randytsuch Wrote: > Hi Dorkus > When you said snubber, at first I thought you were talking about the > putting RC's on each diode of the diode bridge. But, I think you are > talking about a RC filter, either before or after the voltage > regulator. I am guessing you put it before the regulator, after the > big lytic that would be after the diode bride, effective making a CRC > filter. >
hi randy, yeah, "snubber" is a bit confusing since it is often used on inductive loads or rectifiers as you mention. but in the most general sense, it is just a bypass capacitor damped with a series resistance. this is different from a CRC filter where the R is in series with the line - in a snubber the R is only in series with the cap. i was actually surprised that wikipedia has a decent concise explanation of snubbers: http://en.wikipedia.org/wiki/Snubber here's some more specific info: http://www.diyaudio.com/forums/showthread.php?threadid=56106 in carlosfm's diagram, the .47 ohm resistor in series with the 47uF bypass cap constitute the snubber. since it is just a general impedance compensation element (same idea as a Zobel in a speaker crossover), you could choose to add snubbers anywhere there is a reactive load or an inductive rise in output impedance - on the xformer secondary, before regulators, after regulators, etc... however one must be careful not to inadvertantly make matters worse by introducing a rogue pole in the whole mess, which could potentially cause ringing. usually the most advisable place is right after a regulator, where the impedance characteristics are hopefully known. unfortunately not many regulator datasheets specify output impedance vs. frequency, but the LM340T does, which may be why carlosfm from diyaudio prefers it. good ol' fashion trial and error can also be used, though that is obviously tedious. i really recommend playing with snubbers a bit - it's cheap, easy, and based on my quick experimentation highly effective. i really was skeptical that such small impedance changes could make much of an audible difference, but listening to my lightly (and not even properly) snubberized DAC last night i was again amazed at the improvements, at least in my relatively high-resolution system. YMMV though. power supply design really is an art that i am only beginning to scratch the surface of... when used in high speed, highly dynamic circuits (e.g. digital audio), one must really consider the supply to be a complex impedance network (xformers, caps, parasitics, etc.) combined with negative feedback amplifiers (regulators). batteries do not sidestep this problem as they have impedance and noise issues of their own. sometimes i wonder if the blissful ignorance of looking at supplies as pure DC was better... *sigh* -- dorkus ------------------------------------------------------------------------ dorkus's Profile: http://forums.slimdevices.com/member.php?userid=3373 View this thread: http://forums.slimdevices.com/showthread.php?t=19822 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
