Not just an replacement, but an improvement!

EML 520B-V2
and
 EML520B-V3

Last datasheet revision:
2008-March-20

Description

This  very powerful tube is recommended for new  designs. The older type 52B is not recommended any more for new designs. The 520B is a +25%  "long plate" Version of the 52B. The 520B has the  same outside dimensions as the "845" tube, but larger plates. All critical parts, like filaments, grids and plates are constructed of hard metal for higher reliability and reproducible quality.  Note the relation between the tube base, and and the glass bulb. Then compare this with our 300B.   This gives you some idea of this tube's size.

Features

  • Double Mica tube top (Note7)
  • Gold plated, Wolfram Grid
  • Soft rubber suspended tube base
  • Center tapped filament
  • Slow Start filaments, for best lifetime
  • 0.5 mm thick plates
  • 10 circular coolers (4 single + 6 double plates)
  • Hard metal Construction (Note1)
  • Two extra large getters
  • Hand blown Glass bulb
  • Anti-microphonic plate- and grid  suspension
  • These tubes are shipped in a high quality dual box
  • Tube printing with real gold (metal),  red color is glass burned into the glass 
  • Machined, solid tube base pins for highest contact precision. YAMAMOTO tube sockets highly recommended. 
  • Gold plated pins,  black ceramic socket.  (White bottom.)

520B-V2/V3
Detailed image
Plate Curves
Note3
 
Important
Read all notes at the bottom of this datasheet before installing this tube.
.
Filament Ratings (See note 5 and 6) 
 
520B-V2
520B-V3
Filament Voltage (AC or DC)
6.5 Volt
5.0 Volt
Tolerance on filament voltage
5%
5%
Filament Current
2 Ampere 
1,8 Ampere 
.
 
Maximum Conditions
(Not possible simultaneously) 
See also Note4.
Plate Voltage 
550Volt 
Plate Current 
200mA 
Power Output in Class A 
27Watt 
Grid resistor
max. 50kOhm 
..
 

Typical application
Recommended operating point
See also Note4.  

All bias methods are possible

Plate Voltage 
425V 
Plate Dissipation 
55Watt 
Plate Current 
130mA 
Grid Voltage 
-90Volt 
Plate Impedance (Rp)
 480Ohms 
Amplification Factor 
 4.0 
Transconductance (Gm)
8,3mA/V 
Power Output in Class A
18,3Watt 
Load Impedance (Ra)
 1000-2400Ohm 
Grid resistor
100kOhm 
. 
Mechanical Data 
 Size including Socket
(but excluding pins)

200 x 68 mm
7.5 x 2.7 Inch 

Single tube weight 
240 Grams 
Shipped weight 
for double box 
950 Grams 
.
 
    Note 1)  Hard metal has a higher melting point than classical nickel. Hard metal gives a more precise material shape, and does not change the shape when heated.  This ensures  reproducible tube parameters, and long term stability. Hard metals allow the most precise grid wire distance, and ensures better uniformity and linearity 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) This is a heavy power tube, and using it safely means avoid risks. The maximum conditions are destructive limits, which should not be reached even for a short moment. A "maximum possible" working point exists, but we do not specify it, because it is generally not a good idea to try this with any power device,both vacuum state or solid state, when you expect long life and reliability at the same time. We found that if we specify a "maximum" operating point, that in the end some users will try this out. So what we publish here, is the recommended working point, which gives best reliability, optimized sound and safe use at the same time.

    Note 5) Filament current has changed, from June 2005 to the value in this datasheet. For tubes of older date, please refer to the filament current value as written on the certificate that is in the original tube box. Please inquire when this data got lost. 

    Note6) When using a slow-start circuit for the filament, you may not apply plate voltage during that time.

    Note 7) Gold Grids is a word generally used for gold plated grids, so not gold wire grids. The grids we use are made of specially purified hard metal, which is then thermally gold plated. The advantage of gold plated grids is better temperature stability, and lower grid current if the tube gets very hot, and (within limits) it protects the tube from overheating damage and gives some self repairing effect after accidental overheating.

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