From TotalDac website:
"I listened to industrial DAC chips (from Analog Device, TI, Philips, Cirrus Logic, Wolson, AKM...). Some of them were NOS chips known for their nice sound such as TDA1541, TDA1545 (used in CD723), TDA1543, PCM56, AD1852 (used in Teac VRDS 25x), CS4328 (used in Helios Stargate), PCM1702 used in many high end CD players in the past, PCM1704... Some were really nice but never very accurate. I listened to them with and without oversampling whenever possible. I used a Pacific Microsonic PDM100 HDCD digital filter, one of the best digital filter. I also listened to many new DAC chips from TI and Analog Device in particular. It required micro controller programming most times. The sound was often a bit metallic. Lastly I could listen to a discrete R2R DAC made of simple 1% resistors. Musicality was there but some accuracy was missing. This was the start point of my ultimate DAC. I spent 2 years and 5 revisions of PCB to improve it and finally use 0.01% Vishay foil resistors and other improvements in the FPGA.
Jitter is very important for sound quality. It is related to the digital source and to the system clock. Today digital sources are sometimes computers so I wanted to make a DAC able to reduce the jitter of the source. An external clock is a common solution but it requires a digital source equipped with clock input, it exists but it is rare and specific. I wanted to make a DAC which can work with any digital source and any operating system and software when a computer is used. The only solution I could find is a solution rarely used, it is used only in some high end equipment based on FPGA and it uses a buffer memory (FIFO) to store about 0.1s of audio data at the digital source rhythm and output a stream at a local oscillator rhythm. At the beginning I used a low jitter crystal oscillator as a local oscillator. Of course there was a slight shift, as a consequence a crack appeared in the sound after a few hours. Practically this did not happen because the FIFO pointer was re-initialised between each CD track. The problem was elsewhere, I heard a kind of metallic sound when using these crystal oscillators. That's not surprising in fact because crystal are microphonic, there are even used to measure pressure. This problem disappeared when I used an RC oscillator instead but the RC oscillator frequency was not stable after hours. So I added a voltage control and the FPGA could control the RC oscillator frequency. A SPDIF receiver such as CS8412 or CS8416 already uses a voltage controlled oscillator but its command changes very quickly to track the input rhythm and so copies partially the jitter of the source. They have to track the digital source rapidly because they have a 80 nanosecond input to output delay whereas my DAC has a 10 mili second input to output delay"
The TotalDac is available both as a finish DAC or as a board which you can house our own. A positive review from 6moons.com appeared last week.
Another well known DAC guru, Alexandre Cerqueira, is using a TotalDac board to create a active crossover/tube preamp. See his website: http://www.ncforear.com.
Another well known DAC guru, Alexandre Cerqueira, is using a TotalDac board to create a active crossover/tube preamp. See his website: http://www.ncforear.com.
