Not just an replacement, but an improvement!

EML 520B-V2
and
 EML520B-V3

Last data sheet revision:
2011-Dec-02

Description

The 520B is a long plate Version of the older 52B, with many technical improvements added. The EML520B is a state of the art product, in the family of the 300B tubes. This powerful tube is recommended for new  designs. The 520B has the  same outside dimensions as the "845" tube, but longer 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.

Applications:

1) Use as large 300B tube.

Though this is no drop-in replacement for 300B, you will often be able to replace a 300B. Care needs to be taken to have the right bias, and also you need to make sure the filament voltage is 5 Volt. With some knowledge of electronics, you will find this tube a superb replacement for 300B tubes. One of the best things you get with the 520B is the lower plate resistance (480 Ohms of 520B vs 700 Ohms of the 300B). This will lead to higher efficiency, and a gain of output signal, even at the SAME bias settings. The lower plate impedance will give better control of the BASS speaker chassis, since the damping factor increases with 25% compared to standard 300B.

2) Use as large SE 300B alike tube.

The higher bias which is possible with this tube, will allow you to build 18....20Watt SE amplifiers.

3) Use as Push Pull tube.

The 520B-V3 is ideal for Push Pull applications, since the higher peak emission (vs 300B) will ensure much longer lifetime for the 520B, vs 300B. Occasional overload of a push pull stage is hard to prevent, of the user overdrives the amplifier. Other than a SE stage, the power dissipation of a Push Pull stage is quite dependant of the maximum output signal, and rises even sharply if you drive a PP stage into distortion. Unlike the previous models (called 52B), the 520B is not immediately taking damage if the tubes are used above maximum dissipation. Of course we can not specify how far you can exceed the maximum, but the thermal capacitance of the anode is very large, and this is the best protection against accidental (short time) overload. Another protection is the special grid, which will not develop grid current after occasional overload of the Push Pull stage. Last but not least we use a special anode composite, which allows very high dissipation.

Features

  • Double Mica tube top (Note6)
  • 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

 
Important
Read all notes at the bottom of this data sheet before installing this tube.
.
Filament Ratings (See note4 and 5) 
 
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 Note3.  

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) 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 4) Filament current has changed, from June 2005 to the value in this data sheet 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. 

    Note 5) When using a slow-start circuit for the filament, you may not apply plate voltage during that time.

    Note 6) 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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