Matched Pairs of tubes are ordered directly from Emission Labs. Typical delivery is within 2-4 weeks.
This tube has the classical grid construction and the tube curves of the 300B. It has the stronger Anode construction and larger glass of the vintage 52B however. So in one tube we have combined the very best of two classical products.
Sound Character of the 300B-XLS tube
For use in Push Pull amplifiers, this is always the tube of choice, because this type of amplifier is hard on the tubes by definition. The 300B-XLS is made to deal with such conditions, and will allow the amplifier to play gently at low sound level, as well as reproduce higher sound level with the detail and precision you expect from a push pull amplifier.
For use in Single Ended amplifiers, the 300B-XLS is the best choice, since with those amplifiers good sound is coming from the right use of the tube, not over stressing the tube. The right use means, the tube should not be working at it's maximum electrical performance. Here we think the 300B-XLS is at it's right place, taking advantage of the higher electrical reserve this tube has. The 300B-XLS will reproduce the required loudness with more ease than the standard 300B. The result is a more transparent sound picture at low or medium volume, while at higher volume, the dynamics of the original recording will stay unaffected.
The 300B-XLS will bias in any amplifier the same way as the original WE300B. Sill it can be used in two ways if you want it. These two modes are explained here.
1) You can replace any 300B with this tube. Just plug it into any 300B amplifier, and the tube will set itself exactly to the original 300B working point. The EML 300B-XLS is is a very strong tube, and it will develop the output power with more ease. Specially for amplifiers that let the 300B tubes work very hard, the EML 300B-XLS is the right product to choose. Any amplifier that is trying to get as much as possible power out of a normal 300B, will benefit from the 300B-XLS. Improved sound and longer lifetime will be the result.
2) Another purpose of the EML 300B-XLS is to get more power, than is possible with standard 300B tubes. This can only be done when you have the possibility to adjust the settings of the amplifier. If you increase the Anode current of the tube ABOVE the standard 300B specifications, something very special will happen. The tube will now move to a part of the curves where it has a lower Anode resistance. This is a specialty of the 300B-XLS. This will give a better damping factor of the bass and mid range loudspeakers, resulting in a more natural sound. Check our customer feedback section of the website!
All critical parts, like filaments, grids and Anodes are constructed of hard metal for the best reliability and reproducible quality.
We have two versions for the heater: Normal heater, or Center Tapped heater.
With the center tapped 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.
Read More Here:http://www.emissionlabs.com/datasheets/EML300B-XLS.htm