The emailer was Cees Ruijtenberg of Metrum Acoustics. "How are you? My compliments by the way for the new layout of your website! It may have seemed that for a long time there has been no activity from our company with no new products. As a matter of fact, we gave kept quite busy. For a year now we were focused on creating our own DACs, meaning we wrote certain specs and based on those tried to find components which would do the job. This began with identifying a ladder network. From there the next step was a digital interface to make the ladder network compatible with several audio formats like I²S for instance. Perhaps the most important step was the conversion from current to voltage. Of course we did measurements on the design but a lot of time was spent listening to evaluate the prototypes. Again there was a big gap between measurements and listening. We also found that there exists no NOS DAC in the world with good jitter measurements. But that is actually caused by using the wrong measurement methods. Later on I will describe this in a kind of easy-read white paper. The result is a very easily implemented high-end DAC module which we can use for our own future products but which will also be made available to other companies as an OEM replacement for the old and maybe exhausted stock of TDA1541 and similar chips. A single module can be used in single-ended mode whilst two will give you a fully balanced system. In the announcement document you will find more info but there is also a very detailed data sheet available for those who have to implement the modules in their own design.

"The Dac One is a modern high-precision replacement for old chips often used in 'non-oversampled' systems like the old TDA 1543 and TDA 1541. It is not a pin-compatible replacement but a way to build up a converter system which can meet today's best systems on sound quality. The Dac One is built up around a fast 16-bit very precise R2R ladder network. To match this ladder network to real audio formats, fast glue logic was added which makes the DAC compatible with RJ16, RJ24 and I²S standards. The Dac One is physically split up in two sections. The digital section runs on 5VDC whilst the analog section needs a symmetrical ±6V. Both positive or negative reference voltages can be used to give a fully symmetrical voltage or current swing. Like one-bit converters, the Dac One can handle 24 -bit formats due to forward control techniques as realized with our FPGA-based 'forward correction module'.
"There are two versions. The ladder network is designed as a current-output device. To obtain a voltage output requires an I/V converter. The current output from the R2R ladder is directly available on one of the output pins. In this version the ladder is connected to an I/V converter having a extremely fast 1500V/µs slew rate and a bandwidth of 500MHz. This approach gives a very open detailed sound without the restrictions of commonly used silicon. In case of the  voltage output, a passive 1st-order network is added to the I/V converter with a -3dB point at 70kHz. This filter also creates an output impedance of 100Ω in the audio band. The EVA motherboard shown above right is made to evaluate the Dac One module in single-ended mode. By connecting a transformer having 2 x 10-12VAC windings. the board is ready for use. It can handle S/PDIF data up to 192kHz and several other data formats by removing three jumpers like RJ16, RJ24 and I²S. Core specs are 16-bit resolution, max 1.5mA output current (current output version), 3V± max reference voltage for 2Vrms (voltage output version), -125dB noise relative to 2Vrms output (ma. digital input data) and -150dB @ 2Vrms for min. digital input data; 0.022% 2nd-order THD at 44.1kHz and 0.0025% 3rd-order THD with total power consumption of 91mW. More detailed information is available via info@metrum-acoustics.nl."