"Most of the current and still considered top-line Burr-Brown/Texas Instruments DSD-capable DAC devices, including the latest 32-bit PCM1795, use FIR filters for DSD to analog conversion. That's true 1-bit processing in its purest form. The older now discontinued DSD1700 which Ed and Andreas ran in their first pure DSD converters used just one set of 8-tap FIR filters with fixed coefficients in a so-called double-differential architecture. The newer TI chips offer FIR filters with 4 sets of coefficients, allowing the designer to better optimize the final performance depending on the post-filtering techniques. Again, that's true 1-bit conversion at its best when it comes to SACD/DSD64 which, in my opinion, far outperforms the DSD1700 and probably is the reason why it was discontinued.

"While our reference DSD-M uses my own 20-tap differential FIR filter with custom Lundahl transformers and differential tube output stage, the DSD-S utilizes only the DSD part of the CS4398 devices. These offer two paths for DSD processing. One is Direct DSD which sends the stream directly to the SCF switched capacitor filter for the purest DSD conversion similar to a FIR filter. Such an option is also seen in the latest AKM converters. But such pure DSD conversion leads to far higher noise figures which calls for relatively steeper analog filtering. The second path in the CS4398 is an on-chip 50kHz 'Scarlet Book' low-pass filter and a non-decimating volume control. Both are further processed by the internal Delta/Sigma modulator to achieve better noise performance. This is all done without PCM conversion whilst DSD integrity is preserved. To my knowledge, Cirrus Logic are the only company offering DAC devices featuring such technology. Patent info is here.  
Stock Pioneer PD-50 player

"Since volume control is otherwise impossible in the DSD domain, to my understanding, other companies always convert DSD to a sort of PCM flavour in order to offer attenuation. Apparently the CS4398 does not. Since I wanted a truly versatile relatively affordable but still pure DSD converter with lossless volume sans PCM conversion, the CS4398 was the best option. My first re-designed Philips SACD1000 units and some of the Denon units already used the CS4398. I am quite familiar with it. After so many years, I have implemented knowledge and technologies that significantly improve the final sonic character of a design using the CS4398. Of course more than 10 years ago already this part sounded quite nice for DSD which impressed many audiophiles who were into SACD then. To make sure that there are no negative effects at all whilst attenuating, my hybrid attenuator achieves almost 50dB attenuation with only 12dB used in the CS4398 whilst still offering 0.5dB steps. At lower than -50dB levels, only digital attenuator is used but that is well below any normal listening."

"I usually ship the DSD-S with all inputs set to -47dB to prevent problems if connected directly to amplifier/s. This one I set to 0dB (full output) for the coax1 and USB inputs so you can try with a preamp first. When you are ready to go amp-direct, please make sure to decrease the volume to -47 or -50dB. For headphones connected directly to the DSD-S output, please set to -25dB before plugging them in. What is in the box aside from the DSD-S: 1/ a power cable that is a €300 value. It is worth auditioning, in my opinion. 2/ my own USB cable that is unique in a way since it is completely unshielded. According to customer feedback, it outperforms USB cables costing $2'500 in terms of tone naturalness. Please note that this is not a regular USB cable and will not work with other USB devices because it misses the +5V supply line. It has two ground lines instead. 3/ two SDHC memory cards with two albums that you may like, recorded in DSD. One is Martin Taylor Spirit of Django and the other is Ali Akbar Khan's Indian Architexture. 4/ a home-brew RCA to 6.3mm phone adaptor. It has OFC wires and WBT RCA plugs. I will try to figure out a nicer looking adapter for customers who are interested. Probably it will be better if I use a 4-pin XLR plug too but I did not have any on hand. The DSD-S does not require a driver for Mac. It will show up as an XMOS audio device. For playing DSD, please set to "DoP1.0 standard" in Audirvana or PureMusic preferences. There should not be any upsampling, volume control or other processing for PCM. The USB input supports 32-bit integer mode. 

APL-branded Schuko power cord, headphone adaptor, unshielded USB cable, metal remote wand.

"Finally, I would like to mention the extremely talented digital audio specialists from Audiopraise.com when it comes to the DSD-S development history. Though many audio manufacturers will not admit to help from third-party developers, I am so impressed with the guys at Audiopraise that I feel it is an absolute must to give them well-deserved credit for helping me with the design of the proprietary DSD modulator, the 'Magic Digital Filter', encrypted data transmissions and other projects we worked on together. These guys remind me of the days I worked in the professional division at Sony Electronics in San Jose, California, dealing with $3.5 Million JumboTron installations, $1.5 Million HD Digital Video effects consoles etc. The cheapest things were $75K Digital Betacam video recorders. After dealing with such equipment, audio electronics really seem like baby toys. Similarly the specialists at Audiopraise have extensive experience with much more sophisticated products such as broadcast quality, professional and military equipment, thus are capable of designing unique digital audio-related software and hardware. My highest recommendations for Audiopraise!"