Mythical 300B tube
Invented in the laboratories of the Bell telephone company in 1938 for telephony applications, it enabled the development of more powerful relay transmitters to support the rapidly developing network.
The characteristics of this tube are proven without doubt and drew the attention of engineers in the cinema industry who, with the coming of sound to motion pictures, were looking to equip theatres with high quality sound installations. The innovation did not escape pioneering HiFi engineers either who, in turn, adopt it to create amplifiers until now unseen.
The 300B triode was such a good development that it remains, even today, an unbeatable component for building exceptional amplifiers. Its linearity, low distortion and natural harmonic response close to ideal leaves modern transistors in its wake.
Comfort and security
Although it was built around a historical component, the 300B triode, the Nagra 300p amplifier is by no means nostalgic or historical electronically. The approach was to surround the tubes with the most evolutionary technology possible so as to draw the maximum musical quintessence to offer a more global and comfortable use.
The 20 watts RMS power per channel achieved is generous, bearing in mind the type of tube being used. It drives all medium to high sensitivity loudspeakers, which are numerous in todays’ market. The biasing of the latter is easily done by the user, who benefits from the indications on the modulometer located on the front face of the amplifier. This instrument is also able to display the output power of the amplifier and the correct impedance matching between the amplifier and the loudspeakers, making connection to the connectors on the rear of the unit easier.
The 300p is equipped with a system ensuring the security of the circuits, preserving both the correct operation and life time of the tubes. A microprocessor controlled surveillance circuit manages the gentle power-up “soft start” of the units and monitors the internal electronics permanently.
Any anomalies are indicated by means of a LED on the front face.
The 300p power amplifier benefits from hybrid circuit topology allowing the 300B tubes to be perfectly exploited in a Class A push-pull mode.
End-to-end coherence, the circuits achieve such precision that no feedback correction is needed on the output: thus the stability is perfect and all load types can be driven without any risk of oscillation.
The care with which the power supply circuits were dimensioned, regulated and filtered also contributes to the exemplary performance while maintaining operation free from parasitic noise, or mains interference.
An extraordinary listening
With a bandwidth ranging from 14 Hz to 56 kHz and a signal-to-noise ratio exceeding 105 dB, the Nagra 300p has nothing to envy from the best transistor electronics available today.
The transparency and the neutrality are the first imposing qualities. The legendary musicality of the 300B triode takes a new dimension, with exquisite treble and mid-range. The soundstage offers a three dimensional and vibrant realism. The bass management at very low frequencies is also remarkable, out of the ordinary for a 300B tube stage.
Quality maintained with all types of 300B
Today, the 300B triodes are manufactured by several different companies of differing origins and are available at very affordable prices. Some users take pleasure in making comparative tests between the different types available, which could provoke undesired audio artefacts. The Nagra 300p lends itself well to such tube changes as its circuits always ensure a high performance in all configurations.
Transformers wound by hand
The in-house wound transformers used in the 300p are hand-made by Nagra, on specially built machines. This delicate operation, that few manufacturers in the world are able to perform, is critical as to the high performance of tube electronics, as the quality of the output transformers determines the overall global performance that can be achieved.
Protection of the mechanical integrity
The Nagra 300p is delivered with a double set of shock-absorbing plates Nagra VFS which contribute to the overall integrity of its operation.