The constant pursuit of purer and more authentic sound drives innovation in the audio world. In this context, I am excited to introduce the 23i3 filament choke, a 45mH component designed to revolutionize the stabilization of filament power supplies in directly heated tubes.
When designing a passive stabilization for filament supplies, the choice of a reactance coil emerges as an option that can significantly reduce residual AC noise, sometimes even surpassing the performance of series IC regulators.
No matter how precisely you build an IC regulator circuit, the residual (white) noise level is inevitably higher than that of coil-based solutions. After witnessing this in practice, your perspective on electronic IC regulators will likely change dramatically.
Engineered for Sonic Excellence
Originally conceived for the 101D tube, the 23i3 choke was designed to deliver a clean and stable current supply to tube filaments. With a 45mH inductance, it can handle up to 1A of filament current, making it versatile and suitable for a wide range of tubes with similar requirements. Although initially developed for the 101D, the 23i3 can be used with any directly heated tube requiring up to 1A of filament current.
Advantages of Coil Technology
The 23i3 choke offers several advantages derived from coil-based technology. Compared to IC regulators and traditional electronic circuits, a choke significantly reduces residual AC noise, resulting in a cleaner and interference-free sound experience. One of its defining traits is the ability to deliver cleaner power to the tubes, ensuring a more detailed and transparent audio signal — a quality highly valued by demanding audiophiles.
In the reference illustration, I implemented a specific configuration for the 101D tube, aiming to provide a filament supply that mimics, as closely as possible, the reliability and purity of battery power. I chose to create an RCLC cell, with the final capacitor being a 5-Farad, 5-Volt supercapacitor. This configuration proves highly effective in reducing ripple compared to similar approaches such as CRC filtering with a supercapacitor.
The resistor placed immediately after the rectifier bridge can have a very low value, such as 0.47 ohm. It acts as a damping element, helping to mitigate rectification noise during circuit operation. Moreover, the 5-Farad supercapacitor’s charge time constant allows a soft start for the filament, reducing mechanical stress and extending the tube’s lifespan. This circuit solution dissipates very little heat, unlike IC stabilizers, which often require heat sinks.
Technical data
Inductance: 45mH
Operating current: 1A
Saturation current: 1.4A
RDC: 400 milliohm
Conclusions
In conclusion, the 23i3 filament choke (45mH) represents a step forward in audio innovation, designed to meet the needs of the most demanding audiophiles. With its ability to deliver clean and stable energy to directly heated tubes, it stands out as an excellent choice for those seeking the highest sound quality. Experience the future of sound with the 23i3 choke and discover a new dimension of audio performance. Custom chokes can also be made on request for tubes such as the 2A3, 300B, and others. If you’re interested, please contact me through the contact form.