hardcorelinnie wrote:
fredrik wrote:
...(I Naims fall med högre frekvens (700kHz) och teoretiskt "bättre" jämfört med Linn DS i dagsläget (maxar 250kHz??*), ...
Jag har inte orkat dyka i detta så du får gärna utveckla gärna detta för oss andra.
Naim DAC överklockar CD/DAT signal 16x upp till en frekvens på 768kHz och använder 40 bitar för att lagra varje sampel.
Linn DS överklockar "bara" 8x och använder 35 bits aritmetik.
Från linn developer chat: http://www.linn.co.uk/ds_qa_archive2
All decoding is done at the native sample rate. The decoded PCM is then always upsampled to 8x44.4k/8x48k before it goes to the DAC. The upsampler uses an internal bit depth of 35. The output of the upsampler is then reduced to 24 bits to match the bit-depth of the DAC. The upsampling filters are fully upgradable via a firmware upgrade, but there are no immediate plans to change them. The current upsampling filters are linear phase and are fully attenuating at the Nyquist frequency.
Naim White Paper: http://www.naim-audio.com/download/Naim ... g_2009.pdf
Here we have oversampled the data 16 times: why not 8, 10 or any other convenient multiple? The 6th-order analogue filter used in the Naim DAC provides 36dB attenuation per octave. Working backwards, we see that with 8× oversampling applied to CD data the first image will appear at (8 × 44.1 – 22.05 =) 330.75kHz. At this frequency the analogue filter (see simulation below) provides about 125dB attenuation. Given that 24-bit data has a dynamic range of about 144dB (20log10(224)), if we use only 8× oversampling we won’t exploit the full potential of high-resolution music.