For those that are curious as to the origin of the Cascade DACs design here is an overview its origins.
Eleven years ago, when I was designing the Select DACs electronics (the seventh DAC of my design that made it to production after the MSB Platinum DAC, Link DAC 3, credit card DAC (a promotional free giveaway at CES one year),Platinum DAC 4, Power DAC, and Analog DAC) I thought that I knew everything that was necessary for a DAC platform that would last for the longest time possible and have the best possible performance.
I had worked out the role of clocking (extensive experimentation into different clock architectures and measurements on the role of sound quality), processing (digital filters and data stream formatting), noise (the importance of digital isolation and conversion noise removal), conversion hardware (a software configurable analog system that could playback any format on the fly from single/multi-bit delta-sigma to PCM) and upgradability (input formats had changed rapidly and are, still changing today).
For Daniel it was going to be his second solo chassis design after the Analog DAC, and he was getting pretty good at that as well. What I did not anticipate at that time was just how electrically noisy things would become. I remember trying to diagnose a cluster of repairs for one of our transports, going back and forth with a couple customers to figure out why they were failing, and realizing that the problem actually stemmed from the video projector they were attached to.
With tens of volts of RF flowing over the HDMI cable, failure was inevitable. Many watts of continuous RF power were being dissipated by the protection circuitry which would eventually burn out the parts (this was obviously not good for sound quality either). That is when I decided to develop the Pro ISL optical interconnect, in my opinion the first high quality optical digital audio interface (toslink is not great and “ATT/ST glass” is also very problematic compared with even lowly s-pdif). Since then noise has only gotten worse. Ambient conditions and system interconnection noise have become “THE” nearly uncontrollable problem. Why is it that everyone is talking about isolators, routers, servers, cables, transformers and even battery power as being so important?
Well they are all nibbling at the edges of the same gigantic problem. Noise is leaking from our everyday audio and non-audio appliances into the delicate analog audio signals. Proliferation of solar inverters, LED lights, dimmers, communication equipment, displays/TVs, audio servers, computers and chargers are all contributing to this problem. Even the digital audio interfaces themselves generate and conduct objectionable noise despite faithfully transmitting the data they contain. This noise can be highly circumstantial meaning some customers don’t have much of a problem, but others are constantly struggling to get good sound.
Some even become disillusioned with digital audio altogether and go back to their LPs/tapes exclusively. This noise can propagate through the air, over the power lines and over any conductive cabling. I had designed a very good (two stages of isolation, one at each of the input modules, one stage at the DAC modules themselves) isolation system into the Select, but, I have found that “very good” is no longer sufficient today. The Cascade DAC shares much of the same design methodology of the Reference/Select but it takes noise isolation to the extreme.
Only the bare minimum of circuitry necessary to convert the raw data-stream to analog is present in the converter box and that box is heavily shielded physically, magnetically and electrically from its environment. No processing occurs in the Analog Converter box at all. Even the power to its internal relays (latching) is disabled when they are not switching to eliminate the problem of noise leakage from the power supplies driving their coils (a problem I discovered when prototyping the electrostatic headphone amplifier because of its extreme 141db of dynamic range). The outboard power supplies job is to heavily shield the converter box from the noise on the power mains (via onboard power filtering, magnetically and electrically shielded transformers, ultrafast rectifiers, inductor/capacitor filtering and ultra low noise, discrete regulators).
The Cascade Link is an advanced descendant of the optical Pro ISL interface which completely shields the conversion box from any upstream noise while simultaneously producing a vanishingly low amount itself. It also has a vastly increased data capacity to feed enough uncompressed data directly to the (8) DAC modules. The first time I heard the prototype Cascade in our electrically noisy facility I was shocked at how much of a difference this “no holds barred” approach to isolation was. Milling machine working hours, office computer use, solar inverter activity, music server software updates no longer had an appreciable impact on the music quality.
From there it has been a pleasure listening to and refining every last detail of the Cascade. We didn’t rush any of the details so each component had a significant maturation process, for example just the size and exact shape of all the stainless accents had prototypes machined and evaluated daily for weeks until we were completely happy with their exact shape and form. I spent hundreds of hours programming, evaluating and refining each of the playback formats supported this far (there are 17 individual data formats at launch, each with a different playback algorithm and unique DAC configuration).
I spent hours listening to the sound of the raw bit-stream of the Cascade Link (not music, the raw data bits themselves) to match the analog gaussian noise of analog electronics as closely as my hearing could discern (“real” not “artificial” noise) so as not to pollute the optical receiver with digital noise artifacts. A high resolution FLIR thermal camera was used to evaluate and refine the exact case contact to stabilize the temperature profile of the DAC modules.
We stacked and evaluated every configuration of the separate chassis to determine the optimal placement of the magnetic shielding for every one so that our customers could place the boxes anywhere they liked in their system without worry. Daniel even designed and machined custom fasteners to optimally hold the power transformers in place. All the while we would constantly debate and recenter each design feature to keep them focused and not unnecessarily complex or expensive. Cost no object performance, but without waste, is the philosophy we aspired to follow for the Cascade. Everything that was required for world leading performance and intuitive operation but nothing more.
In the end all our equipment is convectively cooled, but these days I never design for convective cooling within the case. Vented cases allow ingress of all sorts of stuff over years of service (believe me I have seen it all sorts of crazy contaminants) so we design conductive cooling solutions for all of the internal components to couple them to the casework, just for the sake of mitigating contaminant buildup, although it does assist with RFI mitigation as well (no case penetrations solely for cooling).
