Not just an replacement, but an improvement!

This  very powerfull tube is recommended for new  520B designs.  The "V3"  is a +25%  "long plate" Version of the 520B, and it is the largest single plate DHT available today. It has the  same outside imensions as an 845, but larger plates. All critical parts, like filaments, grids and plates are constructed of hard metal for higher reliability and reproducable quality.  The only difference with the 520B-V2 is the filament voltage.

• Note the relation between tube base  size and plate size, and compare this with our 300B.    This hughe tube has the size of an 845.  It is the largest single plate DHT with oxide coated filaments, build today. 

• Ceramic socket with gold plated pins
• Hard metal filaments and Plates, Wolfram Grids (Note1)
• 0.5 mm thick plates
• 10 circular coolers (4 single + 6 double plates)
• Wolfram Grids (Note1)
• Two extra large getters, flashing the complete tube bottem. 
• Hand blown ST Glass bulb
• Anti-microphonic plate- and grid  suspension
• These tubes are shipped in a high quality dual box
• Tube pinting with real gold (metal),  red color is burned into the glass 
• Machined, solid tube base pins for highest contact precision. Ideal for the YAMAMOTO tube sockets. 
• Gold plated pins,  black ceramic socket.  (White bottem)

• Note 1)  Hard-metal filaments prevent filament breakage with DHT Tubes.  This material has a higher melting point than the classical nickel wires. Hard metal plates have a more precise plate distance, and do not change shape when heated.  This ensures  reproducable tube parameters, and long term stability. Wolfram grids  allow the most precise grid wire distance, because wolfram is an extreme hard metal.   This ensures better uniformity and linearity at the low end of the tube curves.

• Note 2)  Individual Test data, such as:  Matching Data, Grid Current, Vacuum, Filament Current, etc,  are on the Certificate that comes with each individual Tube.  Each tube  is numbered, inside the bulb  with a metal Tag
 
• Note 3)  Tube Curves:  The Sofia Curve tracer can handle max. 270mA plate current, so we couldn't use it for this tube.  The plates curves are measured  point by point up to a value 400mA, and entered in an Excel worksheet. 

• Note 4)  Maxmimum specifications. These data are only to show the safety distance to the recommended operationg point.   You can operate the tube at the maximum for a short period of time.  Exceeding the maximum, willdecrease the lifetime  very rapidly.  For long term reliability,  the tube should not  be operated  above  the "typical"  dissipation  (green table)