June 1st, 2021, 11:12 am
June 2nd, 2021, 2:17 pm
June 2nd, 2021, 2:30 pm
June 2nd, 2021, 3:02 pm
Pelliott321 wrote:I found this on the DIYAudio Forum
https://www.diyaudio.com/forums/analog-line-level/354213-po89zb-inline-dc-filter-smps-wall-warts-preamps-hpa-korg-nutube-etc.html
from the dialogue, this seems to be blessed by Nelson Pass and is a very simple circuit
June 2nd, 2021, 3:04 pm
Roscoe Primrose wrote:Tom, in your schematic, what's the purpose of R2?
June 2nd, 2021, 3:20 pm
tomp wrote:Roscoe Primrose wrote:Tom, in your schematic, what's the purpose of R2?
David Berning suggested that adding that would help damp any possible resonances between the filter output section and who knows what from the NUC. He certainly has had a lot of experience with switchers so I took his advice.
June 2nd, 2021, 5:00 pm
June 2nd, 2021, 5:36 pm
tomp wrote:David has had some crazy things happen in switch mode power supplies. In one amp he had a resonance develop between the power supply output and a bypass cap in the amplifier section input that blew a fuse that was higher rated than the current coming out of the power supply. He found that there was a resonant circuit that was passing enough current back and forth across the fuse that was higher than the DC draw and higher than the fuse rating. That is where damping can come in. I believe that the combination of the resistor and capacitor can help damp any resonance in the connection between the output and the NUC. The large electrolytic has enough internal impedance that it will probably not contribute to the problem and the monolithic ceramics are often specified especially in high gain Op Amp circuits because they also do not tend to resonate. The one capacitor and series resistor can act as a sink for resonant currents. That section may nor have any effect, but it couldn't hurt so I put it in.