The Russian audiophile 4P1L (4П1Л) is a directly heated power pentode with low anode voltage operation. The pentode is fine up to 100 Mc/s. Made by the Svetlana plant. Equivalent to the 4L1S / 4LS1. Copy of RL2 / 4P6 Wehrmacht tubes. It is a New Old Stock (NOS) item, never used, and is prized for its ability to deliver a rich, detailed sound signature that rivals classic directly heated triodes when wired in triode mode.

Key Features & Specifications

• Name: 4P1L
• Type: pentode
• Application: oscillation and power amplification up to 100 MHz
• Cathode type: oxide, direct heating
• Envelope: glass
• Mass: 35 g
• Filament voltage: 2.1 V / 4.2 V
• Filament current: 0.65 A / 0.325 A
• Anode voltage: 150 V
• Anode current: 0.06 A
• Anode power: 7.5 W
• Grid 2 voltage: 150 V
• Grid 3 voltage: 0 V
• Steepness: 4.5–7.8 mA/V
• Microphonic noise: 500 mV
• Socket type: rsh7

Applications & Compatibility

• Primary use: output stage in single-ended (SE) and push-pull audio amplifiers, as well as a driver or preamp tube in high-fidelity designs.
• HF capability: designed for oscillation and power amplification up to 100 MHz, making it suitable for vintage radio transmitters and RF equipment.
• Triode mode: when wired as a triode, the 4P1L exhibits superb linearity and can deliver up to 2.5 W per valve, often outperforming classic triodes in terms of linearity.

Condition

• Status: NOS (New Old Stock). Never used.
• Origin: Made in the USSR by the Svetlana plant (St. Petersburg).

Why Choose This Tube?

The 4P1L is a hidden gem of the tube audio world. As a directly heated pentode, it offers the immediacy and tonal purity that only DHT designs can provide, yet it does so at a fraction of the cost of famous Western triodes. When triode-strapped, its linearity is so exceptional that it has become a benchmark among DIY audio enthusiasts, capable of delivering a beautifully open and dynamic sound. Beyond audio, its 100 MHz rating and rugged Soviet construction make it a capable RF oscillator and transmitter tube, echoing its lineage as a copy of the legendary Wehrmacht RL2 / 4P6. Whether you are building a purist single-ended amplifier or restoring vintage radio equipment, the 4P1L delivers authentic DHT magic and Soviet reliability in one compact envelope.