Since 1993, HALCRO'S research and development has been centered around creating the perfect amplified sound
Reference is a term used far too loosely in the high-end audio world. Most companies name a line of products 'reference quality'. To be truly reference quality a product must show it can reproduce music exactly as it was recorded. Un-colored and with bass that has not been enhanced, in other words, straight wire with gain! Quite simply this is not the case with most products. Halcro amplifiers at full power produce a level of purity of better than 99.9995% across the entire audio range; as close to perfection as you can reasonably expect. Halcro has reduced the levels of total harmonic distortion (THD) at full power up to 20kHz to less than 500 parts per billion. (THD specifications of our typical best competitors are 200,000 parts per billion.) Such a massive improvement in technology clearly requires a new description to differentiate it from conventional technology. We call this new art "Super-Fidelity" technology , rather than "high fidelity."
As a result, when listening to the HALCRO amplifiers, you will notice that the character and beauty of the instruments and vocals are retained, and there is no valve-added sound, no transistor-added sound, just the original music quite untarnished by the electronics. To quote respected audio reviewer and writer, Mr Dan Sweeney when writing about the effect that is created by HALCRO'S distortion specifications, he says "Like a higher magnification factor, if that makes any sense. Details within a recording that are buried with other amplifiers are exhumed with the Halcro.
Instrumental timbres sound truer and more immediate, not hyped or larger than life, just sonically right. Dynamics are excellent as well, with no sense of stress at any listening level and no change in sonic character accompanying level changes". - Dan Sweeney, The Absolute Sound , issue 121, Dec/Jan 2000. Quoted with permission.
The lower distortion amplifiers rely upon overall negative feedback to partially compensate for substantial deficiencies in the individual electronic stages making up the amplifier. It is well recognized in the industry that this technique of having intrinsically unpleasant high distortion levels within the amplifier, then feeding back a partially distorted signal from the output all the way to the input, is not satisfactory. Each stage of a HALCRO amplifier, has extremely low distortion in itself and has ideal stage characteristics (e.g. input and output impedance's, gain/phase transfer) to reduce the distortion due to the connections between stages to infinitesimal levels. In most amplifiers, the worst stage for producing distortion is the final output stage. A typical FET output stage produces a distortion of about 1% at high output powers.
The output stage of a HALCRO amplifier produces less distortion than any competitor's entire amplifier complete with negative feedback. The HALCRO amplifiers have been designed to drive all loudspeakers, including electrostatics. The output is also short circuit proof.
The following explanation will help your understanding of the importance of the degrading effect that distortion has on the listening experience.
Distortion is the appearance of new signals, or ghost notes, that are quite absent from the original recording. For example, when two notes are played simultaneously, say E in one octave and C in the octave above, the distortion of an amplifier will create a third note, G, in the octave below that of E.
In harmonically simple music with only a few instruments playing, distortion is sometimes not too objectionable. However, in harmonically complex music, such as orchestral music, distortion produces sounds, harsh to the human ear, by creating a myriad of inharmonic notes and exaggerating the harmonics of all the instruments. This effect increases with volume. Over the years, listeners have become accustomed to the inaccurate reproduction of amplified sound. You now have the opportunity to listen to your favorite music in its original and perfect state, as it was intended to sound at the time of recording. You will hear layers of musical tones that you have never heard before, even in recordings you know very well. You will be impressed by the sound stage produced by the HALCRO amplifiers, as it is second to none.
What is the technological fidelity limit?
The old limit was the amount of distortion generated by the power output transistors or valves, which remained even after overall negative feedback was applied.
In our revolutionary new system, the distortion in the output stage is so well corrected that the new limit of HALCRO is reduced to the performance of the most basic building block - the resistors. In other words, how well do resistors obey Ohm's law.
So while previous technology relied on negative feedback to minimize the effects of distortion, our dual correction system practically eliminates distortion within the output stage. The HALCRO solution of having ultra-low distortion inherent in all stages avoids the traditional problems of the 'overall negative feedback solution' such as distortion being fed back to input, and the inherent limitations of the lag through the whole amplifier.
The result is an amplifier of such outstanding potential that conventional technological terms fall short of adequately describing it.
Whilst most electronic architectures follow a few similar structures and are limited by transistors and valves, which are the weakest link in the fidelity chain, HALCRO genuinely challenges the strongest link in the chain - the basic fidelity limit.
The culmination of several technological developments that make this quantum leap possible is something we simply call Super Fidelity Amplification.
Input Stage: This stage is a low noise ultra low distortion voltage to current converter, which produces a particularly pure current even at high frequencies. A separate, well screened compartment virtually eliminates both electric and magnetic interference, in particular, any non-linear fields from the power output stage.
Intermediate Stage: Super-low distortion current to voltage converter.
Output from this stage is particularly divorced from the influence of the output stage load.
Power Output Stage: The principal notorious unpleasant "transistor sounds"
arise from several sorts of distortion in this stage. This applies to both A and B-class amplifiers. The most important HALCRO breakthrough is the virtual elimination of these unpleasant sources of distortion by a dual correction system which corrects for almost all of the unpleasant distortion inherent in this stage.
Printed Circuit Board: Six-layer boards provide excellent signal definition and minimal interference. Laid out with performance criteria, rather than for cosmetic reasons that can compromise performance.
Each stage is in itself a major breakthrough; for it would not be possible to attain the HALCRO super low distortion levels if any stage were not so.
