4CX350AC/8321A - 350 W Radial Beam Power Tetrode

Penta Labs 4CX350AC/8321A: Compact Powerhouse for Audio & RF Applications

The Penta Labs 4CX350AC/8321A is a high-performance, air-cooled tetrode vacuum tube designed for demanding audio and RF amplifier applications. This compact tube boasts a maximum plate dissipation of 350 watts, making it suitable for Class AB1 audio or RF amplifier service where robust performance and extended tube life are paramount.

The 4CX350A/8321A is a direct replacement for the 4CX350A, offering identical external dimensions and electrical characteristics, except for a marginally increased warm-up time. It features a ruggedized internal construction for superior reliability and longevity, while its increased amplification factor and cathode area compared to the 4CX250B translate to higher transconductance, contributing to peak performance.

Product Specifications

Maximum Plate Dissipation: 350 Watts

Maximum Screen Dissipation: 8 Watts

Maximum Grid Dissipation: 0 Watts

Frequency for Max Rating (CW): 110 MHz

Amplification Factor: 13

Filament/Cathode: Oxide Coated

Voltage: 6.0 Volts

Current: 2.9 Amps

Capacitance (Grounded Cathode):

• Input: 23.6 pF
• Output: 5.6 pF
• Feedthrough: 0.3 pF

Capacitance (Grounded Grid):

• Input: - pF (Not specified)
• Output: - pF (Not specified)
• Feedthrough: - pF (Not specified)

Cooling: Forced Air

Base: 9-Pin Special

Socket: SK-600A

Chimney: SK-606

Benefits:

High power output capability (350W) for demanding applications

Compact size for space-constrained designs

Ruggedized construction for extended tube life

Direct replacement for 4CX350A

Improved transconductance and figure of merit over 4CX250B

Ideal for:

• High-fidelity audio amplifiers
• RF power amplifiers
• Industrial and scientific applications requiring reliable high-power tubes