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Old 10 December 2021, 23:29   #14
pandy71
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Join Date: Jun 2010
Location: PL
Posts: 1,974
Quote:
Originally Posted by ugrnm View Post
But that should be fine for pro line level, no? Vpp of pro line level is <3.5V.
Issue is not in level but in inability to isolate analog circuitry from digital part as they share same power line - unless Paula has embedded some fancy circuitry to provide true reference current/voltage to DAC's then you will have lot of unwanted sounds from digital circuitry on analog signal out lines.


Quote:
Originally Posted by ugrnm View Post
Hmmm, starting with R309, which ferrite bead value would you recommend then?
Something like https://eu.mouser.com/c/passive-comp...t%7C~Impedance

Highest possible impedance, maximum DC resistance bellow 1 Ohm, not sure about accurate Paula power consumption but i think ferrite bead should allow current not less than 500mA, ferrite bead tailored for rather low/standard frequencies...
Anyway even randomly selected ferrite bead will be probably better than resistor (strange that Amiga guys didn't selected ferrite bead instead 1 Ohm resistors - this can be explained by relatively new idea of ferrite bead and perhaps underestimation for signal quality expectations) - there is famous application note from linear technology (now owned by analog devices) https://www.analog.com/media/en/tech...tes/an101f.pdf - last page says everything important about ferrite beads - "megahurts to minihurts converter" this very good description for this small component capabilities.

Also avoid MLCC capacitors as most of them is piezoelectric and may produce audible interference's.
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