Emission Labs 12B Driver/Output Rør - 1 Parret Par

Description
The 12B tube is in the family of 20A, 20B, 30B. It can be used as a medium gain driver tube, or as an output tube for smaller amplifiers, as well as head phone applications. With the appropriate circuitry (see application note) it can also be used as a line output tube.

Guarantee program for first owner
The first owner can register the tube within 4 weeks after receival, at the Emission Labs ® website, to participate in the 5 years guarantee program, which is additional to the legal obligations of the seller.

Features
Very wide Anode Distance for a nice glow picture.
Excellent linearity combined with medium gain.

Sound Character of the EML 12B
At smaller signal level, tubes with low gain often develop a sterile sound. Such tubes are not designed for small signal. Better is to use higher gain tubes for small signal, and medium gain tubes as a driver. As a rule of thumb, a tube like 300B requires 60 Volt AC signal on the grid. The gain of the 12B is a factor 12 to 14.5 depending on the load. If choke loaded, the gain will be 14.5. If speaker loaded, the gain will be around 12 to 13.

As a driver tube for 300B, the 12B would typically be operated choke loaded, or transformer loaded, and requires appr 4V AC signal on the grid. This can be achieved conveniently with a step up input transformer with a factor 1 : 3, resulting in an input sensitivity of 1.3 Volt. In this way, there is no more need for a pre amplifier tube, which would be only a source for hum and noise, because signal would be very low. Whereas an input transformer can supply a gain of factor 2...4 cost effective, and virtualy no noise or microphonics, and even prevents cable hum to enter the amplifier via the input.

In case even higher input sensitivity is needed, the 12B can also drive an inter stage transformer with a step up factor of 1:2 with ease.

The lower output resistance makes this tube uncritical in the choice of output transformers, yet keeping the gain around 12....14 depending on the application. This higher gain will develop the typical sound, of tubes like PX25 or RE604, which have a silky and non dominant sound.

A very nice application is also in a head phone amplifier, because relatively low output signal is needed, yet at lowest possible hum, noise and microphonics. Here, the use principle is another. Such amplifiers should be designed for having more amplification as strictly needed, and then the signal level is attenuated on purpose at the output. This attenuation will also attenuate any noise from the tube, making the amplifier very low noise. Yet, even at low signal on the head phone, still the output signal on the 12B is not extremely low, allowing the triode sound to develop.

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