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The Orthos XS operates in a push-pull pentode or triode mode and class A. The power supply was carefully implemented despite the more tolerant push-pull design. Quality took a significant leap forward due in part to the use of new precision-regulated power supplies. Benefits include increased dynamic headroom and a tighter more tuneful bass. The care bestowed on the power supply design is said to have brought vividness and a noticeable increase in agility and articulation. The balanced input stage keeps the noise floor vanishingly low. AC line filtration was enhanced and separate transformers, chokes and filters insure complete isolation between input and output stages.

Hirt uses electrolytic capacitors with large storage capacity to compensate for the loss in filtering when using resistors in lieu of inductors. Each Orthos XS has two separate low-noise insulated power transformers encased, fully damped and RFI/EMI shielded. A logic sequenced soft-start power up extends tube life. All passive components seem of premium quality such as high-speed coupling capacitors, gold-plated PCB and tube sockets with beryllium-copper spring pins.

Base specifications are bandwidth of 8Hz to 70kHz into 4 & 8 ohms, 1kHz input impedance of 47KΩ, input sensitivity of 1200mV for full power, S/N ratio of 98dB, dimensions of 35x61x25cm and weight of 50kg.

Sound. To my ears the new Orthos XS proved supremely transparent and revealing of subtle detail and small-scale signal. This high degree of transparency did not default into spurious artificial brightness or harshness. Contrarily to imperfect KT88 designs, the big Ayons were examples of sheer delicacy from the go. They did never sound dull and nor miss microdynamic or large scale voltage shifts. Their impressive depth and profusion of musical detail seemed effortless without the added artifice that many amplifiers inject to reach this level of accuracy.

The Orthos XS also delivered effortless high-speed musical transients whilst maintaining adequate delicacy of natural sound without artificial edge or sharpness. Compared to my Orpheus Thee M and Luxman M800a monos They might have tended to soften the grain of violins and voices but deftly avoided putting too much emphasis on the midrange or a euphonic rendering.

Articulation was clearly among the best I ever heard from tube amplification. These monos were able to delineate transients even on massive orchestral recordings such as the
Third Symphony of Saint Saëns without smearing the various details and instruments together. Realistic speed and pace were their most striking features. The Ayons thus achieve that very rare combination of being delicate and musically natural whilst being articulate and accurately precise. The two Orthoss XS had impressive reserves of dynamics which felt distilled with an uncommon sense of relaxed ease. I never had the sensation that the Ayons started to congest under loud or complex signals. Clipping levels seemed in fact quite unachievable.

My Austrian loaners exhibited that typical blackness which makes for a perfect rendering of dynamics and precise placement of each instrument in a three-dimensional soundstage. The level of silence provided was really impressive. The new Orthoss delivered one of the quietest noise floors I ever experienced with tube amplification very close to best solid-state realizations like big Mark Levinson. Thus overall clarity and transparency were outstanding for devices of this class. Each subtle textural detail and minor transient often buried and obscured were effortlessly revealed. The Ayons also delivered plenty of subtle imaging cues such as hall ambience, localization and depth information and even information about the air and space surrounding each performer on stage.

Accuracy of tone is not the strongest point of a KT88 push-pull design. Here the potential buyer will obviously not expect a 300B midrange. Gerhard Hirt nevertheless succeeded in tone which stands in my opinion above average for this class of amplifier. This may also depend on the choice of valves and associated equipment particularly the preamplifier. The Orthoss have a kind of honesty in the upper midrange that further helps the accurate depth layering and portrayal of concert hall ambience. They are very linear and never gave me the sensation of overemphasized treble or upper midrange.

The bass was rather rich, full and superbly defined. My loaners demonstrated excellent skills with rhythm and articulation. Their low register were never preeminent or boomy and clarity across the entire bandwidth was another strong feature of the Austrian amps. Accuracy of string attacks was impressive. I thought that my Orpheus Three M were amongst the best to get such energy and accuracy from transients but the Orthoss XS performed nearly as well with more subtle decays. My two Luxman M
800a amplifiers deliver less energy but a bit more density and texture on strings instruments.