power triodes (2,5Volt and 5Volt types) 300B, WE300B, 2A3, 320B, 300B XLS, AA32B, AA30B, AV300B Unless otherwise specified, these are matched in-house at BTB with an anode voltage of 350 volts
WE300B quad, directly heated power triode, UX4 base, 5V/1.2A heaterMatched quad, 72h burn-in selected and paired in the USA, wooden boxFor high-end stereo SET, dual mono and push-pull 300B amp projectsMu 3.85, gm 5.5mA/V, Rp 700 ohms, 450V / 40W max, dia 61mm, h 140mm
Delivery time: ca. 1 - 5 days
300BEH Gold - 300 B EH Gold - 300B EH Gold - Electro HarmonixUX-4 Pin ceramic Goldpin baseThe Upgrade of the 300B EHXvery recommend for OEMs - please send your RFQheight:140mm-socket diameter:36mm-bulb diameter:61mm (info can vary!)
Delivery time: ca. 1 - 5 days
Electro-Harmonix 300B Gold DHT triode, UX4, directly heated, 5 VFactory-matched pair for stereo SET and compatible 300B amplifiersGold grid wire is specified for improved bias stability by the makerEach valve draws 1.11.4 A; verify filament voltage and bias in use
Delivery time: ca. 1 - 5 days
height:140mm-socket diameter:37mm-bulb diameter:62mm (info can variy!)best Replica of the legendary Western Electric WE300B from USAthese meet harmonic, musicality and tone very close to the Originals
Delivery time: ca. 1 - 5 days
height:140mm-socket diameter:37mm-bulb diameter:62mm (info can variy!)best Replica of the legendary Western Electric WE300B from USAthese meet harmonic, musicality and tone very close to the Originalssince 2019 an upgrade to WE300B PSVANE (parameters and materials)
Delivery time: ca. 1 - 3 days
300BEH - 300 B EH - 300B EH - Electro HarmonixUX-4 Pin ceramic Goldpin basevery good price to quality rateThe best Choice for 300B startersheight:140mm-socket diameter:36mm-bulb diameter:61mm (info can variy!)
Delivery time: ca. 1 - 5 days
300B Electro-Harmonix Premium Matched Pair affordable hi-fiDirect heated, robust, musical and value priced for 300B ampsFor Fezz Mira Ceti 300B, Willsenton R300 Plus and DIY SET ampsUX4 4-pin, Uf 5V / If 1.25A, Pa 40W, S 5.5mA/V, Ri 700R, mu 3.85
Delivery time: ca. 1 - 5 days
300B Genalex GoldLion (PX300B) - 300 B Genalex - 300BGenalex300 BGenalex - 300 b Genalex - 300b Genalex - 300bGenalexUX-4 Pin white ceramic base, GoldpinsThe TOP 300B from Reflector Russiaheight:138mm-socket diameter:36mm-bulb diameter:61mm (info can variy!)
Delivery time: ca. 1 - 5 days
PX300B Genalex Gold Lion Premium Matched Pair hi-fi triodeAffordable high-end tube, dynamic, refined and musical for 300BFor Fezz Lybra 300B, Cayin HA-300MK2 and Line Magnetic 508IAUX4 4-pin, Uf 5V / If 1.2A, 40Watts, S 5.5mA/V, Ri 700R, mu 3.85
Delivery time: ca. 1 - 5 days
300B Genalex GoldLion (PX300B) - 300 B Genalex - 300BGenalex300 BGenalex - 300 b Genalex - 300b Genalex - 300bGenalexUX-4 Pin white ceramic base, GoldpinsThe TOP 300B from Reflector Russiaheight:138mm-socket diameter:36mm-bulb diameter:61mm (info can variy!)
Delivery time: ca. 1 - 5 days
UX-4 Pin tube-valve-baseAudio-HiFi-300B big Room, Response and Time, tendence warm toneheight:135mm-socket diameter:35mm-bulb diameter:61mm (info can variy!)
Delivery time: ca. 1 - 5 days
UX-4 Pin tube-valve-baseAudio-HiFi-300B big Room, Response and Time, tendence warm toneheight:135mm-socket diameter:35mm-bulb diameter:61mm (info can variy!)
Delivery time: ca. 4 - 8 weeks
UX-4 Pin tube-valve-baseheight:135mm-socket diameter:35mm-bulb diameter:62mmvery good mids, tight highs, tendence warm tonevery reliable type, this type was developed in the 1980´s
Currently sold out
UX-4 Pin tube-valve-baseheight:135mm-socket diameter:35mm-bulb diameter:62mmvery good mids, tight highs, tendence warm tonevery reliable type, this type was developed in the 1980´s
Currently sold out
height:135mm-socket diameter:35mm-bulb diameter:62mm (info can variy!)UX-4 Pin tube-valve-base
Delivery upon request
UX-4 Pin white ceramic Goldpin base
Delivery upon request
UX-4 Pin white ceramic base, GoldpinsMesh Plate, Globe Shape (Aubergine Shape)beautiful triode sound, nice mids and highsheight:146mm-socket diameter:36mm-bulb diameter:68mm (info can variy!)
Currently sold out
UX-4 Pin white ceramic base, GoldpinsGlobe Shape (Aubergine Shape)beautiful triode sound, nice mids and highsheight:150mm-socket diameter:37mm-bulb diameter:68mm (info can variy!)
Currently sold out
UX-4 Pin tube-valve-baseAudio-HiFi-300Bn good Room, fast Response and Timeheight:143mm-socket diameter:35mm-bulb diameter:65mm (info can variy!)
