Reply 20 of 23, by Tronix
Digital f***n noise still present, because SAA1099 has an open-collector PWM output, which we pull-up to +5V power rail and collect all the interference. So, i make new +5V analog path with help 78L05 linear regulator from +12V, as is done in many sound cards:
The interference is all gone! The sound immediately improved and became clear. Finaly, replace 78L05 TO-220 package with TO-92 and mount ampliefier. Sound quality still good without noise. Waiting for variable 10k resistor....