ЦАПы — Aries Cerat Helene

The Helene is the smallest digital-to-analogue converter made by Aries Cerat, and it borrows its technology from the larger converters of the brand's Kassandra series. It is a bit-perfect ladder design that applies no data processing, no upsampling and no oversampling, so every file is converted at its native sample rate and bit rate. The analogue side runs through a single-ended triode stage, and valves are also used to regulate the supply rails.

Key specs that matter

The Helene converts with eight R2R ladder converters per channel, running in parallel. The chips are Analog Devices AD1865NK parts working in current mode. Digital signals enter over USB, which accepts sample rates up to 384 kHz, or through S/PDIF, AES and BNC connections that can be used in any combination. The analogue signal leaves through either RCA or true balanced XLR sockets at an output level of 10 V. The unpacked unit weighs 40 kg.

Engineering and use context

A custom logic system controls the sync, data and work buses that feed the parallel converter banks. The Helene uses the SuperClock circuit found in the larger Aries Cerat models, which removes the need for an external word clock. USB and the remaining digital connections all pass through reclocker circuits driven by the internal SuperClocks, and the reclocker on the digital inputs can be bypassed. Current-to-voltage conversion is done by a specialised transformer wound on a custom ultra-high MU core, and this transformer directly modulates the bias circuits of the valve stage that follows. That analogue section works as a compact SET amplifier built around an E280F supertube, loaded by a custom output transformer. In the power supply, GZ34 valve rectifiers are combined with triple choke and film capacitor networks to produce low-noise voltage rails.

Pairing

With both single-ended and balanced outputs, the Helene can feed a preamplifier or a line input with either single-ended or balanced cabling. The choice of USB, S/PDIF, AES and BNC inputs lets a computer, a network streamer and a CD transport be connected at the same time, and the internal clocking means no separate master clock unit is needed alongside it.

Alternatives

A bigger converter from the same workshop is the Ithaka Minor, which runs 12 AD1865 ladder chips per channel into a Class A TriodeFet stage with a 1 ohm output impedance, fed from an external power supply built on two 400 VA toroidal transformers.