Katerina is the version of the Reference Tube DAC built on the Burr-Brown PCM1704, a 24-bit chip from the mid-1990s and the last of the classic high-end ladder DACs. Dmitriy Gubchenko voices it with strong bass, detail and attack.
The Burr-Brown PCM1704
The PCM1704 is a 24-bit mono converter with laser-trimmed resistor ladders on the chip, arranged in sign-magnitude form: values on each side of zero are produced separately, so a quiet signal near zero switches only the low-order bits instead of passing through a transition of the whole ladder.
Like the other multibit chips of the five it delivers a current rather than a voltage, and a stereo converter uses two, one per channel.
Old stock
The PCM1704 has long been out of production. Every chip in use today is old stock; remarked parts circulate, so each one is checked before it is fitted.
Twenty-four bits, played as sixteen
In Katerina the PCM1704 converts the 16-bit / 44.1 kHz signal from coaxial S/PDIF as it arrives, without an interpolation filter or upsampling. The chip’s 24 bits do not turn Katerina into a high-resolution converter: it is built around the CD format, like every version of the Reference Tube DAC.
As in every non-oversampling design, the treble rolls off gently, by about 3 dB at 20 kHz, and image frequencies above 22.05 kHz reach the output stage. Our guide to NOS multibit DACs explains the trade-off.
Katerina among the five
The PCM1704 is commonly described as precise, with controlled bass and strong attack, and Katerina is the voice of the five with strong bass, detail and attack. Artemis on the earlier PCM63 is large-scale and weighty; Aphrodite on the Philips TDA1547 is dark, velvety and melodic. All five share the same chassis, input, output options and price. The stock output stage is solid-state; a tube stage on 6Zh4, EF14, EL8, AL4 or ML6 with a 5Ts4M rectifier is optional. Each unit ships with its own measurement report.