pLudio skrev:galder skrev:Du kan ju alltid byta ut Rpi 3 mot Rpi 4 åtminstone, så får du lite mindre distorderad signal.
Den digitalt kodade ljudsignalen är självklart identisk mellan RPi 3 och RPi 4. Har man inga USB-problem med RPi 3 så vinner man inget på att uppgradera till RPi 4.
Du kan ha rätt, men jag tror inte John Westlake ( konstruktör av bla m-dac från Audiolab samt projekt-streamer håller med dig. )
Det finns dessutom flera oberoende testare på youtube som rapporterat att RPi4 låter bättre via USB än 3:an.
John Westlake angående 3:an :
https://www.avforums.com/threads/why-is ... i.2175090/Kolla inlägg 16 där John skriver mycket ingående om de fel som finns i 3:an .
” Basically its weakness are all based on Clock Phase Noise (Jitter) and local PSU noise (which directly impacts the Jitter performance) and also the resultant local RF emissions:-
1. The USB HUB / LAN IC is clocked by the CM3 SoC which has significantly higher jitter then an external Clock oscillator. More detrimental is that fact that clock phase noise is heavily correlated with the SoC software processing – resulting in Data correlated jitter.
2. The USB HUB / LAN IC PLL clock circuits are powered from the switching supply rail that also powers the SoC Memory, so as data is “processed” though the memory this causes modulation of the PSu Rail directly correlated with the Data patterns which then modulates the critical PLL in the USB HUB / LAN which is used as our USB “source” via this noisy PSU rail.
3. As one would expect little care has been taken with the quality of the 5V rail for USB DAC power – in fact its really pretty poor by “Audio” standards.
4. There are multiple “free running” switching regulators on the RPi PCB – whose clocks are not related to the USB clock Rate so there switching products are free to induced multiple / complex RF and Ground noise spurie in the system.”