OTL Power Amplifiers
No output transformer
Till today Aitos uses tubes in the signal path as the best sounding and reliable way to amplify tiny electrical signals. Theory, but also our listening panel told us that a well built Output Transformer Less (OTL) amplifier is able to approach the live sound more accurately than any other amplifier, transistor or tube. Our OTL amplifiers give a sense of musical rightness, together with a realism that reveals the unique qualities of each recording. The midrange is light-filled and vivid, the highs are delicate and precise, the bass is rhythmic and propulsive and this together leads the ear brain system into thinking this is live music!
To understand why OTL is the better solution, we have to explain the theory and practice of ‘conventional’ tube amplifiers where a transformer is used in the signal path. In those amplifiers an output transformer is needed to transform a high voltage with a low current into a secondary lower voltage with a high current to match the low impedance of the loudspeakers. The output transformer has to have on the one side enough volume (much iron) to reproduce low bass, but on the other side also has to have as little volume as possible to reproduce high frequencies adequately. This contradiction is always a compromise in a ‘normal’ tube amplifier, with subsequent impact on the musical reproduction.
Furthermore output transformers have other drawbacks like phase distortion, lower slew rate, bandwidth restrictions and less dynamics because of saturation of the transformer core. Even the best possible transformer cannot avoid those problems.
The best output transformer is no transformer!
Extreme bandwidth
No transformer means no sound deterioration due to the presence of a transformer in between the output tubes and the loudspeaker and this also makes an extreme bandwidth and high rise time possible. This extreme bandwidth facilitates a perfect impulse response and prevents intermodulation products entering the audible spectrum.
AC power supply
To realise the potentially large dynamics of an OTL amplifier a large AC power supply of the best quality is imperative. This AC power supply, consists of an over-dimensioned transformer in conjunction with two huge capacitors with a large capacity. One has to accept that the power amplifiers consequently become a “weighty” device.
Three-dimensionally hard-wired
The EV 803 and the EV 903 are three-dimensionally hard-wired and fully handcrafted power amplifiers, while no printed circuit boards are used within the audio path. This is very beneficial especially for tube power amplifiers with their high temperatures, voltages and currents and thus enabling a long and reliable service (in any case more than 30 years!) that is unique in the market today.
Hand picked components
Each amplifier has hand-picked components to realise the ultimate in sound quality, neutrality and reliability. Some essential parts are manufactured according to AITOS specifications, e.g. the foil of the electrolytic capacitors is manufactured in a proven traditional process. These specially made capacitors are optimally suited for audio applications and have a very long service life. Comparable capacitors of this quality are rarely applied in amplifiers of other high-end brands, mainly due to the very high manufacturing costs.
Till today Aitos uses tubes in the signal path as the best sounding and reliable way to amplify tiny electrical signals. Theory, but also our listening panel told us that a well built Output Transformer Less (OTL) amplifier is able to approach the live sound more accurately than any other amplifier, transistor or tube. Our OTL amplifiers give a sense of musical rightness, together with a realism that reveals the unique qualities of each recording. The midrange is light-filled and vivid, the highs are delicate and precise, the bass is rhythmic and propulsive and this together leads the ear brain system into thinking this is live music!
To understand why OTL is the better solution, we have to explain the theory and practice of ‘conventional’ tube amplifiers where a transformer is used in the signal path. In those amplifiers an output transformer is needed to transform a high voltage with a low current into a secondary lower voltage with a high current to match the low impedance of the loudspeakers. The output transformer has to have on the one side enough volume (much iron) to reproduce low bass, but on the other side also has to have as little volume as possible to reproduce high frequencies adequately. This contradiction is always a compromise in a ‘normal’ tube amplifier, with subsequent impact on the musical reproduction.
Furthermore output transformers have other drawbacks like phase distortion, lower slew rate, bandwidth restrictions and less dynamics because of saturation of the transformer core. Even the best possible transformer cannot avoid those problems.
The best output transformer is no transformer!
Extreme bandwidth
No transformer means no sound deterioration due to the presence of a transformer in between the output tubes and the loudspeaker and this also makes an extreme bandwidth and high rise time possible. This extreme bandwidth facilitates a perfect impulse response and prevents intermodulation products entering the audible spectrum.
AC power supply
To realise the potentially large dynamics of an OTL amplifier a large AC power supply of the best quality is imperative. This AC power supply, consists of an over-dimensioned transformer in conjunction with two huge capacitors with a large capacity. One has to accept that the power amplifiers consequently become a “weighty” device.
Three-dimensionally hard-wired
The EV 803 and the EV 903 are three-dimensionally hard-wired and fully handcrafted power amplifiers, while no printed circuit boards are used within the audio path. This is very beneficial especially for tube power amplifiers with their high temperatures, voltages and currents and thus enabling a long and reliable service (in any case more than 30 years!) that is unique in the market today.
Hand picked components
Each amplifier has hand-picked components to realise the ultimate in sound quality, neutrality and reliability. Some essential parts are manufactured according to AITOS specifications, e.g. the foil of the electrolytic capacitors is manufactured in a proven traditional process. These specially made capacitors are optimally suited for audio applications and have a very long service life. Comparable capacitors of this quality are rarely applied in amplifiers of other high-end brands, mainly due to the very high manufacturing costs.
