Not just an replacement, but an improvement!


EML 300B-2.5V

Released and ready to ship
Uploaded: 14-Okt-2018->->->-


Warning: This tube can not be used in a classical 300B amplifier. For testing with a tube tester, you need to use 2A3 settings

The 300B-2.5V is a direct replacement for the 2A3 tube. Users of 2A3 tubes have a limited choice of tubes to use. There was only 2A3 and 2A3-Mesh. With the 300B-2.5V we offer an alternative tube. The idea is to get a slightly different sound, and possible a small gain in output power for any amplifier.

Guarantee

The first owner can register the tube at the Emission Labs ®website, to participate in the 5 years guarantee program.

Some Background of this tube

It is interesting to see, electrical data of the 300B tube at the operating point of 2A3 is very similar, and apart from the heater voltage, a 300B could replace the 2A3. So we have put the heater of the 2A3 tube inside a 300B, to get a 300B tube with heater specifications of the 2A3. We call this tube 300B-2.5V.

300B-2.5V Filament Ratings
Filament Voltage 
2.5Volt (AC or DC) 
Tolerance on filament voltage
4%
Filament Current 
2.5Ampere 

Tube data: We refer to the 300B data sheet, which is valid for this tube, with the only exception of the heater voltage.

The following table is a excerpt of the Western Electric 300B Datasheet, for the Anode voltage of 250V only

Excerpt of Western Electric 300B Datasheet
 
Anode
Voltage

Control Grid Voltage

Anode
Current
Load
Resistance
Power
Output
2nd
Harmonic
Line2

250V

-48V

60mA
2000
4.7 Watt
26dB
Line3

250V

-48V
60mA
2700
4.1 Watt
30dB
.
Classical working point of the RCA 2A3 tube
 
Anode
Voltage

Control Grid Voltage

Anode
Current
Load
Resistance
Power
Output
2nd
Harmonic
Line1

250V

-45V
60mA

2500

3.5 Watt
26dB
.

It can be quickly seen from the 300B working points at 250V / 60mA / 2700 Ohms, that the output power is approximately 0.6 Watt higher, and the distortion is 4dB less. We have to say, this is so at 2700 Ohms load, whereas the RCA 2A3 working point is at 2500 Ohms load. So loading the 300B-2.5V with 2500 Ohms vs 2700 Ohms, will further increase the output power to an estimated 4.2 Watt, at the price of perhaps 1.5dB more distortion. Yet, this leaves us with distortion figures, better than 2A3 still, and output power higher than 2A3. This is the idea behind the 300B-2.5Volt.

Bias Voltage at 60mA: It can be seen from the above tables, bias of the 300B-2.5V differs 3 Volts from the 2A3. This is much within the natural tolerance of the 2A3. Though this was never officially specified, the bias voltage can well vary from -38V to -55V for some tubes.

Conclusion

If the increase in output power is indeed proven to work in any amplifier, we do not want to claim this here. It would mean improve such a great tube like RCA 2A3, simply by using the anode and the grid of the 300B. Yet, a compare of the electrical data as published by RCA and WE, does indicate this improvement clearly. From our side, we just would like to bring this tube under your attention as a possible and interesting replacement of the 2A3, with a sound character of it's own. It is expected to have slightly less distortion and slightly higher output power. We have to say also, we can not guarantee this to happen under all circumstances.

Some words about Distortion

In electronics, distortion can be expressed as percentage of the signal, or in dB. Using dB, is more related to human hearing, meaning a similar difference in dB, is experienced the same. This is why many technicians prefer dB. As as rule of thumb it can be said, a 3dB change can be heard by anyone, but below that needs a trained ear.

The 26dB rule of thumb: -26dB of 2nd harmonics is the level at which most human ears just do not hear this distortion. So at -25dB or more, you will experience this as minimal distortion. Whereas harmonics added with a levels of -20dB or more, sounds not pleasant any more.

Some examples of 2nd harmonic distortion level
Sterile Sound
-36dB or better
Triode Sound
-27dB or better
Some can hear this as distortion, some can not.
-26dB
Can heard by direct compare
-24dB
Can be heard always
-22dB
Not HiFi any more
-20dB

 


EML 300B-2.5V

Side - Top


Anode curves

Some customer feedback:

4.10.2018 / Krzysztof Leonarcik

Hello Jac, It has been 3 weeks since I got my new Emission Labs ®300B 2.5V. Anode version. From the very beginning it became obvious to me how good they are. It is not surprising that after 21 days they are even better. They deliver incredibly razor sharp three-dimensional images I have never ever got from my speakers. The realism of presentation, richness and beauty of the music, harmony, emotions, the thrill of the listening - all of them are top notch. Really addictive tubes. The best of all 300B/2A3 hybrids I have ever used in my amp. I am really looking forward to mesh Anode version. P.S. If you want, you can quote my feedback on your new and very nice page.


 


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