Van den Hul The Flexicon B4 Jack/RCA 1m

In 1990, South Africa’s BOP studios commissioned Van den Hul to equip their three 96‑channel SSL, Neve and Focusrite consoles, among the largest ever built. The Dutch manufacturer then developed the Flexicon B4, a balanced cable capable of ensuring reliable interconnections over 75 kilometers of runs. Since then, this model has been available to the general public and is now offered in a 3.5 mm mini‑jack to RCA version.

Origins in the professional studio world

The original Flexicon B4 brief was anything but trivial: it involved fully wiring one of the largest recording complexes in the world. BOP studios, located in Mahikeng in the former Bophuthatswana, housed three control rooms equipped with legendary consoles: an SSL 4000G+, a Neve VRP96 and one of the ten Focusrite Studio Consoles ever made. Within these walls, artists such as Ladysmith Black Mambazo, Miriam Makeba and even Disney’s The Lion King original soundtrack were recorded.

Van den Hul had to design a cable that met multiple, sometimes contradictory requirements: flawless transmission quality, low inter‑conductor capacitance to preserve signal clarity, effective shielding against surrounding interference, and above all sufficient flexibility to facilitate the dense wiring of 96‑channel consoles. The result convinced three of the biggest names in the professional audio industry at the time.

Silver‑plated OFC conductors with crystalline structure

The two conductors of the Flexicon B4 are 24 AWG, each made up of 12 strands with a diameter of 0.15 mm. The chosen material is large‑crystal oxygen‑free copper (OFC), coated with a dense layer of silver plating. This enlarged crystalline structure reduces the number of joints between metal grains, those micro‑discontinuities that can disturb electrical flow. Silver, whose electrical conductivity exceeds that of copper, optimizes signal transmission on the surface of the conductor—where high frequencies naturally travel due to the skin effect.

The resistance of the central conductors is 8.45 Ω per 100 meters, i.e. less than 0.085 Ω per meter. This value, combined with the small overall diameter of 0.52 mm per conductor, allows compact wiring without compromising transmission quality. The red and black color code of the two cores makes identification easier during installation or troubleshooting.

Double shielding and controlled capacitance

The inter‑conductor capacitance of the Flexicon B4 is limited to 47 pF per meter, a moderate value that preserves dynamics and signal definition over long distances. This performance stems from the polypropylene insulation surrounding each conductor: this material has a low dielectric constant and maintains excellent mechanical flexibility.

The shielding uses a two‑layer architecture. The first is a tight helical spiral of 48 strands of 0.12 mm, providing dense coverage and good flexibility. The second, a reinforced aluminum foil subjected to a specific treatment, completes the protection against electromagnetic and radio‑frequency interference. The resistance of this shield is 2.85 Ω per 100 meters, low enough to effectively drain parasitic currents that are picked up.

Hulliflex jacket and long‑term durability

The white outer jacket of the Flexicon B4 is made from Hulliflex, a polymer developed by Van den Hul as an alternative to conventional materials such as PVC. Since 1990, the Dutch manufacturer has gradually phased out halogen‑based insulators in its production, a move driven by environmental considerations—halogenated materials release harmful compounds such as hydrochloric acid or dioxins when burned or disposed of.

According to Van den Hul, Hulliflex offers three times the mechanical stability of PVC while retaining great flexibility. It resists chemical aggression, temperature variations and natural aging. The cable thus maintains its mechanical and electrical properties for many years, even in demanding environments such as automotive or permanent installations. The 3.7 mm outer diameter makes it easy to route through tight spaces.

Gold‑plated Van den Hul connectors

This Jack/RCA version of the Flexicon B4 comes pre‑fitted with Van den Hul connectors. The 3.5 mm stereo mini‑jack plug and the two male RCA plugs are gold‑plated, a treatment that prevents contact oxidation and ensures a stable long‑term connection. These in‑house connectors let you take full advantage of the cable’s qualities without requiring any assembly work or specific tools.

The mini‑jack to dual RCA configuration meets a common need: connecting a portable source, a computer, a tablet or any device with a headphone output to a hi‑fi amplifier, a pair of active speakers or a car audio system. The available length allows for flexible installation without putting excessive strain on the connectors.

Everyday use cases

The mini‑jack to RCA format fits into many home setups. A smartphone or digital audio player can feed an integrated amplifier, a network player with an auxiliary analog input or a pair of powered speakers. Owners of turntables with a built‑in phono preamp and mini‑jack output will also appreciate this connection to their main system.

In car audio, the cable’s low capacitance and effective shielding really come into their own: the electrical environment of a vehicle generates many disturbances likely to introduce hiss or interference into the audio signal. The Flexicon B4 isolates the music from these nuisances. Its flexibility makes it easy to route through trim panels and narrow conduits in the cabin.

Technical Specifications

Conductor construction

• Two 24 AWG conductors
  • 12 strands of 0.15 mm each
  • Total conductor diameter: 0.52 mm
• Material: large-crystal oxygen-free copper (OFC)
• Surface treatment: silver plating for optimal conductivity

Insulation and shielding

• Insulation: polypropylene providing maximum flexibility and minimal capacitance
• High-performance double shielding
  • Dense helical spiral: 48 strands of 0.12 mm
  • Reinforced treated aluminum foil
• Outer jacket: white Hulliflex ensuring longevity, resistance to aging, and flexibility

Electrical characteristics

• Capacitance: 47 pF/m between conductors for a pure signal
• Conductor resistance: 8.45 Ω/100 m (0.0845 Ω/m)
• Shield resistance: 2.85 Ω/100 m (0.0285 Ω/m)

Dimensions and finishes

• Outer diameter: 3.7 mm, ideal for compact internal wiring
• Jacket color: white

Available versions and connectors

• Cable type: balanced analog interconnect

Recommended applications

• Internal interconnects: preamplifiers, mixing consoles
• Audio / car Hi-Fi installations
• General-purpose interconnect wiring

Key features

• High-fidelity audio transmission thanks to silver-plated OFC conductors
• Very low capacitance ensuring clear, precise signals
• High flexibility for easy installation
• Exceptional durability provided by the Hulliflex jacket
• Double shielding offering excellent protection against interference