Kalliope

The Gryphon Kalliope is a digital-to-analogue converter designed to transfer musical signals from the digital domain into the analogue domain. The name refers to Kalliope, also known as Calliope, the eldest of the Muses in Greek mythology and the goddess of epic poetry and eloquence.

Signal conversion is central to every audio system. A phono cartridge changes the kinetic energy of a stylus moving through the micro-grooves of a vinyl record into an electrical signal, while a loudspeaker converts electrical input into acoustic output. The conversion of digital-source output into an analogue signal is another critical stage, since any information changed or lost at that point cannot be recovered later.

Gryphon Audio Designs developed the Kalliope DAC in response to the continuing refinement of digital sources and the rapid development of high-resolution digital audio formats.

Digital signal control

The phrase “Bits is bits” suggests that a digital system only needs to preserve the correct numbers in the correct order. Digital audio is instead a stream of numbers moving through time, so a correct number arriving at the wrong moment can be almost as problematic as an incorrect number. Gryphon Kalliope addresses timing errors, or jitter, through its circuit topology and custom-built components.

After digital-to-analogue conversion, an analogue filter removes high-frequency noise. Typical steep-slope “brickwall” filters can introduce temporal smearing, energy loss, reduced resolution and lower transparency. The Kalliope uses an advanced, minimalist single-component filter intended to avoid these adverse audible effects.

The analogue stage remains important after digital signal processing. Its circuit design, component selection, power supply and layout all affect the resulting signal. Gryphon Kalliope applies the company’s experience in analogue audio design to this stage.

Gryphon digital development

Kalliope follows Gryphon Audio Designs’ earlier work in digital audio. In 1998, the Gryphon CDP-1 CD player introduced 88.2 kHz asynchronous sample rate conversion, described as the first implementation of this technology. Gryphon Adagio, launched in 2001, and Gryphon Mikado, released in 2003, used 24-bit/96 kHz asynchronous sample rate conversion to preserve linearity and reduce distortion and noise.

The Gryphon Mikado Signature CD player, introduced in 2008, extended Gryphon’s dual-mono and fully symmetrical balanced design into the digital domain. It used 2 stereo DACs per channel in full dual-differential mode, operating at 32-bit/192 kHz. This configuration reduces the digital noise floor and supports a wide soundstage and sharply focused stereo image.

Gryphon Kalliope provides selectable 32-bit/210 kHz asynchronous sample rate conversion and uses a dedicated ESS SABRE ES9018 32-bit D/A converter for each channel. Each converter incorporates 8 individual D/A converters in dual-differential coupling.

Power supply and circuit layout

The design uses a strict dual-mono configuration, minimal internal wiring and separate, fully isolated power supplies for the analogue, digital and control/display circuits. Custom components include precision crystal oscillators and toroidal transformers.

Transformer windings for the digital and analogue sections are physically separated. A 4-layer printed circuit board uses a 70 mm copper trace for grounding, power distribution and signal transfer.

Each analogue channel has its own custom-built 65 VA toroidal transformer and 34,000 microFarad power capacitor banks. Rather than using a small number of large capacitors, Kalliope employs parallel-coupled clusters of smaller, high-performance capacitors. There are 28 capacitors in total, arranged to provide lower equivalent series resistance.

The heavily regulated, high-current power supplies are designed to provide power to all stages and use a configuration comparable with that found in an integrated amplifier.