5 mA
screen current 12.5 mA,
Data set 04
2026 Emission Labs
Published operating points and test conditions from this source.
SECTION 1
Triode
Characteristics
Filament voltage
4 V
Filament current
2 A
Plate resistance
1265 ohm
ClassA
Amplification factor
9.1
ClassA
Transconductance
7600 uS
ClassA
Other
Plate voltage
400 V
ClassA
Plate current
62.5 mA
ClassA
Grid voltage
-29 V
ClassA
Load resistance
3200 ohm
ClassA
Output power
6 W
ClassA