Not just an replacement, but an improvement!

2A3-Mesh
2A3-Mesh-V4

Uploaded: 25.03.2017->

Description 

This tube is a plug & play, direct replacement for original the RCA 2A3 mono plate tube.   It features a mesh window in the plates.  This combines the electrical stability of solid plate tubes, with the non-resonance mesh material. We think this is the most ideal combination for a low power audio tube. 

Sound Character of the 2A3-mesh

When a tube is given mesh plates, something magic happens to the sound.  We believe this is caused by the high damping properties of the mesh material.  When using mesh tubes, you will experience what people call a more "transparent" sound stage, meaning a more realistic stereo reproduction of the original sound recording.  With this quality product you will enjoy the very best of what small triodes have to offer. 

The EML 2A3-Mesh  tube is constructed for lowest microphonics. All critical parts, like filaments and  grids  are made of hard metal for higher reliability and reproducible quality.  The tube base is now glued on the glass with anti-vibration rubber.

We have two versions for the heater: Normal heater, or Center Tapped heater.

With the center tap connected tubes, we enter a new field of applications. This has not been done before with Audio tubes. When biasing a DHT tube there is no cathode to connect something to. The cathode must be artificially constructed, by a resistor network. Since many years, all EML tubes already feature a center tapped heater, which is a way to enforce better electrical field geometry. Only, to this center tap there was never an electrical connection. So to the tube itself we had to make no changes. To the center tap of the heater, is now connected a wire, which becomes the third connection to the heater. Now the tube has five wire connections, and for this reason we can not use the 4 Pin UX4 base any more. We have chosen for the Octal base. It must be said, the V4 is a very special tube, which fulfills the needs of Circuit Design purists the best possible way. Depending on how you do it, you can enter new design fields, or you may choose to connect the center tapped tubes just the classical way. Even so, for tube testing you can ignore the center tap, and just connect the tube the regular (four pole) way. In that case, the EML1605-V4 will behave like a standard four pole tube. In the case you own center tapped tubes, but you whish to connect them like a non-center tapped tube, this is possible too. In that case just do not connect the center tap.

Here is a link to Application Note 06, describing the center tapped tubes in general. Link here.

Recommended transformers

Single Ended: LL1623-60mA (Wire secondary for ALT B, C, D for : 4, 8, 16 Ohms in this order)
Single Ended: LL1664-60mA (Secondary 8 Ohms)

Parallel Single Ended: LL1627-140mA (Wire secondary for ALT B, C, D for : 4, 8, 16 Ohms in this order)

Push Pull LL1620-PP (Wire secondary for ALT C, D, E for : 4, 8, 16 Ohms in this order)
Push Pull LL1620-PP-CFB (with optional 25% Cathode feedback winding)

Complete list of recommendations here

Features

  • Gold plated Grid (Note1)
  • Gray Wire Mesh
  • Soft rubber suspended tube base
  • Center tapped filament
  • Fully compatible to solid plate 2A3
  • Hard metal Construction (Note8)
  • 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.)


Type 2A3-Mesh 

High. Res.Images: 
Front - Side 
Gold Grid


EML 2A3-Mesh
Standard UX4 Base


EML 2A3-Mesh V4
Special Octal Base.
(see the main text)

Compatible to 6S4S
but 6S4S has 6.3V heater

2A3-Mesh  Filament Ratings
Filament Voltage 
= 2.5Volt (AC or DC) 
Tolerance on filament voltage
4%
Filament Current 
~ 2.5Ampere 
.
2A3-Mesh Maximum Conditions
Plate Voltage 
350Volt 
Plate Current 
70mA 
Plate Dissipation Continuous
17Watt 

Highest possible Grid to ground resistor, Single Ended.

250kOhm 

Highest possible Grid to ground resistor, Push-Pull.

50kOhm 
..
2A3-Mesh Factory Test conditions 
Plate Voltage 
250V 
Plate Current
60mA 
Grid Voltage
matched
Transconductance
matched
..

2) Typical application
Recommended operating point

All bias methods are possible

Plate Voltage 
250V 
Plate Dissipation 
15Watt 
Plate Current 
60mA 
Grid Voltage 
-45Volt 
Plate Impedance (Rp)
 800 Ohm 
Amplification Factor 
 4,1 
Transconductance (Gm)
5,2mA/V 
Load Impedance (Ra)
 2500 Ohm
Power Output @ Ra = 2500k
3.5 Watt  

..
2A3-Mesh Mechanical Data

Size including Socket
(but excluding pins)

147 x 60 mm

Weight of one tube:
140 Gram

Pin 1: Heater1
Pin 4: Heater2
Pin3: Anode (Plate)
Pin2: Grid

Standard UX4 Base

Size including Socket
(but excluding pins)
147 x 60 mm

Weight of one tube:
140 Gram

Pin 1+2: Heater1
Pin 6+7: Heater2
Pin 8: Center Tap (Cathode)
Pin3: Anode (Plate)
Pin5: Grid
Pin4: Not on tube base

Special Octal Base, V4 Version
Shipment weight for 
pair in gift box: 730 Gram
.
  • Note 1) Hard-metals can be used in electron tubes, though these are more difficult to use, and more costly than the classical nickel. Hard metal plates have a more precise plate distance, and do not change shape when heated, or at mechanical shock. This ensures reproducible tube parameters, and long term stability. Wolfram grids allow the most precise grid wire distance, because wolfram is an extreme hard metal. Best grid geometry ensures 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 is on the outside of the tube box. Each tube is numbered from the inside, with a metal Tag
  • Note 3) Plate Curves: Made with the Sofia Digital Curve tracer. Plate curves with courtesy of AMR
  • Note 4) We recommend the same values as Western Electric in their 1950 Data sheet.
  • Note 5) The Western Electric 1950 Data sheet. says 36 Watt maximum dissipation. Later data sheets say 40 Watt. Though 40 Watt is possible, this is a peak value only, and no normal working point. When you intent to get the "maximum" out of a 300B, and operate this tube at the limits of safe operation, it is a better idea to use the 300B-XLS in such a case.
  • Note 6. Some manufacturers claim to be the only one with a center tapped filament, but this is not longer true. At EML we build since several years now all triodes center tapped, not only the the 300B.
  • Note 7) Don't experiment with lower filament voltage, and expect better lifetime. If it was that easy, we would make them like this yourself. The specified filament voltage is the one for best lifetime.
  • Note 8) Gold plated grids have a few advantages. Amongst other this will give better bias stability of the tube, some protection against accidental overload, and better linearity of tube curves.

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