Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders.

---

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ Tube DIY Asylum ]

---

[ Alert Moderator ]

---

The problem

Posted by Paul Joppa (P) on April 11, 2014 at 14:18:54

In Reply to: ping deathtube 667 re: starved filaments posted by GSH on April 10, 2014 at 13:02:14:

I see nobody has posted this yet.

At normal filament voltage there is a substantial cloud of electrons surrounding the cathode. This "space charge" serves three useful functions:

1) It protects the cathode from ion bombardment (cathode poisoning), extending the life of the tube.

2) By forcing a more uniform net flow of electrons from different parts of the cathode surface, it reduces the noise generated. (This is used in so-called noise diodes, which run a current through a starved cathode to generate white noise efficiently.)

3) By forcing a more uniform net flow of electrons from different parts of the cathode surface, it prevents the formation of hot spots on the cathode, extending the life of the tube.

Starving the cathode reduces the space charge nearly to zero, as show by the high-current limited emission.

This post is made possible by the generous support of people like you and our sponsors:

Kimber Kable

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---