The 300B-mesh can replace a standard 300B in several cases, but not in all cases. So please read this data sheet carefully.

Do not simply plug & play a 300B-mesh instead of a 300B. Overheated anodes may result if you do not check the following conditions, and such a damage is not covered by the guarantee. The 300B mesh can replace a normal 300B tube, when you can meat following conditions:

1. Bias and Plate dissipation must be reduced from 22 Watt to absolute maximum 28 Watt. (see below table)
2. Filament current of minimum 1.4 Ampere can be supplied
3. The larger length of the tube is no problem. (like with closed amplifiers)

The 300B mesh is a "long plate" version, and the plates are 25% longer as with normal 300B we build. The physical size of this tube, inside and outside is the same as the larger 520B tubes we make, so it is much larger than you may expect from a 300B. Check the dimensions at the end of this Data sheet. The heat dissipation of the mesh wire is lower than for solid plate anodes. So the maximum plate dissipation of the 300B Mesh for continuous use must be limited to typical 22Watt, or absolutely maximum 28Watt. This is however a classical use condition in several Japanese products. Though many other amplifiers exceed this number, so it is important to check with your amplifier manufacturer first, if you are not sure about the plate dissipation.

Sound Character of the 300B-Mesh tube

Why Mesh plates? When a tube is given mesh plates, something magic happens to the sound! We believe this is caused by the better damping properties of the mesh material.  A solid plate anode due to it's circular construction will have quite some ringing (bell like effect). A mesh anode will not have this effect. In most cases, when using mesh tubes, you will experience a more transparent sound stage, meaning a more realistic stereo reproduction of the original sound recording. With mesh tubes you will enjoy the very best of what small triodes have to offer. 

Note: mesh means woven metal wire. Chinese factories make a tube with punched plates, and for marketing call this "mesh". A punched plate from solid metal will also have this ringing effect, and can never have the superior resonance damping properties a wire mesh tube has. 

• Gray Wire Mesh plates, mounted on a hard metal frame for best stability.
• Gold plated, Wolfram Grid
• Soft rubber suspended tube base
• Center tapped filament
• Slow Start filaments, for best lifetime
• 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.)

Grid resistor @ Plate Dissipation= 22 Watt

Grid Voltage

Plate Current (ma)

Plate Rp (Ohm)

Load 
(Ohm)

Plate Dissipation (Watt)

Power Output (Watt)

2nd harm.
(dB)

350

-73

63

720

2000

22

10.6

21

350

-73

63

720

3000

22

8.7

26

350

-73

63

720

4000

22

7.3

30

350

-72

70

685

3000

24

8.5

28

.

400

-74

60

720

3500

24

10.5

26

.

440

-101

59

775

4000

26

12

26

440

-101

59

775

5500

26

9.6

30

* For best lifetime, it is recommended to choose maximum 26 Watt Plate dissipation, though 28 Watt is possible at some compromise with life time. If you need higher output power than 300B-Mesh can do, choose standard 300B, or upgrade to 300B-XLS.

Choice of output transformer impedance: For each working point, a wide range of primary impedance is possible. When using a transformer of another value, you can estimate the output power and distortion by averaging between two rows of this table. Example: 450V, 60mA. Use of Lundahl LL1679-70mA (4k5 type). This will give you appr. 11.5 Watt @ 27dB 2nd harmonics. (28dB distance of signal to 2nd harmonics.

740 Gram 

• Note 1)  This tube has gold plated grids, and additional to this it has several other new features, that we do not to publish for competition reasons. The result of this is, if a tube like this gets accidental overheated, the risk on damage is greatly reduced, compared to classical tubes, and compared to tubes as we produced them before. As end-user you can recognize a tube of this series by the gold plated grid. The gold color of the grid is visible with the bare eye, when you look carefully. We do not say you can overheat this tube, but chances on damage are greatly reduced in case it would happen anyway by mistake.
• 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 has  is numbered, inside the bulb  with a metal Tag
• Note 3)  Plate Curves:  Made with the Sofia Digital Curve tracer.  Plate curves with courtesy of AMR