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I am wondering if anyone have tried using snubber cap with soft recovery FRED? Will this combo benefit anything at all?I am planning to try it on my DV414, I guess I will find out when the parts is here.
Thank you in advance for any information.
Kevin.
elan120 wrote:I am wondering if anyone have tried using snubber cap with soft recovery FRED? Will this combo benefit anything at all?
Since the FREDs are already apparently well-damped and don't exhibit the ringing of regular rectifier diodes, I don't see that adding a snubber cap would help. In fact, it may undo what the FREDs are acheiving.
The ringing you get with conventional rectifiers is the result of the diode's capacitance in combination with the leakage inductance of the power transformer's secondary. Placing caps across the FREDs you could end up creating the very problem you're using the FREDs to avoid in the first place.
Also, simply adding a cap across a conventional rectifier really does nothing to damp the resonance (the ESR of the capacitor is far too small to provide any significant damping). It just lowers the resonant frequency by adding more capacitance to the diode's capacitance. You can only damp a resonance with resistance. That's why properly designed snubber networks use series RC (resistor/capacitor) networks across the diodes instead of a simple capacitor.
se
Thanks for the info. After a little more investigating, I think I will stick with just the soft recovery FRED.In the meantime, what is the difference between HEXFRFED, FRED, and soft recovery FRED?
Kevin.
elan120 wrote:In the meantime, what is the difference between HEXFRFED, FRED, and soft recovery FRED?
Nothing really. They all refer to the same basic type of device. HexFRED is International Rectifier's trade name for their line of FRED diodes, FRED is a more generic term for Fast Recovery Epitaxial Diode, and soft recovery is one of the characteristics of some types of FREDS.
se
Elan,Putting a cap across a rect. bridge is a common tweak to improve the bridge's performance. I don't see a problem in using a snubber w/ FREDs. How large a cap are you intending to use?
PS
Peter,I will be using 0.1uF cap across the FRED. In addition, I am also plan to install o.1uF cap across the input AC power terminal as well, do you think this will help reducing the noise, or just something to do?
Thank you.
Kevin.
See www.magnan.com -> tweaks for good recommendations regarding
mains filtering, with brands of capacitors annotated.
Alternatively, look at tnt-audio for the same things, but
without the capacitor brands.
I followed Magnan's recipe, and achieved significant noise reduction
as well as digital edge reduction in the CDP (modded Marantz 63)
Sergei
Elan,Check the archives for Joh Rische's DIY line filter info. You can easily add a decent (and low cost) line filter that will clean up the main power to your equipment. BTW, don't forget, use AC rated caps for main line power filtering.
elan 120 wrote:I will be using 0.1uF cap across the FRED. In addition, I am also plan to install o.1uF cap across the input AC power terminal as well, do you think this will help reducing the noise, or just something to do?
The 0.1uF cap across the AC line would provide for some simple RF filtering which would be useful.
se
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