Some of the technical areas that CAD feels are key to reproducing a natural non fatiguing sound quality are:
Time Domain Response
The key reason why we use Resistor Ladder DAC technology in our 1543 MKII DAC is due to the excellent time domain response that a Resistor Ladder DAC offers. This is best explained with two graphs.
Impulse response is when we apply a digital input to a DAC that consists of a short impulse (~5usec) of maximum level (~0dB) and then look at the analogue output of the DAC.
CAD believes the analogue output impulse response of a DAC is one of the key attributes of DAC architecture that relates to sound quality. Here is an example of the analogue output of a two DACs to an impulse input:
You will notice that the DAC output in the graph on the left has what is called pre and post ringing and the graph on the right for a non-oversampling (NOS) Resistor Ladder DAC does not.
The ringing shown on the left graph above is just an example. There are many different types of ringing and there are ways to reduce the ringing through filtering. But at CAD we believe phase issues caused by filtering also cause sound quality issues. CAD does not use any filtering on the ouptut satge of the 1543 MKII DAC.
Here at CAD we believe the sound quality results of Resistor ladder DAC technology along with no filtering and no oversampling produce a preferable sound quality over other options.
One of the first questions we usually get about our 1543 MKII DAC is “what DAC chip do you use?” We agree that the DAC chip is important, but most people do not realise is that the power supplies are at least as important! We have spent an enormous part of our research on developing the power supplies for our 1543 MKII DAC. Not all DC power supplies are the same and we developed a type of shunt/class A of our own proprietary design that gives an extremely low output impedance along with extremely high slew rate.
Slew rate is how quickly the power supply can supply current to the load without the voltage level changing. The low output impedance of our design helps this and we feel this characteristic is crucial for digital audio.
At this point it is important to note that that CAD feels this combination of fast transients with no ringing that the Resistor Ladder DAC technology allows along with power supplies that have an extremely high slew rate and can deliver current very quickly is one of the reasons the 1543 MKII DAC sounds the way it does.
Most people will agree that if you hear noise coming out of your speakers that isn’t music that is a bad thing! But when we speak about noise here at CAD we are talking about a different thing all together. We of course have developed our products so that noise within the normal hearing range of 20Hz to 20KHz is reduced in our products, but we have gone much further than that. We feel that noise in the frequency range of 100’s of KHz up to GHz range can effect sound quality. All of our products include designs and materials to reduce noise in this frequency spectrum from entering (or exiting) on the mains power connections. We also work hard on reducing this noise with in our prodcuts on the DC power supplies, digital and analogue signal lines. We believe it is crucial to reduce this noise on the audio components signal ground and on the mains power earth connection. We believe in this so much we have come out with the Ground Control product line just for reducing high frequency noise on signal ground and mains earth.
The 1543 MKII DAC contains five independent transformers that drive five independent power supplies. Three of these power supplies are just for the USB interface! The reason we do this is to try to reduce the noise from one circuit from entering another circuit within the DAC. This type of noise is called intermodulation noise and we have worked very hard to minimize this within our 1543 MKII DAC, our Audio Transport and USB cables. The CAD Audio Transport has many different noisy circuits running at different frequencies and we have used similar technology that is in our 1543 MKII DAC and some different technologies for the CAD Audio Transport to minimize intermodulation noise.
If you look at any CAD product you will not see many inputs, outputs, switches or knobs. Our 1543 MKII DAC has no power switch and the mains power cable is permanently attached. In our opinion the best switch or connector is no switch or connector. We feel that generally speaking if you can get the job done properly with fewer parts the sound quality is better.
We also realize that a simple design that achieves your goal can be much more difficult and time consuming to accomplish than a more complex design. It is somewhat like writing a one page paper on a subject can be more difficult then writing a 10 page paper. This logic is a core principle at CAD and can be seen in all our products.