Delivery time: ca. 1 - 3 days
UX-4 Pin tube-valve-baseAudio-HiFi-PSVane-300Bn-300B/n good Room, fast Response and Timeheight:143mm-socket diameter:35mm-bulb diameter:65mm (info can variy!)
Delivery time: ca. 1 - 5 days
=300B/C but higher Anode Dissipation, close to 300BXLSUX-4 Pin white ceramic base, Goldpinsheight:179mm-socket diameter:35mm-bulb diameter:64mm (info can variy!)
Currently sold out
UX-4 Pin basebest price to quality rate in the marketcoke bottle/dome shapeheight:131mm-socket diameter:36mm-bulb diameter:51mm (info can variy!)
Delivery time: ca. 1 - 5 days
2A3 Sovtek Premium Matched Pair audio triode for hi-fi SETDirect heated, affordable, robust and musical for 2A3 ampsFor Bottlehead Stereomour II, Elekit TU-8900 and DIY 2A3 ampsUX4 4-pin, Uf 2.5V / If 2.5A, 131x51mm, Pa 15W, Ua max. 250V
Delivery time: ca. 1 - 3 days
UX-4 Pin base2,5V Version of the 300B JJPa=40Watt, Uf=2,5V, If=2,5Aheight:151mm-socket diameter:35mm-bulb diameter:63mm (info can variy!)
Delivery time: ca. 1 - 5 days
Power Triodes 300B / 300BXLS / 320B / 520B / 2A3 – Selection, Matching, and Use in Audio Applications
What are output tubes and power triodes?
Output tubes are power tubes that generate the actual output power in an amplifier’s output stage and drive the loudspeaker, usually via an output transformer. Power triodes are output tubes with a triode structure (one control grid) and are used in audiophile power amplifiers with lower output power (typically < 15 watts in single-ended operation).
Types such as 300B, 300BXLS, 320B, 520B, and 2A3 belong to the classic power triodes, but they differ significantly in electrical parameters, socket/pin configuration, heater requirements, and permissible dissipation. Therefore, choosing the correct type is essential for safe operation and reliable results.
What are the differences between 300B, WE300B, 300BXLS, 320B, 520B, and 2A3?
300B, 300BXLS, 320B, 520B, and 2A3 (as well as PX4, PX25, 45, 801, RS241, RS242, AD1) are different power triodes from related tube families, each with its own operating data and permissible working ranges. They are not interchangeable because heater voltage/current, maximum plate dissipation, characteristic curves, and often the recommended load impedance differ.
The 300B is a classic reference tube in single-ended hi-fi amplifiers and is often operated at practical plate voltages of around 350–400 V. The designation WE300B comes from the manufacturer Western Electric, which originally developed this tube. Today’s WE300B tubes (such as current US-made models, RSD, or Linlai) generally follow the internal structure of the original design. 300BXLS, 320B, and 520B are, depending on the version, considered higher-capacity or more robust variants in a similar format, but they still require an appropriate circuit design (bias, plate voltage, output transformer, and power-supply reserves). The 2A3 is also a classic power triode, typically operating in different heater and power ranges and often used in single-ended concepts with its own dedicated dimensioning. For repair and replacement, always check the schematic, datasheet, and the existing operating points instead of installing “similar” types.
How do I choose the right power triode for my amplifier?
The right power triode is the one that exactly matches the tube type specified for the circuit and operates within the defined parameters. Selection is based on the type specified by the device (e.g., 300B or 2A3), heater data, bias range, actual plate voltage, and the design of the output transformer and power supply.
If you plan to develop and build equipment using these power triodes, you should consider budget, sonic goals, availability and second-source options, driver stage requirements, and target output power.
What does “matched” mean, and which selections are available?
“Matched” means tubes are selected based on measurable parameters (e.g., plate current and transconductance at a defined operating point) so they closely track each other within tight tolerances. This reduces channel imbalance, minimizes differences in hum/distortion, and simplifies bias setup, while significantly improving spatial precision in particular for amplifiers without global negative feedback.
Power triodes in the 300B, 300BXLS, 320B, 520B, and 2A3 families are available as singles or as a matched pair, and sometimes as a matched quad; other selections are available on request. Unless stated otherwise, the tubes are matched in-house at BTB at practical plate voltages, i.e., under conditions close to real amplifier operation. For service shops and repair businesses, this matters because it reduces replacement rates and speeds up commissioning.
Can I swap a 300B for a 2A3 or for 300BXLS/320B/520B?
No: these tubes are not interchangeable, even if the form factor or application looks similar. Substitution without adapting the heater supply, bias, plate voltage, socket wiring, and transformer loading can lead to malfunction, overload, or damage.
For repair and replacement: if an amplifier is designed for 300B, the replacement should again be a 300B or WE300B, or an alternative explicitly approved by the manufacturer that is electrically and thermally compatible. Variants such as 300BXLS, 320B, or 520B may require different margins or operating ranges, and the circuit must support that. With the 2A3, the likelihood of mismatched heater and power requirements is especially high. For OEM and development applications, a clear type-family strategy (BOM, approvals, measurement protocols) is recommended to keep availability across Germany/Europe and international delivery predictable.
What are typical applications?
Typical applications for mid-power triodes are primarily single-ended, but also push-pull output stages in high-end audio, rarely studio applications, and very rarely certain guitar amplifier concepts (300BH). The choice of tube type influences achievable power, distortion behavior, dynamics, and the demands on the power supply and output transformer.
In hi-fi, 300B, WE300B, and 2A3 concepts are often appreciated for outstanding sound quality and a highly engaging musical presentation.