ЦАПы — Rotaxis Core64 DAC

The Core64 DAC is a resistor ladder DAC from Rotaxis Audio. It is built around a proprietary architecture that its designer calls the PulseAxis Ladder. Rotaxis describes it as a time-domain focused, passive resistor ladder converter without feedback, noise shaping or digital compensation.

Key specs that matter

The ladder has 24 bits of resolution. Each bit is represented by a group of precision-matched resistors, typically 64 for each exponentially weighted bit, which gives the Core64 its name. The resistors are arranged in circular rings, the PulseAxis Array. Switching runs at a base clock of 11.2 MHz with sub-clocking near 100 MHz. The analogue output stage is fully discrete, runs in Class A and is transformer-coupled through Lundahl transformers, which also breaks ground loops between the DAC and the preamplifier.

Engineering and use context

Most modern DACs use delta-sigma modulation, noise shaping and oversampling digital filters, which convert the signal to a high-rate low-bit stream and rely on digital processing to reach low noise and distortion. A resistor ladder instead builds each output level directly from weighted resistors switched by the bits of the digital word. The accuracy of a conventional ladder depends on how precisely each resistor matches its ideal value, and errors produce distortion that is worst at low levels. Rotaxis addresses this by building each bit from many matched resistors, typically 64, so that individual errors average out, and the company claims the averaging exceeds laser-trimmed monolithic ladders. Arranging the resistors in interwoven rotational rings is intended to reduce electromagnetic interference, thermal drift and crosstalk between bits. The bits do not switch statically. They fire in timed quarter-clock quadrants, grouped by current weight with the most significant bits first, so each resistor settles before the next activates, which avoids overlap glitches and errors at zero crossings. The company notes that the architecture is scalable, with a future entry-level model using 32-level rings. With no noise shaping, the converter keeps its errors at the analogue level rather than shifting noise to ultrasonic frequencies.

Pairing

The Core64 suits systems built around a transport or streamer with a digital output, driving an analogue preamplifier.

Alternatives

Rotaxis has no other DAC on sale yet, since the Core64 is the company's first converter.