RED HEAD - Dual Mono configured Stereo headphone amplifier

Output power: min. 0.5W (into 32 ohms)

Compatibility: min. 130mA RMS into 16-600 ohms

Tubes: per channel 6C5 (driver stage), 2x 7AK7 (output stage)

RED HEAD is a tube OTL (Output TransformerLess) amplifier based on our proprietary MT-OTL technology. The RED HEAD amplifier will drive lower impedance headphones, or two pairs of headphones using an external splitter.

* MT-OTL technology – a result of our own research and development, MT standing for ‘Mirror Triode’. It uses a hybrid element to provide a push-pull output configuration where an output triode is opposed to it’s own mirror image. However, unlike the classic push-pull, a triode and ‘anti triode’ opposed do not result in a combined element that suppresses even harmonics (an acceptable but not the most desirable characteristic of the classic push-pull topology. Rather, it results in a ‘double size’ triode. The end result is that of two parallel triodes in a SE (Single Ended) topology, retaining the natural distribution of harmonics that is one of the defining characteristics of SE. At the same time, the MT circuit insures proper operating conditions of the output triode in strict class A. The whole circuit does not require any adjustment nor matching tubes – and offers a significant reduction in power consumption and heat generation, to boot. The usable bandwidth of an MT-OTL amplifier easily exceeds that of any currently standard HD audio formats.

* Lifetime Warranty on output tubes – OTL amplifiers as a rule get labeled as ‘tube eaters’. Because of this we have chosen high reliability pentode tubes with multiple control options, which offer a multitude of possible configurations. Out of these, we chose a high linearity triode connection, which exceeds even the linearity of the legendary 300B tube, and also happens to be the most suitable for OTL operation. These tubes were made for the military and navy, and are specified for at least 10000 operating hours in the harshest conditions. Because of this, they found use in transoceanic telecommunication cable repeaters, where tubes are documented to have logged more than 100000 operating hours. We operate them very conservatively so they will last a lifetime.

* Two inputs with link function to other components – in case the amplifier is integrated into a larger system that shares sources, we provide two inputs and through (‘link’) connections to another amplifier. In this manner it is possible to use the headphone amplifier without having to switch on the rest of your system.

* Careful filtering and regulation of the power supply – even mediocre headphones will reproduce signals on the order of microvolts, while SE topologies (effectively the mode of operation of an MT-OTL amplifier) generally do not offer high levels of suppression of power supply noise and hum. This situation requires special effort to insure a high quality, stable and quiet power supply of the amplifier circuits. Both amplifiers feature multiple filtering, regulation using a low noise voltage reference and post-filtering of the power supply, for a stable power supply impedance and output voltage.

* Dual mono configuration – the RED HEAD amplifier is constructed as two independent mono amplifiers including the power supplies, with independent secondary windings on a common transformer. The resulting two mono amplifiers are connected together in a single point, the star ground of the input and phones connectors.