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Amadeus Audio




The Ypsilon DAC-100.

In the first CD players presented to the market in the 1980's, analogue filters were used at 22 kHz to reject out of band images of the audio signal. These filters cause a big phase shift in the audio spectrum and a slow response
to transient signals. They are also very expensive to implement, so the stop band attenuation was applied in the digital domain with so called digital filters.

In digital to analogue conversion these are interpolation filters, whereas in
analogue to digital conversion filtering is done with decimation filters. With interpolation filters, data is added mathematically and calculated from the originally retrieved data of 16/44 kHz. This process is called "oversampling". The result is that the sampling frequency of 44khz is increased to 96khz or
192khz and cheaper and more effective analogue filters can be used to reject the out of band noise. Even when this process is performed by powerful DSP (Digital Signal Processing) devices the end result is never like the originally retrieved data. Tremendous accuracy is required to retrieve clock (master, bit) data in order to keep jitter levels low. With interpolation filters, music sounds more processed and clinical. To avoid the problem of the high accuracy requirement of retrieved master clock data, a technique was used called "upsampling". The data in the DAC input are interpolated and re-clocked by a local clock generator, thus achieving low jitter since the clock generator itself is within a short distance of the DAC. Then data are sent to the digital filter and the upsampling is done again with interpolation. By not using interpolation filters, the sound is more natural, the image depth and dimensions are open and better defined. Also,
analog filters color the sound and affect dynamics in a negative way. Of course, by not using analog filters, the DAC's measurements include the out of band noise. But, it sounds more open, with bigger scale and a more analog-like presentation. Remember that the basic idea behind DSD technology was to get rid of the digital filters used in PCM. Unfortunately the industry did not embrace it but instead, kept interpolation in one way or another.

With the Ypsilon DAC-100, neither oversampling nor upsampling are used. A very linear and accurate chipset are implemented with paper in oil capacitors and I/V conversion is accomplished by a specially designed transformer, built in-house, using an exotic core material. As a result, there is no sonic character to the transformer. The analog stage of the Ypsilon DAC-100 uses a 6h30 valve for amplification and another type for valve rectification. By using only the best materials available in the DAC-100 and combining it with CDT-100 the sound can only be compared with the best analogue sources. You will be astonished

Tel: 07799812271 - E-mail: glyn@amadeus-audio.co.uk
1 Hoewood, Millglade, Small Dole, West Sussex